Field Guide to Insects and Diseases

Southwestern Region Field Guide

Learn about flora and fauna in the Southwest.

Field Guide to Insects & Diseases of Arizona and New Mexico

Most forest insects and pathogens in the Southwest are naturally occurring components of ecosystems and play an important role in dynamic processes. They affect short- and long-term vegetative structural diversity, provide food and habitat for animals, and contribute to biological diversity. These organisms, along with fire, are among the major disturbance agents in the Southwest. Outbreaks of forest insects and diseases can result in shifts in forest composition and structure. The degree of shift depends upon the particular insect and/or disease and on the condition of the ecosystem affected.

The actions of insects are often easily observed as their populations can quickly expand under favorable climatic conditions. Some insects are significant natural disturbance agents, capable of altering forest succession. For example, bark beetle populations can increase dramatically under drought conditions and cause large-scale tree mortality. In contrast, indigenous tree pathogens increase gradually and their presence and effects may go relatively unnoticed. Although most people see dwarf mistletoe in our forests, few realize that it is the primary agent of growth loss and will gradually kill trees. Insects and pathogens often interact, as is seen when diseased trees are attacked by bark beetles.

A key to insect and disease damage is provided in the Guide to Forest Insects and Diseases, directing the reader to the appropriate insect or disease section. A description for each insect and disease includes hosts, damage, symptoms, biology, and effects or impacts. A list of references cites resources used to compile this guide.

Please refer to your local forest service, forest health zone office, state forest health specialist, cooperative extension agent, or state forester for information concerning specific control measures.

Guide to Forest Insects and Diseases

Our insect and disease field guide is divided into sections based upon the type of insect or disease or grouped by the type of damage they cause. This key helps users to navigate the field guide using where on the tree the damage occurs. Within each damage location, the main categories of agents that can cause that type of damage are linked.

Defoliating Insects. Affected needles with a reddish cast, insects or signs of their feeding present. Needles and buds are partially or totally consumed. Caterpillar or beetle-like insects usually present on foliage in early spring or summer. Leaves chewed, mined, skeletonized or webbed. Viewed from a distance, affected trees have a brownish or yellowish cast.

Sap-Sucking Insects and Mites. Curled or discolored foliage. Whole insects or cast skins and small (1-2 mm long). Cottony tufts, galls, and honeydew sometimes present.

Galls Caused by Insects. Abnormal, misshapen, swollen or spherical growth on needles or leaves, or in the bark or twigs. Insect larvae or frass present inside the galls.

Bud and Shoot Insects. Malformed, enlarged buds on young growth, commonly encountered on terminal buds of branches. In some cases, multiple leaders result.

Foliar Diseases (Conifer Needle Diseases and Hardwood Leaf Diseases). Foliage yellow, brown, or spotted (insects largely absent); orange, yellow, or black pustules or other fungal fruiting bodies present. Fruiting bodies are very small.

Abiotic Disorders. Foliage or buds yellowing, browning, or dying after exposure to early or late frosts, air pollutants, drought, or winter damage; entire crown may show signs of stress or die as a unit; cause of the damage may not be apparent but signs of insect or disease agents are generally absent.

Galls Caused by Insects. Abnormal, misshapen, swollen, or spherical growth in the cones or seeds. Insect larvae or frass present inside the galls.

Moths and Midges. External evidence of insect activity is difficult to see. Galleries are small in diameter and are commonly found within the cone axis, cone scales, and seeds. Boring dust is reddish to light brown and fine.

Cone Rust. Enlarged cones on Chihuahua pine, with orange spores under papery uter covering.

Witches' Brooms. Prolific sprouting of adventitious buds on branches infected with mistletoe or fungi.

Needles retained on those caused by dwarf mistletoe.

Needles cast on those caused by fungi, only to reappear he next year.

Cankers and/or Animal Damage. Large patches of dead bark on live trees, sometimes exposing wood; often on main tree bole; fruiting bodies of fungi may be present.

Strips or sections of bark removed by animals, fungi follow wounding.

Stem Decay. Wood is hollow, pitted, spongy, breaks into crumbly pieces, or is stained in color. Fruiting bodies of fungi may be present. Older trees, or those physically injured in the past usually affected.

Bark Beetles. Insect activity characterized by boring dust and/or resin on bark and around base of trees. Galleries commonly found under bark and usually less than 0.6 cm in width, at times into the sapwood, rarely penetrating the wood. Boring dust reddish to light brown and fine.

Wood Borers. Larval borings are usually granular. Galleries penetrate into the sapwood and, at times, into heartwood of weakened or recently killed trees or logs.

Oystershell Scale

Abiotic Disorders. Globe-shaped, large, woody growths or swellings on branches or stems of ponderosa and various hardwoods (burls).

Root Diseases. Entire crown shows signs of stress (yellowing foliage, needle or leaf loss, stress cone crop) or dies as a unit; wood or root tissues are killed or decayed and may have fungal structures; fruiting bodies of fungi may be present at base of tree or on the ground nearby; trees may die standing, snap at the lower bole, or uproot with a characteristic small root ball and extensive decay in the broken stubs of primary roots; fallen trees in disease centers tend to lie in a random pattern.

Windthrow. Insectionidual or patches of trees exhibit stem breakage or uprooting with a large soil plate and primary roots attached; fallen trees typically lie parallel to one another in a similar direction of the windstorm; signs of disease agents may be present (e.g. root disease).

Non-infectious Disorders. Dead and dying trees found in small or large groups, not usually solitary trees. Entire crown of tree shows signs of stress and dies as a unit similar to damage by root disease. Fruiting bodies of pathogenic fungi usually absent, but weakly pathogenic and saprophytic fungi (those restricted to dead tissues) and secondary insects may be present.

Navigating the Field Guide Visual Catalog

Our insect and disease field guide is divided into sections based upon the type of insect or disease or grouped by the type of damage they cause. This visual catalog allows users to navigate to the sections of the field guide by the major categories. Within each group are the various specific damage agents.

Animal Damage

Domestic livestock and wild ungulate browsing can cause severe damage to forest regeneration. Aspen forests in particular have suffered extreme damage.

Rocky mountain elk are considered the primary threat to the long-term survivability of aspen, because they impact aspen in so many ways. Elk have a height advantage over other ungulates and are able to reach higher in the crowns of saplings, often snapping the main bole and killing it.

Elk rub antlers on small diameter trees (7 to 15 cm), creating wounds that allow entry for canker and wood decay fungi. Elk also gnaw or strip the bark (a.k.a. barking) of larger trees, allowing the entry of insects such as the bronze poplar borer.

Identifying Animal Damage

Select a box below to learn more about identify animal damage.

Black bears rip wide strips of bark from trees, often starting at about 1 m from ground line. They forage on the cambial zone in the lower bole by removing or peeling the bark with their claws and scraping the vascular tissue with their incisors. Trees are often girdled and die from one stripping, but sometimes survive. The wound left in partially girdled trees can lead to extensive decay. Bears also break branches on oak trees to access acorns.

In the White Mountains and Pinaleño Mountains of eastern Arizona, black bear strip the bark of southwestern white pine and subalpine fir greater than 25 cm in diameter. This activity is so widespread in some areas that it is difficult to find a large undamaged southwestern white pine or subalpine fir.

Black bears rip strips of bark from trees and feed on the cambium.
USDA Forest Service, Southwestern Region

Although squirrels and porcupines have a variable diet during the growing season, in the winter they chew through the outer bark of branches or boles and feed on cambium. Coniferous trees are preferred.

Squirrels target smaller branches and often target dwarf mistletoe infested limbs.

Porcupine injury can be locally damaging because the animal tends to stay in a small area, girdling and killing the tops of many trees.

Since porcupine populations tend to fluctuate, trees often form new leaders and grow to maturity.

Squirrels more often chew on branches and select those infested with dwarf mistletoe.
Porcupine chew through the bark and feed on the cambium.

Domestic livestock and wild ungulate browsing can cause severe damage to forest regeneration.

Aspen forests in particular have suffered extreme damage.

Rocky mountain elk are considered the primary threat to the long-term survivability of aspen, because they impact aspen in so many ways.

Elk have a height advantage over other ungulates and are able to reach higher in the crowns of saplings, often snapping the main bole and killing it. Elk rub antlers on small diameter trees (7 to 15 cm), creating wounds that allow entry for canker and wood decay fungi.

Elk also gnaw or strip the bark (a.k.a. barking) of larger trees, allowing the entry of insects such as the bronze poplar borer.

Ponderosa pine browsed by ungulates.
Elk snapped these saplings while feeding on foliage after a protective fence was removed.
Elk "bark" mature trees with their teeth.
Aspen suckers are heavily browsed by ungulates, especially elk.

Sapsuckers feed primarily on the sap of trees, moving among different trees and tree species on a seasonal basis.

Insects are attracted to the sweet sap exuding from sap holes and are often captured and fed to young sapsuckers during the breeding season.

When feeding, sapsuckers puncture the bark in horizontal lines around tree limbs or main stems. These punctures sometimes serve as entry points for stain or decay fungi.

Intensive feeding by sapsuckers sometimes results in severe tree damage and mortality, even to large ponderosa pines.

Sapsuckers drill parallel rows of holes and feed on sap and insects caught in the sap.

Bark Beetles

Bark beetles are one of the most destructive insects in western coniferous forests. It has been estimated that 90 percent of insect-caused tree mortality and more than 60 percent of the total insect-caused loss of wood growth in the United States is due to bark beetles. In the Southwest, bark beetle killed trees were scattered over more than 2 million acres between 2001 and 2003.

The Southwest has a large complex of bark beetles composed of many genera and species. Frequently, several species are found attacking the same host tree and, therefore, it may be difficult to discern what species initiated the attack. Although species of Dendroctonus are the most notorious tree killers in the western United States, Ips species also play a very important role in pine forests of the Southwest.

Bark beetles derive their name from their habit of living and mining between the bark and wood of trees and shrubs. Adults excavate egg galleries in bark phloem. All bark beetle life stages are spent in the phloem, inner bark and bark, except when adults leave the tree in which they developed to fly to new host material. Bark beetles feed on the phloem during adult and larval stages.

Most bark beetles are considered secondary mortality agents because they prefer weakened host material. However, during environmental conditions favorable for beetle development, populations may build up rapidly and successfully attack healthy trees. Most bark beetles have a symbiotic relationship with blue-stain fungi. The blue stain fungi can completely penetrate the sapwood within a year. The fungi occlude the outer conducting tissues in the xylem that halts upward water translocation. This action, plus that of the bark beetle feeding, causes the death of a host tree.

Bark beetles produce chemical compounds called pheromones that are used to communicate with other beetles. Aggregation pheromones cause beetles to congregate in certain areas and mass-attack trees. Anti-aggregation pheromones cause beetles to disperse to neighboring trees or other areas. Pheromones of many bark beetles have been identified and synthetically produced. Both aggregation and anti-aggregation pheromones have been effective to mitigate impacts caused by some bark beetles in the western United States.

Crowns of successfully attacked trees turn from green to yellow to reddish brown. This color change, an indication of a dying tree, may occur from a month to more than 2 years after successful attack depending on the temperature, moisture conditions, and density of beetles in the tree. Close inspection of infested tree trunks will show either small globules of resin, small holes through the bark, or reddish boring dust in bark crevices and around the tree base. The removal of bark from infested trees will reveal two types of galleries, egg and larval. Egg galleries constructed by adult beetles are rather uniform in width. Larval galleries depart at right angles from egg galleries and increase in size as the young grow.

Scientific Name (s)

Dendroctonus barberi (Hopkins)

Host

Ponderosa pine

Symptoms/Signs

Larval feeding in the inner bark and adult mating and egg laying creates mazelike galleries. Entrance holes, reddish dust in bark crevices, and pitch tubes are indicators of attack. Exit holes are created when the mature beetle leaves the host. Trees, which have been successfully attacked by beetles, are most noticeable when the foliage begins to fade from green to yellow to red to gray. Also, infested trees often exhibit signs of woodpecker feeding activity in the bottom half of the bole. Needles fall off approximately 1 year after the initial attack.

Biology

Adult beetles usually begin flight and attack of suitable host trees in late spring or early summer and continue until cold weather begins. Females produce from one to three broods a year. Eggs are laid in niches along galleries. When the eggs hatch, the larvae feed in the inner bark working away from the egg gallery.

Effects

The direct effect of successful attack is tree mortality. Usually, the beetles breed in and kill scattered, overmature, slow growing, decadent, or diseased trees and trees weakened by stand stagnation, lightning, fire, or mechanical injury. This tree mortality may be considered part of the normal ecological process of succession during which a forest matures and replaces itself. Epidemics can affect ponderosa pine ecosystems by reducing the density and size distribution of its host, and altering species composition and stand structure.

Similar Insects and Diseases

Other bark beetles attacking ponderosa pine. Southwestern pine beetle egg galleries can be distinguished from other beetles by their maze-like appearance.

Woodpecker activity ("flaking off of bark") on ponderosa pine indicating that Southwestern pine beetle larvae are in the outer bark.
Kennenth E. Gibson, USDA Forest Service
Pitch tubes indicating Southwestern pine beetle attack are frequently small in size (<1/4 inch, 6.4 mm).
USDA Forest Service, Southwestern Region

Scientific Name (s)

Ips spp.

Hosts

Pines and spruce

Symptoms/Signs

In standing trees, fading tops of large trees or whole crowns in small trees can be indicators of Ips infestation. Other external evidence consists of accumulations of boring dust in bark crevices and at the base of the tree. Occasionally pitch tubes can be found on the trunk. Characteristic egg galleries may be found under the bark, slightly engraving the sapwood, hence the common name engraver beetle. In slash, look for boring dust and galleries.

Adults are small cylindrically shaped brown beetles a few millimeters in length. They possess a pronounced concavity at the rear end of the elytra that is bordered on either side by three to six tooth-like spines. Larvae are white, legless grubs.

Biology

Beetles produce 2 to 4 generations per year, depending on climate, species, and elevation. In spring, adult beetles emerge from material infested the previous fall and fly to attack new hosts. Beetles prefer fresh debris from logging, construction activity or natural events, but during outbreaks living trees may be attacked.

Effects

Bark beetles in this genus have the potential to kill thousands of pine trees during short-lived outbreaks in Arizona and New Mexico. Pine mortality is frequently noticed in drought years. Pinyon ips (I. confusus) killed millions of drought-stressed piñon across the Southwest from 2002 to 2004. Similarly, the pine engraver beetle (I. pini) and the Arizona five-spined ips (I. lecontei) killed millions of ponderosa pine during the same time span throughout Arizona. Some outbreaks are associated with human activities that create large amounts of fresh pine debris or that weaken trees. These insects are also beneficial, creating snags and providing a food source for other animals.

Similar Insects and Diseases

Other bark beetles may be found in southwestern pines. They may be distinguished by egg gallery characteristics and adult appearance. Ips egg galleries possess a nuptial chamber—an enlarged excavated area—with one to many galleries radiating from it. The egg galleries are free of frass. Dendroctonus galleries vary by species in shape but lack the nuptial chamber and are packed with frass. Ips adults display a pronounced concavity at the rear end of the elytra, which contains three to six spines on either side. Dendroctonus adults on the other hand have a rounded declivity with no spines. Frequently, both Dendroctonus and Ips species occur within the same tree with Ips species typically located in the top half of the bole and Dendroctonus in the bottom half.

Landscape level piñon mortality caused by pinyon ips in New Mexico.
USDA Forest Service, Southwestern Region
Boring dust in bark crevices near base of pinyon ips attacked piñon.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dendroctonus ponderosae (Hopkins)

Hosts

Ponderosa pine, white pines

Symptoms/Signs

External evidence on green infested trees consists of pitch tubes. On successfully attacked trees, these are small and numerous. Pitch tubes on unsuccessfully attacked trees are larger in size (around 2 cm in diameter), typically white, and widely scattered over the trunk. During drought years, infested trees may not produce pitch, and external evidence consists only of boring dust. These are referred to as blind attacks. Later, foliage on successfully attacked trees fades to yellowish green, to sorrel, red and finally brown. Under the bark, egg galleries are straight, vertical, and packed with boring dust. They range from 10 to 122 cm in length. Adult beetles are brown cylindrically shaped beetles about 4 to 7.5 mm long. Larvae are small white grubs with tan head capsules.

Biology

The beetle produces one generation per year. Adults begin attacking trees in early July and the attack period can extend into September. Females initiate attacks and release pheromones to attract males. Beetles create egg galleries in the inner bark and females lay eggs. In 1 to 2 weeks small larvae hatch. Generally they overwinter as small larvae. Larvae resume development the following spring and when mature, excavate oval cells in which they transform into pupae and then adults. Adults then bore out and attack new trees. In the Southwest on ponderosa pine, this insect is found primarily on the Kaibab Plateau in northern Arizona and in northern New Mexico. It can be found on white pines throughout the Southwest.

Effects

The direct effect of successful attack is tree mortality. Epidemics can affect ponderosa pine ecosystems by reducing the density and size distribution of its host, and altering species composition and stand structure.

Similar Insects and Diseases

Several other bark beetles may be found in Southwestern ponderosa pine, including other Dendroctonus species and engraver beetles. These may be distinguished from mountain pine beetle by their egg gallery characteristics and adult appearance. Egg galleries of the western pine beetle are maze-like, and those of the roundheaded pine beetle are vertical and slightly sinuous. Galleries of engraver beetles possess a nuptial chamber with one to several galleries radiating out from it. Engraver beetle egg galleries are free of frass. Ips adults display a pronounced concavity at the rear end of the elytra that possesses three to six spines on either side. The elytral declivity on Dendroctonus adults is rounded and does not possess any spines.

Ponderosa pine mortality caused by mountain pine beetle.
USDA Forest Service, Rocky Mountain Region Archives
Egg and larval galleries of mountain pine beetle. Note that egg galleries have an initial 'crook' or 'j' and then run vertically up the bole. Larval feeding galleries are perpendicular to the egg galleries.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dendroctonus adjunctus (Blandford)

Host

Ponderosa pine

Symptoms/Signs

Reddish brown boring dust is present in bark crevices and numerous pitch tubes are observed on the bark at entrance holes. In heavily attacked decadent trees, pitch tubes are often missing or very small. Later, the foliage fades from green to yellow or bright red, and eventually a dull brown. Woodpecker activity on the trunk is also a good indication that bark beetles have attacked the tree.

Biology

Adult roundheaded bark beetles attack and colonize susceptible trees in October and November. Females initiate the attack producing an aggregation pheromone drawing large numbers of beetles to the tree. The beetles chew through the bark and excavate a chamber in the moist tissue beneath the bark. Males enter the chamber and mating occurs. Female beetles then excavate horizontal tunnels in the inner bark region for 25 to 50 mm and then longitudinally with the grain an average distance of 300 mm. Eggs are laid individually in niches on alternate sides of the egg galleries, which are packed with frass. The larvae mine across the grain in the inner bark until in the third instar and then bore into the outer bark to complete development.

Effects

Roundheaded pine beetles attack, colonize, and kill trees in the southwestern United States and Mexico. Periodic outbreaks have killed large numbers of ponderosa pine in southern New Mexico and southeastern Arizona. In 1950, 16,000 pole and sawtimber-sized trees were infested on 2,500 acres near Cloudcroft and 400,000 pole-sized ponderosa pines were killed on 150,000 acres from Mayhill to Ruidoso in 1971. Similar outbreaks occurred during the 1990s in the Sacramento Mountains in southern New Mexico and the Pinaleño Mountains in southeast Arizona.

Similar Insects

The roundheaded pine beetle is similar to other Dendroctonus beetles, Ips beetles, and other members of the subfamily Scolytidae. Dendroctonus beetles are distinguished from each other mainly by their unique egg galleries and, in the case of the Douglas-fir beetle and spruce beetles by the host species they attack. Dendroctonus beetles are distinguished from Ips beetles by their rounded posterior ends and galleries, which are packed with frass. In contrast, the posterior ends of Ips beetles are slightly concave with and have several to many small spines and the runways (egg galleries) are free of frass.

Aerial view of ponderosa pine mortality caused by roundheaded pine beetle in the Pinaleño Mountains, Arizona.
USDA Forest Service, Southwestern Region
Ponderosa pine mortality caused by roundheaded pine beetle in the Pinaleño Mountains, Arizona.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dendroctonus mexicanus Dendroctonus frontalis (Zimmerman) and (Hopkins)

Hosts

Chihuahua, Apache, ponderosa pines

Symptoms/Signs

Presence of reddish brown boring dust caught in bark flakes and crevices around tree; numerous pitch tubes on the bark at the entry point of the tunnels. In heavily attacked decadent trees, pitch tubes are often missing or so small they can only be seen up close. Later, the foliage begins to fade, turning from green to yellow or bright red, and eventually a dull brown. Woodpecker activity on the trunk is also a good indication that bark beetles have attacked the tree.

Adults are dark reddish brown, cylindrically shaped beetles approximately 3 mm in length. Larvae are white, legless grubs. The morphology of southern pine beetle and Mexican pine beetle are very similar and, therefore, are difficult to tell apart. Taxonomists use the seminal rod of male beetles as the distinguishing characteristic.

Biology

Although southern pine beetle has many generations in the southeastern U.S., it likely has only one to two generations per year in the Southwest depending on elevation and climate. Adults construct winding galleries in the inner bark, where eggs are deposited in individual niches on each side of the galleries. The larvae mine for a short distance before boring into the outer bark where they pupate. Mexican pine beetle is thought to have a similar biology.

Effects

Southern pine beetle and Mexican pine beetle killed large numbers of Apache and Chihuahua pines throughout 1999-2001 in the Chiricahua Mountains of southeastern Arizona. Pine mortality ranged from single trees to large groups of more than 100. Southern pine beetle has been collected from traps in northern Arizona.

Similar Insects and Diseases

Southern pine beetle and Mexican pine beetle can be distinguished from other pine bark beetles by the shape of egg galleries and beetle morphology. Southwestern pine beetle egg galerries are similar in appearance; however, larval feeding galleries on the inner bark are absent.

Chihuahua pine mortality caused by southern pine beetle in Chiricahua Mountains, Arizona.
USDA Forest Service, Southwestern Region
Egg and larval galleries of southern pine beetle. Note that egg galleries are S-shaped that crisscross one another in the inner bark and on the wood surface.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dendroctonus valens (LeConte)

Hosts

Pines

Symptoms/Signs

The best indicators of red turpentine beetle attack on pines are:large pink-white pitch tubes on the lower bole; accumulations of reddish brown sawdust at the base of the tree and in bark crevices; and accumulations of cream to pink colored crystallized resin granules at the tree base. The egg galleries under the bark are fairly wide and linear to irregular in shape. Galleries extend downward from the entry hole 7 cm to 1 m and may even extend into large roots.

Adults are reddish brown, cylindrically shaped beetles approximately 8 mm in length. Larvae are white, legless grubs.

Biology

The number of generations varies from 1 to 2 years in the coldest portions of its range to 2 to 3 generations per year in the warmest areas. Attacks are made in the lower bole of pines. Attacks occur throughout warm weather but peak by midsummer. These beetles often attack trees scarred by fire.

Effects

Through repeated attacks this beetle can sometimes kill trees; however, more often it weakens trees, predisposing them to fatal attack by other bark beetle species. In successful attacks, a patch of bark ranging from a few square cm to a square m or more may be killed. Red turpentine beetles frequently colonize fire-scorched ponderosa pines.

Similar Insects and Diseases

This beetle is distinguished from other bark beetles by the large size of the pitch tubes, galleries and the beetle itself.

Granola-like crystallized resin material can occur around bases of pine trees attacked by red turpentine beetle.
USDA Forest Service, Southwestern Region
Red turpentine beetle frequently attacks fire-damaged ponderosa pine as indicated by pitch tubes and frass.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dendroctonus rufipennis (Kirby)

Hosts

Engelmann spruce is principal host, blue spruce is an infrequent host

Symptoms/Signs

External evidence on green infested trees consists of entrance holes in the bark and occasional pitch tubes. However, pitch tubes are often indicative of an unsuccessful attack. Red boring dust from entrance holes usually accumulates in bark crevices around the bases of infested trees. Woodpeckers frequently remove large sections of bark looking for larvae to feed on. About 1 year after attack, needles of infested trees usually turn a yellowish green and fall, though some may remain green until the second year. Needles do not turn a reddish color like those on bark beetle infested pines. Under the bark, egg galleries are vertical and slightly groove the xylem. Egg galleries range from about 6 to 30 cm long. Adult beetles are cylindrically shaped and 4 to 6 mm long. They are generally dark brown to black with reddish brown wing covers; however, older adults are usually entirely black. Larvae are creamy white, cylindrical, legless grubs. Larvae reach a length of about 6 mm. Pupae are creamy white and similar in size to the adult.

Biology

Spruce beetles generally produce one generation in 2 years; however, generation time can take from 1 to 3 years. Adults emerge from May through July and begin attacking new host trees. Eggs hatch and larvae develop during the summer. Broods overwinter as larvae or callow adults and complete development to mature adults by the following August. Spruce beetle attacks standing trees, windthrown trees, or logging residuals. It prefers large diameter, green downed material to standing trees. Populations are affected by a number of factors including the number of susceptible hosts, natural enemies, and extreme cold.

Effects

The direct effect of spruce beetle attack is tree mortality or in some cases strip kill, when only a vertical section of the bole is attacked. Strip attacked trees often die in subsequent years. Spruce beetle epidemics can have both immediate and long-term effects on spruce-fir forests. The immediate effects include changes in stand structure and composition. The longer-term effects come from successional changes that result from microclimate changes as well.

Similar Insects and Diseases

The most common associates are in the genus Ips . In New Mexico, I. pilifrons sulcifrons is the most common, while in Arizona, I. pilifrons utahensis is found most often. Ips beetles frequently infest the upper (exposed) portion of downed material, while spruce beetle favors the shaded material. Ips egg galleries differ from those of spruce beetle by containing a nuptial chamber and by being free of frass.

Flaking of bark caused by woodpeckers indicates spruce beetle larvae in the outer bark of Engelmann spruce.
USDA Forest Service, Southwestern Region
Remnants of spruce beetle galleries on a downed log.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dendroctonus pseudotsugae (Hopkins)

Host

Douglas-fir

Symptoms/Signs

Reddish-orange frass is the first sign that a tree has been attacked. At times, the most evident sign of attack is the clear resin exuding from entrance holes on the upper portions of the stem. Pitch flow, however, is not always present on successfully attacked trees. Needles of successfully attacked trees change from green to yellow to sorrel to reddish brown in the year following attack. Egg galleries run parallel to the wood grain and are 20 to 25 cm long. Adult beetles are stout, cylindrically-shaped, and 4 to 6 mm long. The head and thorax are black; the wing covers reddish brown, becoming darker with age.

Biology

The Douglas-fir beetle has one generation per year. Although adult flight times vary by year, most new attacks occur in late spring to early summer. Broods develop under the bark throughout the summer and early fall. Adult, pupal, or larval life stages can overwinter. Brood that develops to pupae or adults by winter usually emerges between April and June. Overwintering larvae emerge as adults in summer. A small percentage of adults that overwinter will re-emerge from the spring-attacked trees and attack additional trees in the middle of summer. Typically, late-season attacks account for less than 20 percent of all attacks in one season.

Effects

The direct effect of successful attack is tree mortality. At low or endemic levels, the beetle infests scattered trees that are infected with dwarf mistletoe and/or armillaria root disease, injured by fire, or stressed by defoliating agents. During outbreaks, groups of 100 or more attacked trees are common. Douglas-fir beetle epidemics can have both immediate and long-term effects on mixed conifer forests. Immediate effects include changes in stand structure and composition. Successional (long-term) changes result from alterations in microclimate.

Similar Insects and Diseases

Other bark beetles, Scolytus monticolae and Douglas-fir pole beetle Pseudohylesinus nebulosus), often occur in large branches, boles of pole-sized trees and the top of trees killed by Douglas-fir beetle. They may be separated by gallery patterns and characteristics of adult beetles.

Galleries of Douglas-fir pole beetle on small diameter Douglas-fir. Galleries are short, longitudinal and often with two branches.
USDA Forest Service, Southwestern Region
Successful attack by Douglas-fir beetle is indicated by a) frass (boring dust)in bark crevices, spider webs, or at base of Douglas-fir and b) pitch streaming.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dryocoetes confusus (Swaine)

Host

Subalpine fir (corkbark fir)

Symptoms/Signs

Small entrance holes and boring dust are usually difficult to detect on green standing trees, but pitch flow may be evident. Under the bark, egg galleries lightly etch the surface of the wood. Egg galleries radiate from a central nuptial chamber. Attacked trees generally turn yellow-red within a year. Needles on a beetle-killed fir may remain for more than 4 years. Adults are shiny, dark brown, cylindrical beetles about 2 to 5 mm long. The posterior end of the elytra is abruptly rounded with no spines.

Biology

Little is published on the biology of this species; however, it is thought to have a 1- to 2-year life cycle. The lower to mid bole of standing trees is usually selected for attack. This species is moderately aggressive and capable of killing older and/or weakened trees. Occasionally cut or fallen trees are attacked.

Effects

The direct effect of successful attack is tree mortality.

Similar Insects and Diseases

Other bark beetles attack subalpine fir, including species of Scolytus and Pseudohylesinus . They may be separated by gallery patterns and characteristics of adult beetles. Western balsam bark beetle attacks are frequently associated with fir infected by root diseases.

Corkbark fir mortality caused by western balsam bark beetle on the Sandia Mountains, New Mexico.
USDA Forest Service, Southwestern Region
Corkbark fir mortality caused by western balsam bark beetle on the San Francisco Peaks, Arizona.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Scolytus ventralis (LeConte)

Hosts

True firs

Symptoms/Signs

Freshly attacked green trees have tiny holes in the bark, reddish-brown boring dust in bark crevices, and streams of clear pitch exuding from entrance holes. Needles change from green to yellow-green to sorrel and then red to brown. Larvae, pupae, and egg are found in the inner bark; egg and larval galleries deeply score the wood, creating characteristic horizontal egg galleries and vertical larval galleries. Adult beetles are small, shiny, black beetles about 4 mm long. The abdomen is incurved at the rear.

Biology

In warm locations, the fir engraver completes one generation and a partial second generation each year. In cooler sites, the beetle needs 2 years to complete its life cycle. Adult flight occurs throughout the summer, but peaks in July and August. Fir engravers overwinter primarily as young or mature larvae. In the spring, they feed for a short period and then construct pupal cells at the end of their galleries.

Effects

Fir engravers are a major mortality agent of true firs, usually attacking pole-sized to sawtimber-sized trees. Outbreaks often occur during and following droughts. Root diseases are often associated with attacked trees. The fir engraver can also breed in slash and wind-thrown trees. Flagging (death of branches) may occur on fir trees that have been only partially attacked.

Similar Insects and Diseases

Other bark beetles attack subalpine fir, including species of Dryocoetes and Pseudohylesinus . They may be separated by gallery patterns and characteristics of adult beetles.

White fir mortality caused by fir engraver on Mormon Mountain, Arizona.
USDA Forest Service, Southwestern Region
Egg and larval galleries of fir engraver. Galleries are horizontal with two branches radiating out from entrance point.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Pityogenes spp., Pityophthorus spp., Pityoborus secundus

Hosts

Pines and other conifers.

Symptoms/Signs

Trees attacked and colonized by twig beetles exhibit fading needles on twigs and branches, and twig and branch dieback throughout the crown. Tan sawdust is produced around the attack sites. On smaller twigs and branches, most of the cambium is mined beneath the bark. Small, star-shaped egg galleries generally occur under the bark of the larger branches and small trunks.

Biology

Adult twig beetles are about 3 mm long and dark brown. Most species have a rounded rear end, but a few have a pair of short spines. The larvae are fat, white, C-shaped grubs with light brown head capsules and feed under the bark. Most species have 2 to 4 generations per year, depending on local conditions.

Effects

Typically attacks and kills small twigs and branches of drought stressed or otherwise weakened pines and other conifers. Although twig beetles are generally considered of secondary importance, under favorable conditions they may develop in sufficiently high numbers and attack and kill small trees. Pityogenes carinulatus killed thousands of young ponderosa pine in 1967 in New Mexico as a result of populations increasing in thinning and logging slash. Twig beetles infested high numbers of young piñon in 2002, 2003, and 2004 across New Mexico and Arizona.

Similar Insects and Diseases

See Ips discussion. Most twig beetles have elytral declivity and egg galleries that are somewhat similar to Ips; however, twig beetles are smaller in size and are typically found in branches and very small diameter trees.

Mortality of piñon regeneration killed by twig beetles near Los Alamos, NM.
USDA Forest Service, Southwestern Region
Pitch tubes of twig beetles on piñon are typically very small (<1/8 inch).
USDA Forest Service, Southwestern Region

Scientific Name (s)

Phloeosinus spp.

Hosts

Arizona cypress and junipers

Symptoms/Signs

External evidence consists of twig killing (called flagging), or whole trees fading. Under the bark, egg galleries are simple and longitudinal, 2 to 7 cm long, usually engraving the wood rather deeply. Egg niches are usually rather large and conspicuous. Larval galleries wander away from the parent galleries.

Adults are reddish brown to black, shiny beetles ranging in size from 2 to 4 mm long. Larvae are small white grubs, with brown head capsules.

Biology

One to one and a half generations are produced per year. Attacks occur in spring and summer. Adults and larvae feed in the inner bark in galleries. Newly emerged adults feed on the pith of twigs of living trees prior to constructing egg galleries. Often twigs are hollowed out completely and killed.

Effects

These beetles are typically not aggressive and are generally found attacking branches, trunks, tops, and limbs of weakened, dying, or felled trees. Occasionally outbreaks occur during drought.

Similar Insects and Diseases

This is the main bark beetle genus attacking cypress and juniper. There are some woodboring beetles that attack these trees. Bark beetles are distinguished from woodborers by the shape and location of the galleries and size of the adults and larvae. Galleries of woodborers extend both in the bark and wood. Woodborer larvae and adults are larger than bark beetles.

Extensive mortality caused by cypress bark beetle north of Clifton, Arizona.
USDA Forest Service, Southwestern Region
Mortality of Leyland cypress near Sedona, Arizona, caused by cypress bark beetle.
USDA Forest Service, Southwestern Region

Bud Shoot Insects

Injury to buds and shoots may be caused by caterpillars, weevils, bark beetles, midges, aphids, or scale insects. Some of these insects also feed on other plant parts such as foliage, cones, and branches. By far the most frequently observed damage to pine shoots is caused by tip moths and shoot borers belonging to the order Lepidoptera (moths and butterflies).

Shoot insects affect trees by damaging terminal or lateral shoots. Such damage typically reduces height growth and deforms the tree. Forked branches or multiple leaders often result from a previous year’s insect damage. Seedlings and saplings are most susceptible to damage by shoot insects. Trees above 2 m in height rarely sustain significant injury. Young seedlings are often prevented from growing taller than herbaceous competitors, resulting in mortality.

Most of these shoot insects are important in young, intensively managed stands or replanted forested areas. The susceptible stage of hosts is predictable and managers can plan accordingly to minimize impacts caused by shoot insects.

Select a box below to learn more about identify bud shoot insects.

Scientific Name (s)

Rhyacionia spp.

Host

Ponderosa pine

Symptoms/Signs

Insect appearance varies between species. R. bushnelli adults have a wingspread of 10 to 15 mm; forewings are mottled yellowish gray and reddish brown. Larvae are yellowish with black heads, and about 9 to 12 mm long when mature. R. neomexicana adults have a wingspan of about 24 mm. Forewings are irregularly banded with transverse bars of dark gray, blackish and brick-red scales on the inner two-thirds of the wing. Larvae are usually orange in color with dark brown to light tan head capsules and are about 12 to 16 mm long when fully developed.

Biology

Larvae mine inside new shoots in spring and early summer, killing them. Both lateral and terminal shoots are attacked. Larvae initially mine needles and then bore into the shoot. Pitch tents, frass, and silk webbing are all signs of tip moth activity. Once in the shoots, larvae feed between the pith and the bark, eventually hollowing out the shoot.

Effects

Larvae mine in the phloem and xylem of lateral and sometimes terminal shoots. Small trees, those less than 2 m tall are most susceptible. Shoots are killed by the attacks. Repeated attacks slow growth and cause crooks, forks, multiple stems, and spike tops. Tip moths rarely kill established trees outright, but attacks can affect survival of young planted seedlings.

Similar Insects and Diseases

See Western pines shoot borer and ponderosa pitch nodule moth.

Closeup of damaged ponderosa pine shoot caused by pine tip moths.
USDA Forest Service, Southwestern Region
Damage of ponderosa pine shoot caused by pine tip moths. USDA Forest Service, Southwestern Region
Adult pine tip moth.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Eucosma sonomana (Kearfott)

Host

Ponderosa pine

Symptoms/Signs

Adults are moths with coppery-red forewings marked with two bright gray transverse bands and a wingspread of about 20 mm. External symptoms include shortened needles and stunted terminal growth. Following emergence of the larvae, exit holes can be found near the center of the shoot. In the year following infestation, a distinct swelling can be seen around the stem, near the exit hole. Occasionally terminals break off where the stem is weakened by the exit hole.

Biology

Eggs are laid on elongating shoots in spring. The larvae feed in the pith of these shoots, vacate in late spring, and drop to the ground to pupate. There they remain dormant through the winter and hatch as adults the following spring.

Effects

Larvae mine only in the pith of the shoot. Usually shoots remain green for at least a year after attack, however, in some cases shoots are killed outright. Most often shoots live, but become stunted. Frequently, lateral shoots overtop affected shoots and a crook or a fork results. The main result of infestation is reduced height growth, about 25 percent of one year’s vertical growth per attack. Depending on management objectives, this may or may not be important. The insect occurs at low population levels.

Similar Insects and Diseases

See pine tip moths

Larva of the western pine shoot borer. Note that larval feeding is restricted to the pith region of the shoots.
USDA Forest Service, Intermountain Region Archives
Damaged (top) and undamaged (bottom) shoots of ponderosa pine caused by western pine shoot borer larvae. Note 'bottlebrush' appearance of damaged shoot.
Michael R. Wagner (Northern Arizona University)

Scientific Name (s)

Retina (= Petrova) arizonensis (Heinrich), R. metallica (Busck)

Host

Piñon

Symptoms/Signs

Attacks are characterized by fading branch tips and small nodules of pitch formed at the insects feeding sites. The pitch nodules are hollow balls of pitch 13 to 25 mm long, round, smooth, and light purple to red in color. Pitch nodules usually occur at the crotch of two or more twigs.

Biology

Small, rusty-brown moths emerge through holes in the pitch nodule in late June and early July. Eggs are laid on the needle sheaths of the current year’s foliage. Newly hatched larvae feed on the young needles before boring into the bark at nodes or whorls of twigs or branches. Full-grown larvae are about 13 mm long, reddish-yellow in color with a black head and a dark area behind the head. Pupation occurs inside the pitch nodule in June. The pupae move just below the pitch surface before they emerge as adults.

Effects

Attacked twigs and branches are killed. Leaders are occasionally damaged and forked trees may result.

Cocoon of ponderosa pitch nodule moth.
USDA Forest Service, Southwestern Region
Damage caused by the piñon pitch nodule moth.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dioryctria spp., Synanthedon spp.

Hosts

Piñon, ponderosa pine, and occasionally Douglas-fir and true fir

Symptoms/Signs

Pitch moth attacks appear as large masses of pitch that form at the wound site, but some species of Dioryctria can damage the cone or shoots. The pinyon twig moth, D. albovittella , can cause significant damage on young pion. Bark moths typically produce less pitch.

Biology

Pitch moths require 2 years for one generation to mature, overwintering as larvae each winter. Bark moths require only 1 year for a generation to mature, overwintering as eggs or larvae. Eggs are laid in bark crevices or near mechanical wounds on the bark. Newly hatched larvae tunnel under the bark forming irregular galleries or elongated gouges in the sapwood. Pitch moth larvae feed on pitch the tree produces in response to their tunneling. Oozing pitch masses 25 to 75 mm in diameter cover entry holes and conceal larvae and their destructive tunneling. Full-grown larvae are 15 to 25 mm long, dirty white, yellow, orange, green, or light brown. Bark moth larvae feed on the inner bark and when full grown, are marked with rows of dark spots.

Effects

Larger branches, limbs, and trunks of young trees are attacked. Repeated attacks can seriously weaken and kill branches. The most severe damage is to trees under 6 m, especially in urban areas. The insects are rarely a problem on larger trees or in the forest environment.

Damage caused by pitch moth.
USDA Forest Service, Southwestern Region
Damage to piñon caused by D. albovittella at Sunset Crater NP, Arizona.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Styloxus bicolor (Champlain and Knull)

Hosts

Juniper and Arizona cypress

Symptoms/Signs

The juniper twig pruner is a small longhorned beetle (Cerambycidae). The adult is 7 to 11mm long and has a reddish-orange head and brownish to black body. Larvae are small, white roundheaded borers.

Closeup of damage to juniper shoots caused by the juniper twig pruner.
USDA Forest Service, Southwestern Region
Damage to junipers caused by the juniper twig pruner.
USDA Forest Service, Southwestern Region

Cankers

Canker-causing fungi are common on hardwoods, especially aspen. Canker fungi are often the primary cause of aspen mortality because aspen bark is soft living tissue, extremely susceptible to wounding and subsequent infection by canker fungi. Disturbances such as selective logging, campsite construction, and recreation abuse can increase the incidence of canker diseases. Although the majority of canker-causing fungi described below occur on hardwoods, the last fungus discussed occurs on conifers. Canker-causing stem rust fungi are discussed in another section, Rust Diseases of Conifers.

Scientific Name (s)

Ceratocystis fimbriata Ellis &Halst.

Host

Aspen

Symptoms/Signs

Cankers are target shaped with concentric ridges of dead callus. Older cankers typically have a central area of dead wood surrounded by a series of bark calluses. These callused areas may be concentric in outline, but usually are irregularly shaped and ragged in appearance because of the massive callus folds and flaring dead bark. Bark and exposed wood darken, resulting in a black canker.

Biology

Ceratocystis fimbriata can infect through the epidermis of leaf blades, petioles, and young stems; but trunk wounds are considered to be the primary places of infection. Several species of beetles have been found to carry the fungus and are believed to vector it. Infection first appears as a circular necrotic area on the trunk around a fresh wound or branch junction. During cambial growth in the spring, the tree forms a callus at the margins of the canker, which temporarily walls off infection. The fungus invades the new cambium and inner bark during the tree’s next dormant season and kills a new zone of tissue. This process is repeated each year until the canker, consisting of successive rings of dead bark and wood, is formed. The fruiting structures, perithecia, are formed in the spring along the border of the canker on tissues dead at least a year. Spores ooze from the perithecia in sticky masses and are often vectored to other wounded trees by insects. Boring insects are often found in cankered areas. There appears to be a genetic predisposition to infection, as some aspen clones are more susceptible to infection than others.

Effects

Ceratocystis fimbriata seldom kills large trees since trees generally grow faster in circumference than black cankers enlarge. However, it is possible for several cankers to coalesce and girdle a tree. The greatest damage from this disease is stem deformation and subsequent decay that can result in bole breakage.

Similar Insects and Diseases

Sooty bark is also black in color and may form a target like pattern as it progresses but does not cause discrete callus tissue formation or flaring bark that is associated with black canker. Black canker also lacks the black, crumbly, sooty inner bark characteristic of sooty bark canker.

Figure 1. Early stages of black canker on sapling (left). Large black canker on mature aspen stem. Note the concentric circle pattern indicative of black canker infection.

Scientific Name (s)

Encoelia pruinosa (Ellis & Everh.) Torkelson & Echkblad

Host

Aspen

Symptoms/Signs

Young cankers appear as slightly sunken areas with near normal bark color. Dead bark eventually falls off and reveals the black, sooty and crumbly inner bark diagnostic for this canker. Beneath the inner bark is a distinctive, black, feather-like pattern on the wood surface. The perennial cankers form a band of light gray bark that remains attached at the margin of each annual zone of expansion giving the tree a barber pole appearance. Gray to black leathery cup-shaped fruiting bodies develop on the inner bark along the canker margin. The wood beneath cankers is light gray.

Biology

The fungus infects trees through wounds and invades the inner bark and cambium. Cankers develop rapidly, extending as much as 1 m in length and 0.3 m in width in a year, however, the mean annual extension is about 45 cm vertically and 16 cm horizontally. The cup-shaped fruiting bodies—apothecia—develop on the surface of old dead inner bark and open when wet. Spores are forcibly ejected and wind disseminated when moisture and temperature conditions are favorable. These spores can cause new infections.

Effects

Encoelia pruinosa, the causal agent of sooty bark canker, is considered the most lethal and aggressive pathogen of aspen in the West because it can kill trees of all sizes in 3 to 10 years; some mature trees have been observed to die in 4 to 5 years. Sooty bark canker is found mainly on the larger dominant and codominant trees older than 60 years, in the middle elevational limits of aspen. It is more common in stands disturbed by partial cutting, construction, camper damage, or animal damage.

Similar Insects and Diseases

Cup-shaped fruiting bodies of sooty bark canker.
USDA Forest Service, Rocky Mountain Research Station
Black strips on aspen bole indicate infection by Encoelia pruinosa.
USDA Forest Service, Rocky Mountain Research Station

Scientific Name (s)

Cryptosphaeria lignyota (Fr.:Fr.) Auersw

Host

Aspen

Symptoms/Signs

Young infections and canker margins are orange to light brown. The cankers are long (3 meters or more) and narrow (2-10 centimeters wide), appearing as grayish depressions in the bark, with callus ridges forming at the edge. Dead bark adheres to the canker face. Inner bark is black and sooty with obvious fibers and small, light-colored flecks (<2 mm). Light orange, tiny asexual fruiting bodies may form near the edge of the canker. Clusters of black, flask-shaped sexual fruiting bodies (perithecia) develop beneath bark dead for more than 1 year. Cryptosphaeria lignyota also causes stain in the sapwood and heartwood and causes a yellow-brown, mottled decay.

Biology

Spores of C. lignyota are released during wet weather and infect fresh wounds in the inner bark and wood. The fungus eventually colonizes sapwood and heartwood, causing discoloration and decay, before penetrating the bark and causing a canker. Brown, mottled decay develops in the central part of the column of discolored wood. Mortality occurs not from bark necrosis as it may seem, but because the pathogen kills a large volume of sapwood.

Effects

Trees up to 15 centimeters d.b.h. may be killed within 3 years, with older trees taking longer to girdle. Branch cankers are often found on large trees, where they girdle the branch and enlarge onto the trunk. The decay associated with the canker predisposes infected trees to wind breakage.

Similar Insects and Diseases

Bark that has been dead for more than 1 year from C. lignyota is black, stringy, and sooty-like, similar to sooty bark canker (Encoelia pruinosa). However, they are easy to distinguish, because of the lenticular-shaped fruiting structures and barber pole design of sooty bark canker, both lacking in a Cryptosphaeria canker. In addition, sooty bark canker is not associated with discoloration and decay of the sapwood and heartwood.

Cryptosphaeria colonizes sapwood and cambium.
Thomas E. Hinds (USDA Forest Service, Rocky Mountain Research Station)

Scientific Name (s)

Entoleuca mammata (Wahlenb.) J.D. Rogers &Y.M. Ju

Host

Aspen

Symptoms/Signs

Young infections occur as slightly sunken, irregular, yellowish-orange areas around wounds or branch stubs. The underside of diseased bark appears laminated or mottled black and yellowish white. White mycelial fans form under the bark and are most evident at the top and bottom edges of the canker. Gray fungal pillars (asexual fruiting bodies) form beneath loose, blistered bark. Later, patches of gray-black, crust-like mounds form on the wood. These mounds contain perithecia, sexual fruiting bodies. The papery outer bark sloughs from older infections, exposing a blackened, crumbly inner bark. The cortex in the central portion of older cankers cracks in a checkerboard fashion, sloughing off in small patches.

Biology

In the humid Lake States area, the fungus invades the sapwood and trees often die before they are completely girdled because sapwood decay beneath a trunk canker predisposes the tree to wind breakage. In the arid Southwest, however, breakage is not common. Cankers on large trees in the Southwest may attain ages of 20 to 50 years before tree death. A live 1 m d.b.h. aspen tree in Arizona was observed with a Hypoxylon canker extending from the ground to a height of about 12 m, only half-girdling the tree. There appears to be a genetic predisposition to infection, because some clones are more susceptible to infection than others within the same geographic area.

Effects

Hypoxylon canker is the most important canker disease of aspen in the Lake States region where it is estimated to cause mortality of 1 to 2 percent of the standing aspen volume. While this disease causes serious damage and mortality in localized areas of the Southwest, mortality rates are likely much lower than those observed in the Lake States.

Similar Insects and Diseases

Figure 2. Hypoxylon canker forming on an aspen tree. Note the roughened checkerboard appearance of the canker (left). Small grey and black stroma which produce fruiting bodies of Entoleuca mammata.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Cytospora spp.

Hosts

Aspen, cottonwood, alder, Gambel oak and other riparian species

Symptoms/Signs

Young cankers on smooth bark appear as brownish-yellow sunken areas. They are often irregular in outline and range from diffuse to slightly target-shaped. Later, the bark often splits at canker margins, the inner bark turns black, and wood beneath the canker is stained brown and water soaked. Black, pimple-like, asexual fruiting bodies (pycnidia) develop within a few weeks after death of the bark. They extrude spores in orange-red tendrils in wet weather. Later, black, pimple-like sexual fruiting bodies (perithecia) originate beneath the bark, which expel white masses of spores during wet weather that collect on the surface of the bark.

Biology

The fungus causing cytospora canker exists in two stages, a sexual stage known as Valsa, and an imperfect, or asexual, stage called Cytospora. The latter is more commonly encountered. The fungus is considered a normal inhabitant of aspen bark microflora, which readily enters and parasitizes bark that has been injured or weakened by any cause. Trunk cankers are formed by a gradual killing of the bark in a more or less circular area over a period of several years. Annual canker growth can be seen by the slight annual callus formation around the perimeter of infection. The fungus fruits readily in the dead outer bark; even when typical canker symptoms fail to develop. The Cytospora stage forms small black fruiting bodies from which sticky spores ooze out in long, coiled, orange-to-dark-red masses called spore tendrils. The“Valsa” stage appears as flask-shaped perithecia formed beneath and in a circle around the old pycnidia. Some ascospores are forcibly discharged from the perithecia; others collect around the openings of the perithecia in sticky white masses on the dead bark. The diseased inner bark remains attached to the tree for 2 or 3 years before turning lighter brown in color and falling off in large pieces.

Effects

Cytospora spp. have a wide geographic and host range, affecting both agricultural and forest tree species. In the Southwest, Cytospora spp. are most common on the hosts listed above and are the most common pathogens found on aspen. Cytospora spp. are weakly parasitic and normally attack stressed trees. Cytospora infection is associated with frost cracks and sunscald, elk feeding wounds, tree vigor, and damage by fire.

Similar Insects and Diseases

The orange tendrils and pimple like bumps associated with sporulation distinguish this fungus from other aspen canker causing fungi (Figure ).

Figure... Orange/red discoloration associated with Cytospora canker (left). Pimples and orange tendril like fruiting bodies produced by Cytospora spp.

Scientific Name (s)

Atropellis piniphila (Weir) M.L. Lohman &Cash

Hosts

Southwestern white pine, limber pine and ponderosa pine

Symptoms/Signs

Cankers appear as elongated depressions covered with bark. Atropellis species produce two kinds of fruit bodies, one flask-shaped and one cup-shaped, on killed bark. The flask-shaped structure develops first. These are black, about 1 mm across, and contain multiple chambers where spores form. The cup-shaped structures are black with a brown interior, measuring 2-4 mm across when moist. They form on cankers 2 or more years old and are present year round. Dark brown mycelium permeates the bark and wood, creating a zone of bluish black stain that in cross-section is initially wedge shaped, pointing toward the center of the stem, becoming irregular with age.

Biology

Infection begins in a branch axil on stems 5-30 years old. There is typically a branch stub in the center of cankers. Some cankers start on internodes, reflecting the ability of the fungus to infect wounds or bruised bark as well as apparently undamaged bark of young stems.

Effects

Atropellis canker can be found throughout the region but its occurrence is infrequent in natural forest settings. Although Atropellis rarely kills trees, there are areas where outbreak levels are reached and mortality occurs in young trees. It can be damaging in Christmas tree plantations where it causes trunk deformities and economic loss.

Similar Insects and Diseases

Atropellis canker may be confused with other canker-causing fungi; however, Atropellis is the only one that stains the wood.

Signs of Atropellis canker include black pimplelike fruiting structures embedded in bark and cup-shaped structures with a chestnut-brown interior that are observable during periods of precipitation.
USDA Forest Service, Southwestern Region
Atropellis piniphila symptoms include black-stained wood.
USDA Forest Service, Rocky Mountain Research Station

Cone Seed Insects

Cone and seed insects, also called conophytes, include a variety of moths, flies, bugs, and beetles. Destruction of forest seeds may be caused by insects that attack the buds, flowers, immature cones, and the seeds themselves. Because flower and seed production by forest trees varies dramatically from year to year and by location, so do impacts caused by cone and seed insects.

In general, cone and seed insects are relatively unimportant under forest conditions as the amount of seed produced by forest trees usually far exceeds the number of seeds destroyed by these insects. However, they can have economic impacts to seed orchards in which seed production is limited.

They can also impact natural regeneration of white pines that are being severely impacted by white pine blister rust. The most injurious groups of cone and seed insects in the Southwest are the seed moths and coneworms (Lepidoptera), seed worms and midges (Diptera), and cone beetles (Coleoptera).

Scientific Name (s)

Conophthorus spp.

Hosts

Pines

Symptoms/Signs

External evidence consists of pitch tubes at the point of entry on the cone stalk or the base of the cone. Following attack, cones turn brown and wither. If beetles have emerged, small round exit holes may be found on the outside of affected cones. Inside, beetles leave cones riddled with tunnels and frass. Adult beetles are reddish brown to black, shiny bark beetles. Larvae are small white, legless grubs.

Biology

One generation is produced per year. Adult beetles bore into the base or stem of immature second-year cones in the spring. A gallery is created along the cone axis, with eggs deposited along its sides. The creation of the gallery severs the conductive tissues of the cone, killing it. Larvae hatch and feed on the scales, seeds, and tissues of the cone. The brood complete development during the summer within the cone, and usually overwinter there. Some new adults emerge and may bore into shoots or conelets and overwinter.

Effects

These beetles cause the death of second-year cones. The amount of mortality is highly variable but in some years a large proportion of cones may be attacked.

Similar Insects and Diseases

This insect is best distinguished from other insects that attack developing cones by the presence of the pitch tube on the cone base or stem.

Life cycle of cone beetles.
Michael R. Wagner (Northern Arizona University)
Damage to interior ponderosa pine cone caused by larva (arrow) of cone beetles.
Michael R. Wagner (Northern Arizona University)
Adult boring hole indicating attack on ponderosa pine cone by Conophthorus cone beetles.
Michael R. Wagner (Northern Arizona University)

Scientific Name (s)

Dioryctria auranticella (Groté)

Host

Ponderosa pine

Symptoms/Signs

Entire cones are usually killed by pine coneworms; partially killed cones become distorted and do not open. Larval feeding cavities inside cones are filled with frass and webbing.

Biology

Larvae begin feeding in ponderosa pine cones in late spring. They make an entry hole in the basal portion of the cone and consume seeds and scale tissues. Mature larvae pupate in the cavities in the cones created by feeding activity of the larvae. Adults emerge in middle to late summer.

Effects

This obligate seed and cone insect can be destructive when populations are high. Up to 80 percent of cones can be damaged per year in the Southwest. Coneworms feed on seeds and scales from a cavity inside the cone, severely distorting the cone and preventing extraction.

Similar Insects and Diseases

There are a variety of cone and seed feeding insects in the West. Other species of insects that feed in seeds and cones of ponderosa pine in the Southwest include pine seed chalcid (Megastigmus albifrons), ponderosa pine cone beetle (Conophthorus ponderosae), and the ponderosa pine seed moth (Laspeyresia piperana). This conophyte is distinguished by the entry hole in the basal portion of the cone and larval feeding cavities filled with frass and webbing.

Damage to ponderosa pine cone caused by larva of the pine coneworm.
Michael R. Wagner (Northern Arizona University)

Scientific Name (s)

Cydia piperana (Kearfott)

Host

Ponderosa pine

Symptoms/Signs

There is no external evidence of infestation. Inside the cones, frass and mining can be seen in the cone axis. Seed pairs on the same scales can become fused together by the silk lined tunnels produced by the larvae. Often these seeds tend to stick to the scales and remain in the cones.

Adult moths have a wingspan of 10 to 20 mm. The fore wings are metallic gray with silver bands. Larvae are 10 to 15 mm when mature, white to cream colored, with a mottled head capsule.

Biology

One generation is produced annually. Eggs are laid at the base of cone scales, on the surface of the scale, or on the cone stalk. Newly hatched larvae bore between the cone scales, enter a seed, consume it, and leave it filled with frass. It then moves on to another seed leaving a silk lined trail. As the larva matures, it burrows into the cone axis and overwinters. In spring, the insect pupates. Following pupation, the adult emerges.

Effects

In some years this insect can consume a large proportion of the seed crop.

Similar Insects and Diseases

A number of insects affect cones. This insect is distinguished by the presence of the frass packed seeds, larvae or mining in the cone axis.

Damage of ponderosa pine seed by ponderosa pine seedworm.
Michael R. Wagner (Northern Arizona University)
Larvae of ponderosa pine seedworm.
Michael R. Wagner (Northern Arizona University)

Scientific Name (s)

Megastigmus albifrons (Walker)

Host

Ponderosa pine

Symptoms/Signs

Adults are antlike in appearance and range in color from yellow to black or brown. Females have a long, curved ovipositor. The larvae are small, white and legless. The outer seedcoat develops normally and shows no evidence of an oviposited egg. When adults emerge they leave a small round hole in the seedcoat.

Biology

Adult emergence lasts for about a month in spring. Females may mate or reproduce parthenogenetically. Eggs are oviposited through the young scales of developing cones directly into the seed. Usually one egg is laid per seed. The larva matures in the seed, consuming its entire contents. The insect overwinters in the seed and pupates in early spring. Some adults emerge at this time while others may diapause for up to 3 years.

Effects

Pine seed chalcid can cause a large percentage of cull seed in commercial seed production operations. Since it is very difficult to distinguish between healthy and inhabited seed, insects are unknowingly transported.

Similar Insects and Diseases

There are a variety of cone and seed feeding insects in the West. Larvae of the family Cecidomyiidae (Diptera) may cause similar reductions in seed production; however, the larvae are not voracious feeders and damage to cones and conelets results from gall formation on the seed scale which prevents seed dispersal. Other species of insects that feed in seeds and cones of ponderosa pine in the Southwest include ponderosa pine cone beetle (Conophthorus ponderosae), pine coneworm (Dioryctria auranticella), and the ponderosa pine seed moth (Laspeyresia piperana )

Larva and seed damage caused by the pine seed chalcid.
Michael R. Wagner (Northern Arizona University)

Insects of Wood Products

A variety of insects attack trees that are recently dead or dying. Losses from these insects are about 1 to 5 percent of the annual timber harvested. Some of these insects have previously been discussed (e.g., woodborers and ambrosia beetles) and others are described on the following pages.

Insects of wood products can either attack moist or dry seasoned wood. Those that attack moist, seasoned wood are usually symbiotically associated with protozoa, fungi, and bacteria that aid the insects in the digestion of cellulose and lignin. Some of these insects will continue to develop in the wood for several years after the wood has been dried and manufactured.

Some of these insects do not obtain their food from the wood. They tunnel into the wood to secure a sheltered base for foraging expeditions and a nursery for the young. Those insects attacking dry, seasoned wood also live in a symbiotic relationship with other microorganisms. These insects can breed successfully in wood with water content as low as 6 percent.

Scientific Name (s)

Camponotus spp.

Hosts

Douglas-fir, pine and true fir

Symptoms/Signs

Carpenter ants are large in size, about 5-15 mm long, and black or black and red in color. They tunnel in the wood of stumps, logs, dead standing trees, the interior dead sections of livings trees, and the wooden portions of buildings. These galleries are honeycomb-like in appearance; the walls are sandpaper smooth, free of frass, and run across the grain. The wood borings, which are coarse and fibrous, are pushed out of the tunnels and may accumulate at the base of inhabited trees.

Biology

Mating occurs during mass flights in the spring. The female then lays eggs, which take approximately 2 months to become mature larvae. The larvae then pupate in cells. Each individual will emerge as one of three possible castes:winged males, winged females, or workers. Carpenter ants do not eat wood but excavate galleries for nesting purposes. These insects are general feeders, and will eat animal food (such as caterpillars, meat, or refuse) and sweets (from aphid honeydew, ripe fruit, or sap.)

Effects

The excavations in wood can be so extensive that the structural integrity of the tree is lost, predisposing the tree to wind breakage.

Similar Insects and Diseases

Horntails or“woodwasps” (Siricidae) have similar excavations in host trees. The main differences being that they actually have the wood borings pass through the digestive tract and are packed in the tunnel behind the larva. They usually attack fresh logs or newly dead trees. Adults are generally thick-waist, wasp-like insects that are metallic blue or black in color. Adults emerge in late spring or summer and lay eggs in solid wood (conifers or hardwoods) and the life cycle can range from 1 to 2 years. Pupal cells are found in the phloem and the exit holes from mature adults are round.

Cross section of stump with carpenter ant galleries.
USDA Forest Service, Southwestern Region
Boring at base of ponderosa pine caused by carpenter ants.
Edward Holsten, USDA Forest Service

Scientific Name (s)

Isoptera Order

Hosts

Most tree species

Symptoms/Signs

Termite damage is honeycomb in shape and follows the grain of wood. There are three types:

Drywood termites . Coarse sand-like fecal pellets found outside of finished wood.
Dampwood termites . Typically colonize dead and down trees and untreated wood in contact with the ground.
Subterranean termites . Presence of mud shelter tubes on wood, walls and tree trunks.

Biology

Termites are eusocial insects that have well developed caste systems. Caste consists of primary reproductives, supplementary reproductives, workers, and soldiers. Only the reproductives have wings and they form large flight swarms outside the colony. As their name implies, workers perform most of the work for the colony. They are generally pale in color, lack compound eyes, and have small mandibles. Soldiers are sterile adults with greatly enlarged and armored heads and mandibles. Their sole duty is defense of the colony against invaders. The conversion of cellulose to smaller units by protozoa and bacterial organisms in the guts of termites allow them to digest cellulose from wood and other plants.

Effects

Termites can be extremely destructive to structures built out of wood. Even houses with a cement block foundation are at risk because subterranean termite tunnels can cross over the cement to wood framing. Damp wood termites attack wood that has high moisture content and do not require contact with the ground.

Similar Insects and Diseases

Termites are sometimes referred to as“white ants”; however they can be differentiated from ants by their soft body, light color, straight beadlike antennae, and broad connection between the thorax and abdomen. Ants are hard bodied, darker in color, elbowed antennae, and have a narrow “waist.”

Damage to sign post caused by termites.
USDA Forest Service, Southwestern Region
Castes (queen, soldier and worker) of termites.
USDA Forest Service, Southwestern Region

Stem Decays and Stains

Decay of wood is caused by fungi that utilize the cell wall components of xylem as a source of nutrition. These fungi have both beneficial and damaging influences on forest stands. In living trees, decay fungi break down tissues in branches, roots, and stems of trees. They play an irreplaceable role in the earth's carbon cycle by returning to the atmosphere billions of tons of carbon each year and provide valuable habitat for many species of wildlife. Although vital to ecosystem functioning, decay can render trees useless for wood products and create hazard trees in recreation sites.

Many decay fungi discussed here decay the heartwood of living trees, others decay the wood of dead trees, and some grow on both live and dead trees. Most decay fungi do not interfere with the normal growth of live trees since they stay in the heart or xylem wood of the host. However, they can affect tree structure and contribute to wind breakage and windthrow as decay progresses. There are some decay fungi that cause mortality. These fungi begin decaying the host as a heart rot and later move into the sapwood and cambium, which cuts off the flow of water and nutrients, girdling the tree. Other fungi decay the wood of dead trees and can also decay dead sections of live trees, such as a dead top or old wound on the bole.

Decay levels in live trees are highly correlated with age. For example, high amounts of decay are typically found in sites where conifer trees are 150+ years old. Susceptibility to stem decay fungi varies with tree species. Some hardwoods—like cottonwood and aspen—are the most susceptible to stem decay in the Southwest, and Douglas-fir, white fir and spruce are in general more susceptible than ponderosa or southwestern white pine. However, susceptibility is also dependent on site quality and host genetics; silviculturists have observed some 70-year-old ponderosa pine sites with high levels of decay.

Scientific Name (s)

Ophiostoma spp., Ceratocystis spp.

Hosts

Conifers

Symptoms/Signs

Blue-green discoloration of sapwood (often in wedge shapes) in recently killed trees. Blue stain fungi frequently originate from bark beetle galleries.

Biology

Blue stain fungi are carried by bark beetles and other wood inhabiting insects and are associated with tree mortality. They are mostly blue-staining and primarily from the genera Ophiostoma and Ceratocystis . The spores germinate and produce a mycelium (thread-like mass) that colonizes the phloem and sapwood, eventually blocking the water-conducting columns of the tree. The formation of a wedge-shaped stain is due to movement of hyphae along the rays from the outside of a log.

Effects

Stain fungi often hasten the death of trees attacked by bark beetles. The stain may result in a reduction in the value of timber or timber products by discoloring sapwood, but does not affect wood strength.

Similar Insects and Diseases

Another group of sapstaining fungi are wind disseminated, of various colors (blue, brown, or gray), and are from the genera Aureobasidium and Alternaria . Black stain fungi, which are closely related to blue stain fungi, also block water-conducting columns. However, black stain fungi spread to healthy trees by root-to-root contact.

Blue stain fungi invade the sapwood and not the inner heartwood.

Scientific Name (s)

Inonotus andersonii (Ellis &Everh.) Cerny

Hosts

Oaks

Symptoms/Signs

Inonotus andersonii produces flat, bright yellow to yellow-brown fruiting bodies with peg-like outgrowths beneath the bark or outermost layers of wood. These fruiting bodies degrade quickly, turning dark dull brown to black, as if the wood was burned.

Biology

Branch stubs are the most common sites of infection, but entry also occurs through trunk injuries. Inonotus andersonii first invades heartwood causing a white rot, and then moves outward, killing the sapwood and cambium (hence the name, canker rot). Trees often break at these cankers.

Effects

It causes mortality when decay advances from the heartwood into the cambium, girdling infected trees.

Similar Insects and Diseases

Old fruiting bodies of I. andersonii are black and are often mistaken for fire scars.

Inonotus andersonii forms fruiting structures that are yellow-orange and grey in color beneath the bark of infected trees (left). Fruiting bodies blacken with age (middle and right).

USDA Forest Service, Southwestern Region

Scientific Name (s)

Phellinus tremulae (Bondartsev) Bondartsez &Borisov

Host

Aspen

Symptoms/Signs

Phellinus tremulae produces woody conks on aspen trunks, typically at branch stubs or scars. The conks are hoof shaped, brown to black, with a rough, cracked upper surface and tan to white pore surface. The conks are usually attached to the host by a granular core of tissue that continues into the decayed branch within the trunk. P. tremulae also produces hard, blackish sterile masses of mycelium (sterile conks) at branch scars, hence the name. The yellowish white spongy decay caused by this fungus is usually confined to a central core.

Biology

Airborne spores of P. tremulae infect fresh branch stubs or wounds. The fungus decays the dead or injured area and then gains entry to the heartwood.

Effects

Phellinus tremulae is the most common cause of aspen stem decay in the Southwest. It causes less mortality than aspen canker fungi or ganoderma root rot but can create hazard trees in recreation sites.

Similar Insects and Diseases

No other fungi with the characteristics of the fruiting body are found in aspen.

Fruiting bodies (conks) of Phellinus tremulae.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Inonotus dryophilus (Berk.) Murrill, Phellinus everhartii (Ellis &Galloway) A. Ames

Hosts

Oaks

Symptoms/Signs

Oaks are host to many heartwood decay fungi. Two of the most common are Inonotus dryophilus and Phellinus everhartii . The former produces an annual fruiting body that degrades quickly following spore dispersal, while the latter produces a perennial fruiting body (conk) that grows a fresh sporulation layer every year.

Biology

As with most decay fungi, branch stubs are the most common sites of heartrot infection, but entry also occurs through trunk injuries. Fruiting bodies develop on living trees.

Effects

Either species can create extensive decay in mature trees, resulting in valuable wildlife habitat and/or creating tree failure risks in developed sites.

Similar Insects and Diseases

There are many other fungi that decay the heartwood of living oak trees, but these are the most common.

Heartrot, Phellinus everhartii, on Gambel oak.
USDA Forest Service, Southwestern Region
Inonotus dryophilus on Emory oak.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Echinodontium tinctorium (Ellis &Everh.) Ellis&Everh.

Hosts

True fir, and occasionally Douglas-fir and spruce

Symptoms/signs

Echinodontium tinctorium produces woody, perennial hoof-shaped conks, 4-20 cm in diameter, usually at the undersides of branch stubs. These fruiting structures sometimes form at wounds or on limbs. The upper surface is dark gray-to-black, rough and cracked. The lower surface is gray-brown to black, composed of thick, blunt, tooth-like spines. The interior tissue is brick red to rust red, from a pigment that extends into the adjacent decayed wood. The common name for E. tinctorium , “Indian paint fungus,” is derived from the Native American’s use of conks in the preparation of red paint pigments.

Biology

The spores of E. tinctorium are dispersed during cool, wet weather in the fall. They remain viable during winter, germinating best after a period of freezing temperatures. The fungus enters branchlets between 0.5 mm to 1.5 mm in size and spreads through the pith to the main branch. Here the fungus can remain in a dormant condition for 20, 50, or even 100 years. When the main branch dies or breaks off, the fungus becomes active again, and decay of the heartwood portion of the main branch begins, eventually spreading to the main stem of the tree.

Effects

This fungus is the main cause of heart rot and volume loss in mature true firs. Conks are reliable indicators of defect and are associated with substantial volumes of decay. One fruiting body usually indicates that the entire cross section of the log is decayed for a distance of 2 m above and 2.5 m below the conk. Decay may also be present in trees that do not bear sporophores. The rot is most common in the mid-trunk but may also extend into the butt or down from the top. In very late stages of decay, the trunk may become completely hollow. Infected trees that break or are windthrown are important sources of hollow logs for wildlife habitat and act as nurse logs for regeneration.

Similar Insects and Diseases

Advanced stages of decay closely resemble equivalent stages of rot associated with Stereum sanguinolentum. However, S. sanguinolentum fruiting bodies are completely different, as they form thin, crust-like layers with a grey to light brown gilled lower surface that turns blood red when bruised.

Indian paint fungus conk showing orange inner tissue.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Cryptoporus volvatus (Peck) Shear

Hosts

Ponderosa pine and other conifers

Symptoms/Signs

Cryptoporus volvatus produces small, cream-colored to tan, leathery fruiting bodies. The most distinguishing feature of C. volvatus is that it has a fungus sheath with a single hole covering the lower spore-bearing surface. This is not a heart-rot fungus, but causes a grayish white rot of the sapwood of recently killed trees.

Biology

Insects enter, feed, and then exit fruiting bodies of the pouch fungus, carrying spores to infect recently killed or dying trees. Typically, it occurs only on dead trees and snags within 1 to 2 years after the tree’s death.

Effects

Most commonly found on ponderosa pine and Douglas-fir in the Southwest, but can infect other conifers. This is not an aggressive pathogen, but invades a tree within the first 2 years of death and is very common in trees killed by bark beetles.

Similar Insects and Diseases

No other conifer pouch fungus has been identified.

Cryptoporus volvatus conks have a covered pore surface with a hole in the bottom where insects enter and exit.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dichomitus squalens (P. Karst.) D. Reid.

Hosts

Ponderosa and piñon pines

Symptoms/Signs

Dichomitus squalens produces a flat fruiting body on the underside of dead branches or stems with intact bark. The pore surface is white when fresh and ages to yellow. The red rot fungus causes a white pocket rot. Like other wood decays, it has two distinct stages:incipient and advanced.

The incipient stage is characterized by a reddish-brown discoloration of the affected wood, unaccompanied by any obvious changes in structure or strength. The advanced stage is characterized by small, often poorly defined, white pockets in the discolored wood, accompanied by progressive changes in structure and reduction in strength. As decay progresses, the pockets become more and more numerous until they merge and give the affected wood the appearance of a fibrous white mass. Eventually, the white lint-like material disappears, leaving the bleached, grayish-brown, decayed wood in either a stringy or a somewhat amorphous condition.

Both stages of red rot are usually visible in a board sawed from a decayed log. At the point where rot started in the trunk heartwood, advanced decay often forms a cavity. Extending in both directions from this point are more or less continuous columns of advanced decay, bordered by incipient decay.

Biology

The spores are dispersed by wind, land in cracked bark crevices of dead branches, and germinate to colonize the area between the bark and wood and eventually the dead wood, provided it has intact bark. The red rot fungus fruits abundantly on the lower side of decaying dead material in close contact with the ground. The flat, white fruiting bodies appear about 4 years after infection and then develop annually during the rainy season for about 6 years.

Effects

Dichomitus squalens is the most common decay of ponderosa pine in the Southwest. It is a decayer of slash (a saprophyte) as well as a heartrot in live trees. It has been reported to cause a significant amount of cull in live trees 150+-years-old when grown for timber. As with other decay fungi, D. squalens provides habitat for cavity nesting birds and other wildlife. Although this fungus is of minor occurrence on living trees in second growth forests, there are reports of extensive decay of young trees (<8lt;80 years) in localized areas.

Similar Insects and Diseases

Many fungi decay ponderosa pine slash, but D. squalens is probably the most common.

Red rot decay affects the heartwood and is typically associated with old growth ponderosa pine.
USDA Forest Service, Southwestern Region
Red rot fruiting body on the underside of a dead ponderosa pine branch.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Fomitopsis pinicola (Sw. :Fr.) P. Karst.

Hosts

Conifers and aspen

Symptoms/Signs

Fomitopsis pinicola forms perennial conks that are corky and shelflike. Its characteristic feature is a red-brown band near the white to cream colored edge. These fruiting bodies form on dead trees and logging slash and not on infected living trees. The decay is a brown cubical rot with shrinkage cracks in which prominent white sheets of mycelium develop.

Biology

This fungus enters living trees with airborne spores colonizing and infecting through wounds and broken tops. It may be introduced into dying or dead trees by insects, as it has been isolated from Douglas-fir bark beetles captured both in flight and from egg galleries.

Effects

Fomitopsis pinicola is one of the most important brown rot pathogens of old-growth western conifers, but it acts slowly and is not considered a major decay pathogen of second-growth forests. However, it is an important component of the coniferous forest ecosystem because it decays dead trees and logging slash and leaves a lignin-rich residue that is very stable and is a major component of the organic matter on the forest floor and in the upper layers of soil. This residue enhances water holding and cation exchange capacities of soil and is a favorable habitat for the development of ectomycorrhizae and for nitrogen-fixing bacteria.

Similar Insects and Diseases

Brown rot caused by F. pinicola is difficult to distinguish from that caused by Phaeolus schweinitizii, a butt rot of Douglas-fir. Since P. schweinitzii is a root and butt rot pathogen, it is found in the lower 3 meters of the trunk and in the roots, and it fruits from the roots out through the soil of live trees. Fomitopsis pinicola only fruits on dead wood material so is frequently observed on stumps.

Fomitopsis pinicola on dead Douglas-fir.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Porodaedalea pini (Brot.) Murril

Hosts

Spruce, true fir, Douglas-fir, pine

Symptoms/Signs

Porodaedalea pini produces swollen knots where branches were previously shed, irregular bulges with exuding resin, and resin flow from knots. It also produces brown fruiting bodies at branch bases, branch stubs, knots, wounds, and cracks. These fruiting bodies, or conks, are bracket-like with a brownish-black upper surface, concentric furrowed rings and a brown undersurface with spores. Punk knots are common in Douglas-fir, western larch, pines, and some spruces. A punk knot is a mass of tightly packed sterile brown hyphae that extends from a decayed branch stub within the trunk to a local swelling on the surface.

Biology

Decay often begins near the junction of heartwood and sapwood and may extend into sapwood adjacent to wounds. The decay is often confined to the heartwood of mature trees, either in one central column or in several discrete columns that extend from branch stubs.

Effects

Porodaelalea pini is thought to be the most common trunk decay fungus of conifers in North America. Decay columns commonly extend 10 meters or more, rendering entire trunks useless for lumber. Decay is much more extensive in old trees in virgin and unmanaged forests than it is in managed forests where trees are harvested at relatively young ages.

Closeup of red ring rot conk on Douglas-fir.
USDA Forest Service, Southwestern Region
Porodaedalea pini fruiting on Engelman spruce at many old branch stubs.
USDA Forest Service, Southwestern Region

Wood Borers

This group contains insects belonging to several order (Coleoptera, Lepidoptera, and Hymenoptera) that bore into the sapwood and sometimes the heartwood of weakend, fire-scorched, recently felled, or dead hardwood and conifer trees. In addition, they can cause substantial economic losses in the form of degraded wood and volume. Descriptions here include families belonging to the order Coleoptera: longhorned beetles/roundheaded borers (Cerambycidae), metallic wood-boring beetles/flatheaded borers (Buprestidae) and ambrosia beetles (Scolytinae Platypodinae). Wood wasps/horntails (Hymenoptera: Siricidae) and clearwinged moths (*Lepidoptera: Sesiidae) are also common wood borers on pines and aspen in the Southwest, respectively.

Scientific Name (s)

Roundhead borers, Cerambycidae, Flathead borers, Buprestidae

Hosts

Conifers and hardwoods

Symptoms/Signs

Larvae are found under the bark of dead and dying trees. These galleries are usually wider than bark beetle galleries and vary in diameter as the larva grows, in contrast to the egg galleries of bark beetles which have a uniform diameter throughout. Roundheaded borer galleries are packed with a coarse boring material while flatheaded borer galleries are packed with fine boring dust. In many species, larvae complete their development in the wood so tunnels extend into sapwood and sometimes the heartwood. Adults emerge through large emergence holes in the bark.

Adult roundheaded borers are medium to large sized, oblong to cylindrical insects. The antennae are often longer than the body, giving them the name“longhorned beetles.” Larvae are relatively large, particularly when fully developed, white, cylindrically shaped grubs. The heads are slightly larger in diameter than the body.

Adult flatheaded woodborers are medium to large sized, flattened, compact beetles. Larvae have a very distinctive shape. The first body segment behind the head is much broader than the following body segments and has horny plates on the top and bottom.

Effects

These insects primarily attack weakened, dead or dying trees. A few species attack and kill apparently healthy trees, such as the western cedar borer on junipers and Agrilus species on Populus. They often attack trees already infested with bark beetles and sometimes compete with them. Larval mines penetrate both the cambial region as well as the wood, sometimes mining it extensively. They are important in the process of nutrient cycling by assisting in breaking down woody material.

Adult metallic wood borer (flatheaded wood borer). Note that antennae are shorter than the body.
USDA Forest Service, Southwestern Region
Ponderosa pine bark borers (adults of roundheaded borers). Note that antennae are longer than the length of the body.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Trypodendron spp., Platypus spp., Gnathotrichus spp. , Xyleborus spp.

Hosts

True fir, spruce, Douglas-fir, pine, aspen, poplar, and maple

Symptoms/Signs

Entrance holes are small for most species (1.5 mm or less) and are marked by piles of white boring dust. Gallery patterns vary by species, but all tunnels run perpendicular to wood grain. The mines of Platypus species penetrate into the heartwood in contrast with most ambrosia beetles in the Scolytinae that mine only the sapwood.

Effects

Weakened, dying, recently cut or dead trees are attacked. Galleries cause defect in logs. Some species can attack freshly cut lumber before it has been dried. Populations can build up in windthrown and fire-killed trees, bases of trees attacked by bark beetles, logging slash, and logs in storage. These beetles are unique among bark beetles in that larvae feed upon a special type of fungus, known as the ambrosia fungus, which grows in the galleries. Larvae do not feed on wood or phloem as in other bark beetles.

Biology

Insect appearance varies between beetles. Adult Trypodendron, Gnathotrichus , and Xyleborus beetles are all dark colored, cylindrically shaped beetles, about 2 to 4.5 mm long (depending on the species). Larvae are white, legless grubs with brown head capsules. All three genera belong to the subfamily Scolytinae. Platypus on the other hand belongs to the subfamily Platypodinae, which is closely related to the Scolytidae. Adult Platypus are more elongate, cylindrically shaped beetles than scolytids.

Similar Insects and Diseases

May be confused with other bark beetles; however, ambrosia beetles are the only ones that bore straight into the bole producing fine, white boring dust.

Entrance points of adult ambrosia beetle. Holes are stained by blue stain fungi.
R. Ladd Livingston (Idaho Department of Lands)
White boring dust caused by ambrosia beetles tunneling in the wood of a bark beetle-killed pine.
Ronald F. Billings, Texas Forest Service

Scientific Name (s)

Callidium spp. (Marsuel), Trachykele blondeli Atimia spp.

Hosts

Junipers and Arizona cypress

Symptoms/Signs

Exit holes.

Effects

Several roundheaded and flatheaded wood borers are aggressive pests in drought-stressed junipers and cypress. Damage can be extensive before symptoms are apparent. Usually a large portion of the tree or the entire tree dies before the insects’ exit holes are noticed.

Biology

Callidium spp. larvae bore beneath the bark making very wide tracks that distinctively score the outer sapwood much like a router. Older larvae excavate oval tunnels deep in the wood and overwinter. Adults emerge throughout the warm months of the year. There is one generation per year. Adult beetles are rather short-horned for cerambycids and dark blue or black. These roundheaded borers leave an oval or rectangular exit hole.

Atimia spp. are small roundheaded borers about 6.5 mm long and generally have a 1-year life cycle. These longhorned beetles attack thin bark portions of seriously weakened and dead juniper and cypress.

Trachykele blondeli , the western cedar borer, is 11 to 17 mm long and attacks juniper and Arizona cypress. Females lay eggs under bark scales and branches of living trees. Flatheaded larvae bore from the branches into the main bole. They feed primarily in the heartwood for several years. Adults emerge in the spring, leaving oval or rectangular exit holes.

Chrysobothris spp. are flatheaded borers of junipers and Arizona cypress. They are medium-sized beetles about 11.5 mm long. Larvae bore into the bark and outer wood of weakened trees.

Similar Insects and Diseases

See cedar bark beetles

Adult western cedar borer.
Steven Valley, Oregon Department of Agriculture
Larval feeding galleries of a juniper borer.
USDA Forest Service, Southwestern Region

Sap Suckers

Most sap-sucking insects are in the orders Hemiptera (true bugs) and Homoptera (aphids, leaf and plant hoppers, and scales). Most of these insects are small and injure the host in two ways:

directly by sucking the host of part of its food supply and water, producing necrotic spots in host tissue, and
indirectly by introducing plant diseases.

The mouthparts of these insects and mites are formed into beak-like structures that are used to pierce host tissues and suck the sap. Damage by sap-sucking insects is often mistaken as a pathogen induced disease. A few of the sap-sucking insects can kill their hosts outright, but most reduce growth rates and weaken the tree. Trees injured by these insects may succumb to secondary insects or fungal diseases. Signs of sap-sucking insect injury consist of enlarged growths or galls, leaf curling, bleaching, yellowing of foliage, tissue necrosis or bark cracking.

In the Southwest, there are several sap-sucking insects that cause noticeable damage to trees and shrubs, but only a few cause significant damage at the landscape scale. Their impacts are typically more important to shade trees and ornamentals. However, two exotic sapsuckers are causing ecological damage where host trees occur near their southern range limit. A spruce aphid, Elatobium abietinum, has been severely impacting spruce forests and ornamentals in some areas of the Southwest since the 1990s. Most recently, oystershell scale, Lepidosaphes ulmi, is causing severe aspen morality and threatens aspen conservation in Arizona.

Use of a hand lens will help in detection and identification, as these organisms are quite small.

Scientific Name (s)

Aphididae

Hosts

Hardwoods and conifers, particularly ponderosa pine and spruce.

Symptoms/Signs

The best evidence of infestation is the insects themselves or shiny leaves from the honeydew. Honeydew is a clear, sugary, sticky liquid that aphids excrete as they feed. It accumulates on the foliage, twigs, trunk and ground. Honeydew attracts ants, and often the presence of ants on a tree may indicate that aphids are there. It is also a good growth medium for sooty mold, which grow on affected portions of the tree. Aphids are small soft-bodied gregarious insects. Adults may be winged or wingless. Nymphs are wingless. They vary in color by species, but may be nearly colorless to green to black.

Biology

Typically aphids produce several generations per year, most are parthenogenetic. The last generation is usually sexual, and then winter is spent in the egg stage. Different aphids feed on different parts of their hosts, including the foliage, twigs, trunk, and roots. All aphids have piercing mouthparts that they use to feed on sap from their host plants.

Effects

Feeding can result in formation of small necrotic spots. Heavy feeding by some species can cause early leaf drop, yellowing of foliage, and reduced growth. In general, these insects are not considered economically important in forest situations. In urban areas, the honeydew can accumulate on walkways and vehicles and attract the attention of the public.

Similar Insects and Diseases

Damage caused by aphids may resemble that caused by needle midges, other sucking insects, or needle diseases.

Aphid damage to conifer host.
USDA Forest Service, Southwestern Region
Eggs of aphids on pine needle.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Elatobium abietinum (Walker)

Hosts

Engelmann spruce and Blue spruce

Symptoms/Signs

The spruce aphid is a small green, soft-bodied insect about 1 to 1.5 mm in size. Both winged and wingless forms occur. Spruce aphids feed by inserting their needle-like mouthparts into host foliage and sucking sap from the needles. First symptoms of feeding are yellow patches on the needles. If the population increases, discoloration intensifies and affected needles turn brown and drop prematurely leaving the internal and lower crown bare.

Biology

Like other aphids, the spruce aphid bears live young with females producing females. Nymphs mature within 3 weeks. During favorable years, large colonies develop during the winter and feed during mild periods. Populations reach a low point during the summer and may be very difficult to find. In the fall, aphids may reappear and begin feeding on one-year old or older foliage. Greatest population increases generally occur from late winter into early spring in northwestern North America and Europe, however, the highest population densities in the Southwestern United States occur in the fall.

Effects

Since populations decline prior to the needle flush in late spring and early summer, the new foliage is unaffected by the overwintering population of aphids. Current year’s foliage is not affected until aphids begin building up again in the fall. Defoliation is usually partial, but in some outbreaks trees are completely defoliated. Severe defoliation can result in tree mortality, especially if trees are also infected with dwarf mistletoe. All age classes of spruce can be infested. Outbreaks are sporadic, were previously short-lived, and associated with dry winter and spring conditions. Ecological damage is most severe in the Southwestern United States.

Similar Insects and Diseases

Needle casts may cause similar damage, leaving the inner and lower crown sparse.

Adult spruce aphid.
USDA Forest Service, Southwestern Region
Closeup of defoliation caused by spruce aphid.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Adelges cooleyi (Gillette)

Hosts

Spruce and Douglas-fir

Symptoms/Signs

Cone-like galls, 12-75 mm long, are formed on spruce branch tips as a result of feeding by the nymph stage of this insect. In late spring, galls are light green to purplish in color and the nymphs may be found inside. In late summer and fall, galls dry up and open and the nymphs emerge, flying to Douglas-fir to complete the next phase of their life cycle. The galls may persist on the branches for several years.

On Douglas-fir the insect feeds on the sap of new needles, new shoots, and developing cones. Nymphs are oval and black with a white waxy fringe. Adults are dark brown and covered with white, wooly wax. Feeding on Douglas-fir does not cause galls to form but rather yellowing and twisting of the needles.

Biology

The entire life cycle requires 2 years. There are six stages in addition to the eggs and crawlers when both host trees are present.

Effects

This insect has a very complex life cycle involving two hosts, spruce and Douglas-fir. On spruce, galls are unimportant in forest situations. However in nurseries, plantations, and on ornamentals, galls are a concern since they kill branch tips and can stunt and deform trees.

On Douglas-fir, infested needles turn yellow and become twisted. Heavy infestations on poor sites result in defoliation.

Similar Insects and Diseases

Damage on Douglas-fir is similar to that caused by needle midges or needle cast.

Waxy filaments ("cotton") created by Cooley spruce gall adelgid on Douglas-fir branch.
USDA Forest Service, Southwestern Region
Cross section of gall showing nymphs of spruce gall adelgid on spruce.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Pinyonia edulicola (Gangé)

Host

Piñon

Symptoms/Signs

Presence of spindle-like swellings at the base of needles that are about 1 cm long with tiny, orange maggots inside.

Biology

Adults lay eggs on needles in late June and early July. Larvae hatch soon afterward and mine into the current year’s needles near the base. The plant forms a gall around the feeding larvae. Each gall contains 5 to 40 small, orange legless maggots. The larvae overwinter in the galls and pupate in the spring.

Effects

This is a common forest insect that rarely causes serious damage. However, heavy infestations in urban settings cause serious defoliation when needles drop prematurely.

Orange-colored maggots of pinyon spindle gall midge.
USDA Forest Service, Southwestern Region
Gall on piñon caused by pinyon spindle gall midge.

Scientific Name (s)

Chionaspis pinifoliae (Fitch)

Hosts

Most pines, spruce, Douglas-fir

Symptoms/Signs

Damage is especially noticeable on ornamental pine and spruce trees growing along dusty roads. Insects feed by sucking sap from needles, causing the needles to yellow and eventually drop.

Biology

The pine needle scale has two generations per year. The 3.5 mm long mature female scales are most conspicuous. They are almost pure white, slender at the front with a wider rear end. Males are smaller and slender and rarely seen. Twenty to 30 eggs are laid in the fall and winter beneath the dead female scale. Eggs hatch in May and the nymphs, or“crawlers”, move to new green needles to feed. Nymphs mature by early July, adults mate, and new clusters of eggs are laid. Scales of this second generation mature by fall and lay the overwintering eggs.

Effects

Heavy infestations over several years can kill young trees and severely weaken larger trees, predisposing them to attack by other pests.

Similar Insects and Diseases

Damage may be similar to that caused by other agents that discolor needles such as black pineleaf scale, pine needle casts, winter desiccation, drought, and aphids. If scales are present, diagnosis is assured.

Ponderosa pine branch with pine needle scale.
USDA Forest Service, Southwestern Region
Closeup of pine needle scale.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Matsucoccus acalyptus (Herbert)

Host

Piñon

Symptoms/Signs

Pinyon needle scale is most easily recognized by finding cotton looking egg masses in spring, black bean-shaped nymphs in fall, or emerged adults in April.

Biology

Adults emerge during middle to late April. Adult females are wingless and flightless and males are winged. After mating, females lay clusters of yellow eggs covered with white, cottony webbing around the root collar, undersides of branches, branch crotches, or crevices in rough bark. Sometimes egg masses are found several meters away from piñon trees on a rock or log. Crawlers emerge about 5-6 weeks after eggs are laid. They climb to the ends of branches and settle on the previous year’s new growth. After inserting their piercing sucking mouthparts into a needle, they become immobile. The body becomes covered with wax and turns black in color. This occurs in the Southwest by early June. By October, the larva resembles a small black bean 1.5 mm long. They overwinter in this stage.

Effects

Infestations can cause needles to yellow and drop. Repeated attacks cause reduced new growth and stunted needles. In severe outbreaks, small trees may be killed outright and larger trees can be predisposed to attack by bark beetles.

Similar Insects and Diseases

Symptoms of needle scale may look similar to needle cast caused by fungi, but fruiting bodies will be embedded in needles rather than external.

Damaged piñon caused by pinyon needle scale.
USDA Forest Service, Southwestern Region
Crawler stage of pinyon needle scale.

Scientific Name (s)

Matsucoccus vexillorum (Morrison)

Host

Ponderosa pine

Symptoms/Signs

The most noticeable symptom is the appearance of branch flagging in spring. Upon closer inspection old egg masses can often be found on flagged twigs, often at branch nodes.

Biology

In April and May, flightless but mobile females and winged males emerge from overwintering pre-adults. Following mating, eggs are laid, often at branch nodes. Eggs are laid in groups, covered with a fluffy white wax, which makes them look like tiny cotton balls. During May and June first stage larvae, called crawlers, settle in temporary feeding spots. The second stage larvae settle in permanent feeding locations in July and August. They feed beneath scales at the base of needles and in cracks and crevices of twigs, particularly around the first and second nodes. During fall the third or pre-adult stage develops and then overwinters. The life cycle is completed in 1 year.

Affected twigs exhibit lesions, brownish areas in the phloem. A fungus, Cenangium spp., is sometimes associated with the lesions. Apparently the principal factor in natural control is branch dieback. Few natural enemies have been found outside of a species of ladybird beetle and a green lacewing.

Effects

Branch flagging is the most common symptom. It occurs primarily in younger trees, less than 75 years old and is most conspicuous in dense stands. Both lateral and terminal shoots can be affected. Mortality rates averaged 1-2 percent in past outbreaks.

Similar Insects and Diseases

Bark beetles known as twig beetles also cause twig dieback in ponderosa pine. However upon close inspection one can find the galleries of these insects either in the inner bark or the pith of affected branches.

Seasonal life history of Prescott scale.
USDA Forest Service files
Waxy filaments ("cotton") created by Prescott scale in Arizona.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Cecidomyia piniinopis (Osten Sacken)

Host

Ponderosa pine

Symptoms/Signs

The first signs of injury are noticeable in early summer when the new shoots start to droop, the foliage turns yellow and the shoot dies. Larvae are red in color and feed in pits under the bark of the current year’s shoots, causing twig deformities. Adult midges are small delicate flies, which resemble mosquitoes. They possess long antennae that are beaded in appearance along with a much reduced wing venation.

Biology

The gouty pitch midge has one generation per year. Larvae overwinter in pits under the bark. In the spring, they make their way to the surface where they spin cocoons on needles.

Effects

Although yellowing and shoot death can be significant, these effects are not considered to be commercially important in most situations.

Closeup of gouty pitch midge damage.
Michael R. Wagner (Northern Arizona University)

Scientific Name (s)

Oligonychus spp.

Hosts

Conifers and hardwoods

Symptoms/Signs

Spider mites suck plant juices with needle like mouthparts, which cause spotting, yellowing, fading, and premature drop of foliage. When populations are heavy, cast skins, webbed foliage, eggs, and other mite activity can be found. Adult spider mites are tiny greenish to reddish colored arachnids with black heads.

Biology

There can be several generations per year. Spider mites have five stages and all but the egg stage bear legs.

Effects

Spider mites are mainly an ornamental tree problem and often go unnoticed in forested situations. Outbreaks of spider mites generally last 1 year and are kept under control by natural enemies, such as predatory mites.

Similar Insects and Diseases

Aphid feeding can have the same symptoms of yellowing, spotting or fading foliage. Adult aphids have winged and wingless individuals. In general, aphids are larger in size and have three pairs of legs instead of four.

Leaf injury from compounds such as ozone may have similar symptoms such as yellowing, spotting, or fading.

Damage to juniper caused by spider mites.
USDA Forest Service, Southwestern Region
Adult spider mites.

Scientific Name (s)

Lepidosaphes ulmi (Linnaeus)

Hosts

Aspen, willow, ash, and woody hosts with thin bark including several riparian andunderstory species.

Symptoms/Signs

Mature scales are approximately 1/8-inch long, gray to brown, and resemble an oysters’ shell. Pale yellow crawlers are observed in June and white flocculence may occur with oystershell scale. Outbreaks often go unnoticed until populations are large and encrust the bark of tree trunks and branches leading to dieback or mortality. At a distance, large populations that encrust the bark appear as dark patches on the white bark of aspen.

Biology

Eggs overwinter beneath the dead mother’s shell. A large portion of eggs begin to hatch in late May to early June, but in Arizona egg hatch can continue throughout the summer. The newly emerged crawlers are mobile and disperse by crawling to a new feeding site or are windblown to new hosts. Once they settle and begin to feed, they form an armored shell as they molt and mature. The armored shell protects oystershell scale from the elements, predators, parasites, and contact pesticides. Asexual and sexual reproduction occur in the fall followed by egg laying.

Effects

Tissue necrosis, bark cracking, and stem girdling occur at the feeding site and may increase susceptibility to pathogens. Cytospora fungi and cankers are commonly associated with oystershell scale damage. Severe outbreaks lead to limb, tree, and stand mortality. All age classes are impacted, and young stems die quickly when infested.

Similar Insects and Diseases

Oystershell scale damage may be mistaken with damage caused by pathogens, mainly cankers of aspen such as cytospora, sooty bark and hypoxylon. The poplar or willow scale also occurs on aspen but is circular and white-yellow, and thus very different from oystershell scale.

White cottony flocculence associated with oystershell scale life stages.
Close up of mature oystershell scales and pale-yellow crawlers on a young aspen stem.
Dark patches of severe oystershell scale infestations on aspen stems and associated crown dieback in a group of aspen.

Scientific Name (s)

Aphrophora spp., Clastoptera spp.

Hosts

Oak, juniper, pines, and southwestern dwarf mistletoe

Symptoms/Signs

The most conspicuous evidence of infestation is the spittle-like froth that surrounds the feeding nymphs.

Biology

Adults usually lay eggs just under the bark of twigs in summer. Eggs overwinter and hatch in spring. Nymphs feed on twigs and leaves and cover themselves with spittle. The spittle protects nymphs from drying and discourages natural enemies. Nymphs migrate to foliage in July and August where they transform to adults. Nymphs and adults feed on the sap of their hosts via their piercing mouthparts. The main natural controls include hot, dry weather that can desiccate the nymphs and a variety of natural enemies including wasp and fly parasites, ants, spiders and birds.

Effects

When these insects are abundant, their feeding can cause discoloration and sometimes mortality of infested twigs.

Similar Insects and Diseases

The juniper twig girdler, Styloxus bicolor, causes twig dieback and flagging on junipers, but may be distinguished from spittlebugs by looking closely at affected twigs. The twig girdler bores inside the twigs, leaving them hollow inside.

"Spit" caused by spittlebug nymphs feeding on pine.
USDA Forest Service, Southwestern Region

Rust Diseases of Conifers

There are several species of stem rust fungi on conifers in the Southwest. The rust fungi are unique in many respects. Some species of rust fungi are autoecious, which means they complete their life cycle on one host. Other species are heteroecious, which means they complete their life cycles on two entirely unrelated hosts. The most important rust species of trees are those that invade the main stem and cause mortality. The most destructive stem rust listed below is white pine blister rust, a nonnative pathogen found in New Mexico.

There is one species of cone rust in the Southwest, and it infects Chihuahua pines in the southeast corner of Arizona.

Scientific Name (s)

Cronartium comandrae Peck

Hosts

Ponderosa and Mondel pines (Pinus eldarica), and Comandra pallida is the alternate host.

Symptoms/Signs

Symptoms of disease on pine begin with slight, spindle-shaped swellings that give rise to pustules that soon exude a mass of rust colored spores. On the nonnative Mondel/Eldarica pine, comandra blister rust causes dieback of branches and eventual tree death. On ponderosa pine, its native host, this disease is rare but occasionally girdles seedlings and saplings. On Comandra pallida, the native alternate host, the rust causes pale yellow leaf and stem spots and leaf abscission.

Biology

The aecial stage develops on pine in late spring through early summer and spores disseminate by wind at that time. These spores are responsible for the primary infection of the alternate host, C. pallida . Rain and cool temperatures favor their germination. The next spore stage, the so-called repeating stage, occurs and builds up on Comandra, as long as there is wet weather. The final stages give rise to basidiospores in late summer, which are wind-dispersed to infect pine needles. The fungus grows into the inner bark, forming a canker that eventually girdles the branch or stem.

Effects

Although this disease causes major damage to lodgepole pine and sometimes ponderosa pine in northern Colorado and Wyoming, it is of minor consequence to ponderosa pine in Arizona and New Mexico. However, Comandra blister rust has done considerable damage to plantings of Mondel pine in the Prescott, Sedona and Payson areas of Arizona. Beginning in the late 1970s, Mondel pines were planted widely as a landscape tree throughout these areas, until it was realized that Comandra blister rust impacted their survival. Infected C. pallida are typically observed near infected Mondel pines.

Figure 3. Fruiting bodies of Cronartium comandrae on bole and branches of infected host.

Scientific Name (s)

Cronartium conigenum Hedgc. & N. Hunt

Hosts

Chihuahua pine, with live oaks as alternate hosts.

Symptoms/Signs

This disease produces swollen, deformed cones on Chihuahua pine that, when ripe, are loaded with orange spores beneath a thick papery outer surface. On oak, this disease produces several different spore stages. The type most often observed has the appearance of brown to black wool on the lower leaf surface.

Biology

This fungus produces spores on swollen deformed cones (galls) of Chihuahua pine in July and August, and other spores on the undersides of leaves of Mexican blue, Dunn, Emory, gray, canyon live, netleaf, silverleaf, and Arizona white oaks throughout the summer. Cones become infected during their first year of development, swell into misshapen galls of various sizes, produce no seeds, and do not open. Aecia develop 2 to 3 years after infection. Galls die after aecial production but remain on the trees. Large galls usually kill the branches that bear them.

Effects

During periods of outbreak brought on by favorable weather, cone rust may kill more than 50 percent of the cones on groups of trees. This disease also affects other pine species in Mexico.

Similar Diseases

None

Swollen Chihuahua pine cone infected with Cronartium conigenum and sporulating. An uninfected cone is on the right.
Detlev Vogler, USDA Forest Service, Pacific Southwest Research Station

Scientific Name (s)

Melampsorella caryophyllacearum J. Schröt., Chrysomyxa arctostaphyli Dietel

Hosts

Fir Broom Rust:White and subalpine fir, with chickweeds and alternate hosts.
Spruce Broom Rust:Engelmann and blue spruce, with bearberry and kinnikinnick as alternate hosts.

Symptoms/Signs

Both of these diseases appear very similar on their respective hosts. The yellow to pale green brooms are dense and compact. Stem or branch swellings may also occur near the point of infection.

Biology

Windblown spores produced on an alternate host are needed to start new infections on trees. Once a tree is infected, the fungus stimulates bud formation, leading to broom development. The brooms shed their needles in the winter and grow new ones in the spring.

Effects

Broom rusts can be found throughout much of the Southwest on their respective hosts. They typically occur at low levels, but are abundant in some locations. Infection typically results in deformity, which is most significant on young trees. Stem infections sometimes result in topkill and/or stem breakage.

Similar Diseases

Broom rusts are sometimes mistaken for dwarf mistletoe witches’ brooms. However, the former are more dense and compact and lack mistletoe shoots. Dwarf mistletoes of true firs and spruces have very limited distributions in the Southwest.

Infected needles release spores in mid to late summer.
USDA Forest Service, Southwestern Region
Needles die and drop, leaving the broom devoid of foliage during winter.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Endocronartium harknessii (J.P. Moore) Y. Hiratsuka

Host

Ponderosa pine

Symptoms/Signs

This fungus forms round or pear-shaped galls on the main stem or branches, which emit orange spores. There is a white-spored race in Arizona and New Mexico that sometimes develops elongated galls.

Biology

This disease spreads directly from pine to pine. Infection occurs on a needle-bearing twig. The fungus stimulates the production of xylem, forming galls, which enlarge over the years. Spores appear on the galls in late spring.

Effects

This disease is probably widespread in the region, but at very low levels. Occasionally it has been destructive to seedlings and saplings, following infrequent“wave years” of new infection. Gall rust deforms but seldom kills older trees.

Similar Diseases

Dwarf mistletoe can cause trunk swellings (cankers) that are usually much longer than those produced by western gall rust.

White-spored gall rust displaying spore sacs and swollen branch.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Gymnosporangium spp.

Hosts

Junipers and Arizona cypress

Symptoms/Signs

There are eight species of Gymnosporangium rusts of juniper in the Southwest and one on cypress. Most Southwestern Gymnosporangium rusts alternate on members of the Rosaceae family (especially serviceberry and hawthorn). The very showy G. speciosum alternates on littleleaf and false mock orange, members of the Hydrangeaceae. On the evergreen host tree, these rusts cause witches’ brooms, galls, other branch distortions, and dieback of twigs and branches. Brown to orange hornlike or cushionlike projections (telia) are produced in the spring; these swell and gelatinize during wet periods and are quite spectacular. On alternate hosts, the rust develops colorful spots and localized swellings on leaves, fruits, and green twigs, followed by casting or distortion and death.

Biology

Some Gymnosporangium species complete their life cycles in 1 year, but many require 2 years. Two spore stages form in spring through late summer on the alternate host. The second spore type is wind disseminated and infects juniper or cypress (depending on the rust species). Gymnosporangium species overwinter in their evergreen hosts, where they produce telia in the spring. The telia produce the final spore stage that infects the alternate host. Many of these rust species become perennial in juniper or cypress and produce telia annually on galls, swellings, or witches’ brooms, until the infected area is killed by the infection.

Effects

In the Southwest, these fungi generally cause minimal damage to junipers, other than some deformities. Impact on the foliage and fruits of the alternate hosts may be more significant in years with adequate rainfall, causing early defoliation.

Similar Diseases

Witches’ brooms caused by some of the juniper rusts could be confused with mistletoe infection.

Telia stage of Gymnosporangium calvariiforme on common juniper.
USDA Forest Service, Southwestern Region
Telia stage of Gymnosporangium speciosum on unidentified juniper.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Cronartium arizonicum Cummins

Host

Ponderosa pine, with Indian paintbush as the alternate host.

Symptoms/Signs

Dead and dying branches, often in the middle of the crown, are quite characteristic of this disease. Spore-producing sacs (aecia) are produced on live infected branches, and erupt through the bark in spring to midsummer. Trunks are not affected by this disease even though the fungus travels through it to get to the branches.

Biology

Initial infection occurs on a needle-bearing twig. The fungus grows into the sapwood and eventually reaches the main stem. It grows up and down the stem, entering and killing individual branches. Disease from this pathogen results in a progressive invasion and killing of branches by the fungal mycelium that is perennial in the trunk, but does not injure it. From an initially infected branch, the parasite grows into the wood of the trunk and advances upward and downward up to 18-21 cm per year in each direction and then out into branches where it sporulates. Infected branches typically die the following year.

There are at least three varieties of limb rust in the western U.S., collectively known as Peridermium filamentosum. Cronartium arizonicum, which uses Indian paintbrush (Castilleja spp.) as an alternate host, is the most common variety in Arizona and New Mexico. Another variety that spreads directly from pine to pine has been detected on the Kaibab Plateau in northern Arizona.

Effects

Although the disease can be very damaging to individual trees, its occurrence in an area is usually low. In Arizona, it has been observed throughout the ponderosa pine type, from the Coronado National Forest to the North Kaibab Ranger District.

Similar Diseases

Many agents can cause branch mortality, but limb rust is distinctive because of the progressive mortality in the center of the crown.

Limb rust infection typically starts mid-crown and spreads in both directions.
USDA Forest Service, Southwestern Region
Live limbs bearing Cronartium arizonicum spore sacs in the spring/summer die in the fall.
Thomas E. Hinds (USDA Forest Service, Rocky Mountain Research Station)

Scientific Name (s)

Cronartium ribicola J.C. Fisch.

Hosts

Southwestern white pine is the only species currently affected in the Southwest; limber pine and bristlecone pine are also susceptible. Currants and gooseberries (Ribes spp.) are alternate hosts.

Symptoms/Signs

Tapered branch swellings or stem swellings (on young trees) are an early symptom on pine. The characteristic white blisters (aecia) appear on mature cankers in late spring. After the blisters disintegrate, cankers have a dark, roughened appearance. Flagging (i.e. recently killed branches with red needles) occurs several years after initial infection.

Biology

Spores produced on Ribes leaves are wind dispersed and infect pine needles. The fungus grows into the inner bark, forming a canker that eventually girdles the branch or stem. Blisters erupt through the bark of the canker, releasing the spores that infect Ribes.

Effects

This nonnative disease is one of the most damaging tree diseases in North America. Trees of all sizes can be affected, although smaller trees are killed more rapidly than larger trees.

In the Southwest, white pine blister rust was first observed in 1990 near Cloudcroft, New Mexico. It was dispersed throughout the Sacramento and adjoining Sierra Blanca but was more common in moist, mixed conifer sites above 2,450 m. The disease was later found in the nearby Capitan Mountains and on Gallinas Peak (near Corona, NM). By 2005, it was discovered on the Gila National Forest in far western New Mexico. Although the forests of Arizona were scouted since the Cloudcroft discovery, the first confirmed observation was in 2009, in the east-central White Mountains, including both White Mountain Apache tribal lands and the Apache-Sitgreaves National Forests.

Blister rust incidence does vary by habitat, with the higher incidence found on cooler, wetter sites. However, there is also a temporal effect. In newly infested areas, branch flagging and death of small trees is observed with little, if any, impact to mature trees. In older infestations, branch flagging and top kill of mature trees is common.

Similar Diseases

The slight swelling and roughened bark formed by Atropellis canker can be mistaken for blister rust, and so can branch flagging due to rodent feeding of dwarf mistletoe infected limbs. Ribes leaves are often infected by other rusts, such as Coleosporium ribicola, that can be mistaken for white pine blister rust.

Top-kill and flagging on mature white pine.
USDA Forest Service, Southwestern Region
White pine blister rust sporulating on the bole of an infected tree.
USDA Forest Service, Southwestern Region

Hardwood Leaf Diseases

Hardwood leaf diseases in Arizona and New Mexico are most often observed on aspen, Arizona sycamore, cottonwood and willow. Although clonal susceptibility to foliage pathogens is common for aspen and willow, whole areas can become infected during favorable moisture periods. Severe infection can cause premature defoliation and reduced tree growth.

Scientific Name (s)

Drepanopeziza populi (Lib.) Rossman &W.C. Allen

Hosts

Aspen and cottonwood

Symptoms/signs

Black leaf spot is common on aspen and cottonwood. Small brownish spots appear on infected leaves in late July and early August. The spots later enlarge and turn blackish, are of various sizes and irregular in outline, and have a yellowish to golden border. Infected leaves fall prematurely.

Biology

Primary infection occurs soon after leaves emerge in spring, from spores produced on twig lesions or from infected fallen leaves. Additional spores are produced on newly infected leaves, which initiates the repeating cycle of disease that continues with wet weather until leaves fall. Symptoms intensify and seem to ascend trees as the season advances. Drepanopeziza populi survives the winter as tiny stromata in fallen leaves and twig lesions.

Effects

Severe outbreaks may cause foliar browning in midsummer and nearly complete defoliation by late August. Regrowth follows in late summer and early autumn, and twig dieback may follow in winter because late season shoots lack normal cold hardiness. Defoliated trees produce less wood for 1 or more years following an outbreak.

Similar Insects and Diseases

Several agents can cause premature defoliation of aspen including aspen tortrix, western tent caterpillar, melampsora rust, frost, and drought . The irregular brown to black blotches on leaves distinguish black leaf spot from the other agents.

Black leaf spot of aspen caused by Drepanopeziza populi.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Ciborinia whetzelii (Seaver) Seaver

Hosts

Aspen and cottonwood

Symptoms/signs

Ciborinia whetzelii forms brown to black spots, or stromata, in blighted leaves. Infected leaves turn brown and the ink spots, or sclerotia, begin to drop out leaving a circular hole in the dead leaves.

Biology

Ciborinia whetzelii infects young leaves in the spring by ascospores produced on fruiting structures that overwintered on fallen leaves. Infected leaves begin to die midsummer, but defoliation may not take place until autumn.

Effects

Ink spot leaf blight is more severe on smaller aspen trees and in the lower crowns of larger trees. As with many aspen diseases, some clones appear to be more susceptible than others.

Similar Insects and Diseases

This fungus may be confused with Drepanopeziza populi; however, C. whetzelii produces well-defined circular and slightly raised fruiting structures, while those of D. populi are irregularly shaped and flattened.

Black ink spots (sclerotia) on aspen leaf.
Thomas E. Hinds (USDA Forest Service, Rocky Mountain Research Station)

Scientific Name (s)

Melampsora spp.

Hosts

Aspen, Douglas-fir, willow, and cottonwood

Symptoms/signs

Several Melampsora species occur in the region. Melampsora medusae causes conifer-aspen leaf rust; M. occidentalis causes conifer-cottonwood rust; and M. epitea , which causes willow rust. Powdery yellow to yellow-orange spores produced on both sides of leaves or needles.

Biology

The life cycle of many rust fungi are very complex. In the early spring, infected dead aspen leaves on the ground release basidiospores that can only infect Douglas-fir. A different spore produced on Douglas-fir is wind disseminated and infects aspen leaves in the summer. Yet another spore, the golden-yellow uridiniospore, appears on both sides of infected aspen leaves within 2 weeks. This is called the repeating stage because these spores germinate to reinfect aspen leaves throughout the growing season. An overwintering spore is produced on the underside of infected leaves in late fall.

Effects

During wet summers this fungus can cause the leaves of highly susceptible clones to shrivel and drop prematurely, reducing growth.

Similar Insects and Diseases

The orange spores are distinct to Melampsora rust on the listed hosts.

Rust pustules of Melampsora spp. on aspen leaves.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Venturia tremulae var., grandidentatae M. Morelet

Host

Aspen

Symptoms/signs

Curling, blackening and dieback of the tips of terminal and lateral shoots on young aspen sprouts.

Biology

Primary infections by Venturia tremulae var grandidentatae occur in spring on leaf blades, petioles, and young stem tissue. Dark brown to black lesions expand rapidly, causing leaves and shoots to droop, whither, and become brittle. Secondary infections, promoted by wet weather, are initiated throughout the period of shoot elongation by conidia from newly blighted shoots. New shoots frequently grow adjacent to blighted ones and are blighted in turn. Lesions do not extend into woody twigs.

Effects

In wet seasons, shepherd's crook can kill virtually all terminal shoots in young susceptible aspen within the same locale. This damage reduces height growth and deforms trees by causing a bend in the stem at the point where a lateral shoot became a new leader following death of the terminal shoot. Successive leaders may be killed during wet favorable summers. Plants less than 3 meters tall are at greatest risk, and damage becomes negligible as trees attain heights greater than 5 meters.

Similar Insects and Diseases

This is the only fungus on aspen causing black lesions on leaves, petioles and stems, which curl and form characteristic shepherd’s crooks.

Curling and blackening of aspen shoots from Shepherd's crook.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Apiognomonia veneta (Sacc. &Speg.) Höhn.

Hosts

Arizona sycamore

Symptoms/signs

Sycamore anthracnose has a range of symptoms corresponding to the three phases of this disease. The symptoms include:cankers on buds and twigs; shoot blight following a period of cold spring weather; and leaf blight from direct infection of leaves. Foliar lesions characteristically extend along the veins and involve interveinal tissue. Sometimes large irregular marginal lesions develop.

Biology

Apiognomonia veneta enters twigs via petioles during the growing season and remains quiescent until host dormancy, when it colonizes and kills bark and cambium. In the early spring, spores produced in these cankers infect new shoots and leaves. Shoot blight, the second phase of the disease, involves the rapid death of expanding shoots and leaves. This phase tends to develop suddenly during a period of cold spring weather. The third and final phase of sycamore anthracnose is leaf blight, which results from direct infection of leaves. It starts out most severe on low branches, and intensifies and spreads upward during wet seasons, causing premature leaf drop. Leaves are most susceptible during the first few weeks of growth. Hyphae of the fungus often grow down petioles into the twigs, setting the stage for the next year’s damage.

Effects

Repeated twig dieback alters the form of sycamores in two ways. First, when the terminal twig on a branch is killed and a lateral takes over as the new leader. Since infection takes place repeatedly during the life of a susceptible tree, the branch axis changes direction again and again, and crooked branches result. The second altered form is the development of a cluster of twigs around a common point on a branch because of the repeated killing of terminals.

Similar Insects and Diseases

Sycamore anthracnose may occasionally be confused with injury by late spring frost . However, frost damage may affect several species in the same area and Apiognomonia veneta affects only sycamore.

Infected trees refoliate but branch dieback is evident.
USDA Forest Service, Southwestern Region
Severe defoliation by sycamore anthracnose.
USDA Forest Service, Southwestern Region

Conifer Needle Diseases

Although occasional outbreaks appear quite dramatic, long-term damage from conifer needle diseases in the Southwestern Region is usually minor. Sporulation, spread, and infection by these fungi are frequently restricted to a specific season, depending on the pathogen, and successful infection depends on favorable weather conditions. Needle diseases are often more pronounced on younger trees and the lower crowns of large trees, due to more humid conditions favorable to disease fungi.

Scientific Name (s)

Elytroderma deformans (Weir) Darker

Hosts

Ponderosa pine, piñon, limber pine, and southwestern white pine

Symptoms/Signs

Needles begin to fade in the fall of the year of infection, and by late winter are lighter in color than uninfected needles. By spring, the infected needles turn straw color as the tree breaks bud. The fruiting bodies are elongated (average 10 mm in length) and black when visible on dead needles. Distinctive“witches’ brooms” are formed by the sprouting of epicormic buds. Resin cysts can be found in infected twigs.

Biology

Spores initially infect new needles through the epidermis following bud break, but infection can continue into the fall until temperatures are too low for spore germination and growth. There are two types of spores:one spore is spread by water and the other is spread by wind. Discharge of spores occurs during and after a rainstorm, when new needles are probably most susceptible to infection. The fungus spreads throughout the needles and into twigs before the needles are killed. When twigs become infected, the fungus can perennially infect needles on the same twigs. Conditions conducive to needle infection by spores only have to occur once, after which the disease can progress within the infected tree.

Effects

Although elytroderma needle cast is known as an occasional disease of ponderosa pine in the Southwest, it is common in some areas. In mature trees, if less than one-fourth of the branches are infected there is little or no effect on the tree, but if more branches are infected, needle cast alone can kill a tree or predispose it to attack by bark beetles.

Similar Insects and Diseases

The witches’ brooms produced by elytroderma needle cast are similar to those caused by dwarf mistletoe , however, the existence of dead second year needles are indicative of needle cast and not dwarf mistletoe infection. Elytroderma is the only needle cast that is perennial.

Cambium of infected branch has pockets of dark resin.
USDA Forest Service, Southwestern Region
Witches' broom formed from Elytroderma infection.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Lophodermella cerina (Darker) Darker

Host

Ponderosa pine

Symptoms/Signs

Lophodermella cerina infects the needles of seedlings, saplings, and the lower crown of larger trees. Current year needles become infected and turn brown and die by early summer of the following year. After the next bud break, green current year needles and brown 1-year needles give the tree a distinctive appearance. The brown needles are“cast” prematurely compared to normal needle drop. Repeated infection occurs only with favorable weather conditions and results in thin crowned trees.

Biology

Fruiting bodies are short, oval, light brown, and easily overlooked. The spores mature after the needles have been cast. They infect new needles shortly after bud break. Spores germinate and infect needles directly through the epidermis. Infected needles extend normally and are usually killed by the fungus before the next year’s needles emerge.

Effects

Although rare, growth loss is the primary long-term effect of needle cast. Successive years of infection are usually the result of repeated abnormally high rainfall in spring and early summer. Though trees can be killed if infection is repeated for several years in a row, they are more often predisposed to other pests.

Similar Insects and Diseases

From a distance, trees with needle cast symptoms may be mistaken for those affected by winter damage deicing salt damage , or needle miners . On close inspection, needle cast needles are completely brown with dark fruiting bodies present. Winter damage, salt damage, and needle miner needles often have brown needle tips with green bases.

Diseased 1-year needles are cast in late summer leaving current year and 2-year+ needles.
USDA Forest Service, Southwestern Region
Lophodermella needle cast on 1-year needles before bud break.
Borys Tkacz (USDA Forest Service, Washington Office)

Scientific Name (s)

Coleosporium jonesii (Peck) Arthur

Hosts

Piñon; Ribes spp. are alternate hosts.

Symptoms/signs

White columnar sacs (aecia) filled with orange spores occur on all surfaces of piñon needles in the spring. On ribes, uredinia appear as small, round, golden yellow pustules during the summer. Telia, which are waxy and darker orange, develop in late summer on the same ribes leaves.

Biology

Piñon needle rust must go through five spore stages on two different hosts to complete its one year life cycle. Spores from ribes leaves infect pine needles in late summer to early fall, where the fungus overwinters. Orange droplets form on infected needles in early spring and bright orange aeciospores by late spring. The latter are wind disseminated and infect newly emerged ribes leaves. Urediniospores develop on the ribes and multiply during wet periods. Telia develop in late summer followed by the final spore stage which infects pine needles.

Effects

Affected needles drop prematurely. This disease is encountered infrequently on piñon, but is very common on Ribes spp.

Similar Diseases

Coleosporium jonesii on ribes can be mistaken for other rusts of ribes, such as white pine blister rust, Cronartium ribicola. There is another needle rust of piñon in the region, Coleosporium crowellii, which is microcyclic, meaning there is no alternate host. The fruiting structures are more reddish-orange and waxy rather than powdery as in Coleosporium jonesii.

Uredinia and telia of Coleosporium jonesii on Ribes cereum, wax current.
USDA Forest Service, Southwestern Region
Aecia of Coleosporium jonesii on piñon.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Dothistroma septosporum (Dorog.) M. Morelet

Hosts

Ponderosa pine and piñon

Symptoms/Signs

Symptoms first appear as yellow or tan bands around the needles, which later turn red. Infection of current and second year needles is usually in the lower crown of sapling size trees. Seedlings and large trees are rarely infected. Newly infected needles have green bands that turn red or brown in late summer. These needles die from the tips back. Infected second and older year needles can be cast the same year they become infected.

Biology

Needles are infected during rainy periods by rain-splashed spores. The number of infection cycles depends on the climate. During wet years, several cycles of infection can occur. The Dothistroma septosporum stage is the asexual, imperfect stage, and the one most commonly found.

Effects

Dothistroma needle blight has been observed on ponderosa, piñon, and Austrian pine in New Mexico. It is most often associated with offsite planting. Several years of severe infection results in reduced growth and death of infected trees.

Similar Insects and Diseases

Infected trees can look like the lower crown was sprayed with herbicides. The death of needles from the tips to fascicle is similar to the affects caused by high concentrations of de-icing salts

Dothistroma blight of Austrian pine.
Robert L. Anderson, USDA Forest Service

Scientific Name (s)

Rhabdocline spp.

Host

Douglas-fir

Symptoms/signs

Tiny chlorotic spots on one or both surfaces of first year and occasionally older needles arise in late summer or early autumn. These lesions enlarge and darken to purplish brown spots and bands that are conspicuous by late autumn to early spring. Numerous lesions coalesce and involve the entire needle except for a short basal portion. Discolored foliage is most conspicuous the following spring.

Biology

Rhabdocline species produce apothecia May through June in needles still attached to the twigs. The apothecia appear as swellings up to several millimeters long and open by splitting the needle surface, usually near the midrib. Ascospores are airborne and penetrate developing needles directly through the cuticle. Only one infection period occurs per year, but it may last several weeks. Needle colonization increases during the fall as symptoms become apparent. Infected needles drop during the winter, making missing foliage the only noticeable sign of disease.

Effects

This is the most important needle disease of Douglas-fir. Damage can be severe in Christmas tree plantations and ornamental nursery stock. Seedlings infected in nurseries can become foci of subsequent damage in plantations. Occasional outbreaks in forest stands can appear spectacular, but trees usually recover.

Similar Insects and Diseases

The fruiting body of Rhabdocline may be confused with secondary fungi.

Needle cast due to Rhabdocline needle cast.
Bob Cain (USDA Forest Service, Rocky Mountain Region)
Rhabdocline needle cast lesions on 1-year Douglas-fir needles.
John Schwant, USDA Forest Service

Scientific Name (s)

Lirula abietis-concoloris (Mayor ex Dearn.) Darker

Host

White fir and subalpine fir

Symptoms/signs

Dark brown or black elongate fruiting bodies are found on second year needles. The fruiting bodies extend down the center of the lower needle surface for almost the full length.

Biology

Infection begins on young, developing needles during periods of rainfall. Fruiting structures mature on these needles the following spring and needles turn brown.

Effects

Lirula abietis-concoloris occurs sporadically and infects only newly emerged needles. Damage is rare since it takes several years of favorable weather for repeated infection to defoliate trees and affect growth and vigor.

Similar Insects and Diseases

None.

Death of 2-year needles caused by true fir needle cast.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Lophodermella arcuata (Darker) Darker

Host

Southwestern white pine

Symptoms/signs

This fungus is identified by the dark brown to concolorous, elongate to elliptical, fruiting structures, which develop on previous year’s dead and dying needles.

Biology

Fruiting bodies in dead, second year needles open by means of a longitudinal fissure during warm wet weather and release colorless spores that have sticky, gelatinous sheaths. Airborne spores settle and penetrate young, developing needles. The following spring, diseased needles turn reddish brown and by July, they are straw colored.

Effects

Lophodermella arcuata infects only the current year’s needles, and a single attack results in only partial defoliation of the host. Repeated consecutive infections are rare, but can lead to reduced tree growth and vigor.

Similar Insects and Diseases

This is the only known needle cast disease of white pine in the Southwest.

Fruiting bodies of Lophodermella arcuata are the same color as the faded needle.
USDA Forest Service, Southwestern Region
Lophodermella arcuata causes browning of 1-year needles, which is most noticeable just before bud break of current year needles.
USDA Forest Service, Southwestern Region

Insect Defoliators

Defoliating insects damage trees by eating leaves or needles, removing the photosynthetic tissue critical for plant maintenance and growth. A significant loss of leaves or needles results in growth loss, increased susceptibility to attack by other insects and pathogens, and sometimes tree mortality.

The impact of defoliation on individual trees is dependent on a variety of factors. Tree species vary in their tolerance to defoliation. In general, hardwood species can sustain repeated defoliation events over several years because they store large food supplies and can refoliate in the same year. The timing of the defoliation relative to seasonal growth phenology is also important. For example, late season defoliation of hardwoods has a lower impact than does late season defoliation of conifers. A single late season defoliation of pines often results in tree mortality. Trees that are healthy and growing vigorously will generally survive defoliation better than stressed trees.

Historically, the two most destructive defoliators in the Southwestern Region were the western spruce budworm and the Douglas-fir tussock moth. Both of these defoliators can cause severe growth loss, top-kill, increase susceptibility to bark beetles, and cause outright tree mortality. Other defoliators are observed, but are not typically as widespread. Beginning in the early 1990s, the exotic spruce aphid and a native Janet's looper caused high levels of mortality in the spruce-fir forest type in the White Mountains and Pinaleño Mountains of Arizona. Two different looper species have been observed in the Sacramento Mountains of southeastern New Mexico in the early 2000s, causing tree mortality in the mixed conifer and subalpine fir types.

Many other defoliating insects that have the potential to cause localized problems are not included in this guide. Consult Federal or State forest health personnel for assistance on insects not described in this guide.

Scientific Name (s)

Choristoneura freemani (Razowski) (C. occidentalis Freeman)

Hosts

Douglas-fir, true firs, and spruce

Symptoms/Signs

Adults are a mottled orange brown and have a wing span of 22 to 28 mm. Eggs are white to light green in color and are laid in shingle-like masses on the underside of needles. Newly hatched larvae are cream colored with brown heads. Full-grown larvae are 25 to 32 mm long with brownish head and body and prominent ivory colored spots. Pupae are 12 to 16 mm long, broad at the head and tapering toward the tail. Signs of feeding include current foliage being partially or fully chewed over the entire tree; expanding buds mined and evidence of feeding on second and third year shoots possible; and shoots webbed into feeding shelters giving the tree a reddish-brown appearance.

Biology

Eggs are laid in July and August and hatch in about 10 days. The initial larvae do not feed, but spin silken shelters (hibernacula) under bark scales or lichens where they will hibernate. The next spring larvae mine old needles until the buds swell and then bore into the buds and feed on the expanding needles. Later they web the growing tips together and feed on the new needles. The larvae pupate in June and July. Adults begin to appear in July and start egg laying for the next generation.

Effects

Defoliation by western spruce budworm can cause growth loss after 1 or 2 years. Repeated heavy defoliation (4 or 5 years) can cause a significant decrease in growth, tree deformity, top-killing, and ultimately tree mortality, particularly in seedlings and saplings.

Similar Insects and Diseases

The white fir needleminer Epinotia meritana , feeds inside the needles of true fir. Mined needles are a bleached yellowish color and do not have a chewed appearance. The mature larvae are much smaller (8mm) than western spruce budworm and yellowish green to cream colored. The adult moths have wings that are dusty gray with alternating bands of dark scales. Wing spread is 11 mm. Repeated defoliation by white fir needleminer can cause branch mortality, deterioration of tree crowns and increased susceptibility to fir engraver.

Near view of western spruce budworm defoliation to Douglas-fir.
USDA Forest Service, Rocky Mountain Region Archives
Adult western spurce budworm with pupal case.
USDA Forest Service, Intermountain Region Archives

Scientific Name (s)

Galenara consimilus (Heinrich)

Hosts

Douglas-fir and white fir

Symptoms/Signs

Larvae feed on the foliage often stripping its host of needles. The immature stages of this insect have not been described. The forewings of the adults are light gray overlain with grayish-brown and brownish-black scales.

Biology

Little is known about the biology of this insect. Outbreaks of this occasional pest occurred in 1924, 1928, 1951, 1958, 1974, 1977, and 2002 in New Mexico, the only state in which this insect is known to occur.

Effects

This insect can cause heavy defoliation of Douglas-fir and white fir resulting in growth loss and top-kill. Several years of heavy defoliation can result in high levels of tree mortality.

Damage of fir caused by New Mexico fir looper.
USDA Forest Service, Southwestern Region
Larva of New Mexico fir looper.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Macrohaltica ambiens (LeConte= Altica ambiens)

Hosts

Alder

Symptoms/Signs

Larvae are skeletonizers, meaning that they feed on the tissue between the veins, but leave the veins intact. Adults chew holes in the leaves. Adult beetles are dark shiny blue, and about 5 mm long. The mature larvae are a little longer and narrower than the adults, brown to black above and yellowish below.

Biology

One generation is reported per year. Adults hibernate during the winter in duff at the base of trees and in other sheltered places. They emerge in early spring to resume feeding. Eggs are laid in clusters on foliage. Larvae hatch and begin feeding within a few days. One source reports that larvae mature in August; but in the Southwest they mature earlier in the season.

Effects

No long-term effects are documented. Outbreaks are generally short lived and sporadic with heavy defoliation. Trees tend to recover quickly.

Similar Insects and Diseases

Although other defoliators feed on alder, outbreaks of these other insects have not been reported.

Defoliation of alder caused by alder flea beetle in Arizona.
USDA Forest Service, Southwestern Region
Adult alder flea beetle.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Nepytia janetae (Rindge)

Hosts

Engelmann spruce, corkbark fir in Arizona; Engelmann spruce, corkbark fir, Douglas-fir, ponderosa pine, and southwestern white pine in New Mexico

Symptoms/Signs

The taxonomic status of this species is uncertain as there is considerable variation in body coloration and host feeding between Arizona and New Mexico. Studies are attempting to determine if there are two separate species or two subspecies. Larvae feed on foliage, chewing needles of all ages. Early instar larvae scrape or score the outer surface of needles, while later instars consume, partially consume, or clip needles. Partially consumed or clipped needles accumulate beneath defoliated trees. Mature caterpillars are approximately 2.5 cm in length. The upper surfaces of larvae are gray with dark brown and green markings in a herringbone pattern and with irregular pale cream lateral stripes. The head capsule is mottled with a distinct black stripe above the mouthparts. Larvae can be seen in the foliage, hanging from silken threads, beneath the tree on ground or snow and climbing up the bole of the tree. Adults are small light gray moths that can be seen flying singly through the woods or flying in large numbers around the tops of host trees. Pale green (Arizona) to mottled brown and cream (New Mexico) colored pupa can be seen on the foliage wrapped in webbing.

Biology

Nepytia janetae has one generation per year. Adults appear in late June, peak flight is reached in early July. Eggs hatch in late September. Larvae feed throughout winter and spring. Soome larvae are present until early July and there can be considerable overlapping of life stages.

Effects

Outbreaks develop rapidly, last 2 to 3 years, and collapse due to starvation, parasites, and disease. During outbreaks, heavy defoliation results in growth loss and, with multiple years of defoliation, tree mortality. Mortality can be due to defoliation alone or due to secondary infestation by bark beetles. This insect caused extensive damage and mortality to spruce and corkbark fir in the White Mountains and Pinaleo Mountains of Arizona in the late 1990s. Associated spruce beetle mortality occurred only in the Pinaleo Mountains. During the mid-2000s, an outbreak also occurred in the mixed conifer forest type of the Sacramento Mountains, New Mexico. All conifer species in the impacted area were defoliated.

Similar Insects and Diseases

See New Mexico fir looper. Another species of looper (Mountain girdle, Enypia grisiata) has caused heavy defoliation to sprucefir in the White Mountains of Arizona. Similar insects in other regions (e.g. western hemlock looper and western false hemlock looper) have not been observed in the Southwest.

Partially consumed white fir needles by Nepytia janetae.
USDA Forest Service, Southwestern Region
Adult Nepytia janetae.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Coletechnites spp.

Hosts

Ponderosa pine and piñon

Symptoms/Signs

Adults of pine-feeding needleminers are small, narrow-winged, mottled, silvery-gray moths with a wingspan of about 10 mm. Eggs are too small, 0.2 mm in diameter, to be noticeable. Larvae are brown, 8 mm long when fully developed, and usually found mining within current year’s needles. The pupae are elongate, cylindrical black, and about 6 mm long. Needles inhabited by third and fourth instar larvae turn a faded yellow-brown in color and have several tiny holes in them for frass disposal and larval exit.

Biology

Adult moths emerge and fly in June and July. Eggs are laid inside previously mined needles. Larvae begin hatching in July, crawl to and mine into previously uninfested needles and overwinter. Pupation occurs in late spring.

Effects

Persistent infestations can cause severe discoloration, defoliation, and reduced growth of stems, shoots, and needles.

Similar Insects and Diseases

Similar symptoms, i.e., discoloration and defoliation, can result from scale insects, aphids, and needle cast diseases. However, only the needleminers leave telltale holes in the mined needles.

Needle damage caused by Coleotechnites feeding on ponderosa pine.
USDA Forest Service, Southwestern Region
Closeup of needle damage caused by Coleotechnites feeding on ponderosa pine.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Coloradia pandora (Blake)

Hosts

Ponderosa pine

Symptoms/Signs

Adult pandora moths are very large and heavy bodied, about 2.5 to 4.0 cm long, with a wingspread of 7 to 11 cm. The forewings are brownish gray and hindwings are light pinkish gray, each marked with a black dot and a dark wavy line. The males are distinguished by having large, feathery antennae. The globular eggs, bluish green to bluish gray, are deposited in clusters of 2 to 50. Early instar larvae are about 5 mm long. They have shiny black heads and black to brownish bodies that are covered with short, dark hairs. Fifth instar larvae grow to about 6 to 8 cm long and are brown to yellowish green. Pupae are dark purplish brown, 2.5 to 3.5 cm long, and have a tough shell.

Biology

The pandora moth has a 2-year life cycle. Adults emerge between late July and late August. The moths mate and females deposit their eggs within a few days. The egg stage lasts at least 40 days and most larvae emerge in October. Larvae are gregarious and extremely cold hearty. They feed in groups on the foliage on warm days throughout the winter. Fifth instar larvae leave the host trees in late June and enter the ground where they pupate. They remain in the pupal stage for the next 12 to 13 months.

Effects

During outbreaks, defoliation can be severe over large areas. Due to the 2-year life cycle, however, defoliation occurs only during alternate years. Outbreaks on the Kaibab Plateau have subsided without causing any lasting damage. However, some growth loss and even mortality can occur especially if trees are severely stressed from additional factors such as drought or heavy dwarf mistletoe infections.

Similar Insects and Diseases

May be confused with sawfly larvae and defoliation. However, sawfly larvae have smooth bodies, are smaller, 18 to 25 mm long, and have eight pairs of leg-like appendages on the abdomen. Defoliation caused by sawflies usually occurs on an individual or small group of trees and is not widespread like that of a pandora moth outbreak.

Defoliation of ponderosa pine caused by pandora moth on the Kaibab NF, Arizona.
USDA Forest Service, Southwestern Region
Adult pandora moth.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Neophasia menapia (Felder and Felder)

Host

Ponderosa pine

Symptoms/Signs

Newly hatched pine butterfly larvae are gregarious feeders on older foliage and then move to the new foliage as they mature. Mature larvae are approximately 2.5 cm long, dark green in color and have light green heads. The body is covered with fine hairs and has two white lateral stripes on the side. Adult moths are white with black markings.

Biology

Adults fly and lay their green eggs from July through October. The eggs overwinter and the larvae hatch the following June or about the time new foliage appears. The small larvae feed in clusters with their black heads oriented toward the tip of the needle. As the larvae mature they feed singly. They pupate in July for approximately 15-20 days.

Effects

This insect has caused spectacular defoliation in the Pacific Northwest, however, it causes little defoliation in the Southwest.

Similar Insects & Diseases

The pine butterfly addult resembles the common cabbage butterfly. In addition, the young larvae feeding in groups may be confused with other gregariously feeding larvae such as sawflies. These would include Neodiprion spp. and Zadiprion spp. of sawflies. Pandora moth is also a defoliator of ponderosa pine. This insect has a 2-year life cycle. Mature larvae are distinctly larger, brown to yellowish green in color and possess stout, branched spines on each body segment.

Larva of pine butterfly.
Michael R. Wagner (Northern Arizona University)
Adult pine butterfly.
Jerald E. Dewey, USDA Forest Service

Scientific Name (s)

Malacosoma californicum (Packard)

Hosts

Aspen, willows, cottonwoods, and mountain mahogany

Symptoms/Signs

Western tent caterpillar is an early season defoliator with feeding damages typically occurring between May and June. Symptoms include moderate to complete defoliation of trees; large silken tents on branches; and presence of larvae in and around the tents. Trees repeatedly defoliated will have sparse foliage, minor branch dieback, and in some cases, tree mortality.

Mature larvae are 4 to 5 cm long and vary widely in coloration. Their heads are blue to black and body color patterns are mixtures of black, orange, and blue. Larvae are usually quite hairy.

Biology

Larvae overwinter as first instars inside egg masses glued around twigs. Larvae emerge from egg masses in spring and construct silken tents on branches that are used for shelter and molting during the daytime. At night, caterpillars feed outside of the tents. As the larvae mature, they disperse and become solitary feeders. Moths emerge from cocoons and following mating glue egg masses to live twigs that are less than 2 cm in diameter.

Effects

Heavy defoliation of aspen for a number of years will cause growth loss and branch dieback. Some mortality may also occur during prolonged outbreaks. Outbreaks, however, are generally short lived, generally lasting 2 to 3 years.

Similar Insects and Diseases

See fall webworm large aspen tortrix and foliar diseases of aspen.

Tents of western tent caterpillar on aspen.
USDA Forest Service, Southwestern Region
Adult western tent caterpillar and egg mass.
Jerald E. Dewey, USDA Forest Service

Scientific Name (s)

Neodiprion spp., Zadiprion spp.

Hosts

Ponderosa pine, piñon

Symptoms/Signs

Pine sawfly larval appearance varies by species and by larval instar, but most are green or yellowish green in color with black, tan or orange head capsules. Larvae are found in either spring-summer or fall-winter feeding gregariously on older foliage, consuming only the outer needle tissue while leaving the central ribs intact. The central ribs later turn yellow brown and break off. Later instar larvae feed singly and consume most of the needle. Eggs are laid in slits cut in the edge of living pine needles. A papery cocoon covers the pupae. Adults are broad waist wasps. Infested trees have sparse foliage and thin crowns.

Effects

Eight species of sawflies infest pines in the Southwest, five of those are found on ponderosa pine. Different species have different preferences for the size of host attacked, and location on the host where they feed. Pine sawflies in the Southwest typically attack open-grown trees or areas where pine is growing at a low density. The same trees are frequently defoliated year after year. In general, defoliation causes slower growth. Repeated defoliation can result in top-kill and tree mortality.

Similar Insects and Diseases

See pandora moth and pine butterfly

Pine sawfly defoliation of ponderosa pine needles showing both early and late instar feeding.
USDA Forest Service, Southwestern Region
Adult female pine sawfly (Neodiprion spp.) oviposting on ponderosa pine.
Michael R. Wagner (Northern Arizona University)

Scientific Name (s)

Lophocampa ingens (Edwards), (=Halisidota ingens)

Host

Ponderosa pine, white pines, and piñon

Symptoms/Signs

Larvae feed on foliage and make large silken webs (tents) in the upper branches of host pines. Mature caterpillars are about 4 cm long, reddish brown to black in color and have tufts of black and yellow hairs on their back. Adult moths have dark forewings with large, white splotches and white hindwings.

Biology

The tiger moth has one generation per year in the Southwest. Adult moths emerge and lay eggs in August. During September and October caterpillars hatch from eggs, begin feeding on pine needles and producing webbing. Larvae overwinter in the webs in groups. In April and May, larvae resume feeding and expand their webs. At this point the insects and the webs become very noticeable. In June pupation occurs.

Tiger moths are also found feeding and forming tents on Douglas-fir and white fir during outbreaks. It is believed that populations of this insect usually remain at low levels due to the action of predators, parasites, diseases, and cold winters.

Effects

Larvae feed gregariously in webs primarily on young piñon and ponderosa pine. Although the webs and larvae can be very noticeable in spring, this insect causes minor defoliation. Permanent tree injury rarely results from feeding that is usually limited to the upper foliage.

Similar Insects

Tents are similar to those formed by tent caterpillars such as the western tent caterpillar; however, L. ingens is the most common moth to make large tents on piñon, ponderosa, and white pines. Another species of tiger moth, L. argentata subalpina, feeds primarily on juniper and occasionally on piñon in the Southwest.

Tents and damage of ponderosa pine by tiger moth.
USDA Forest Service, Southwestern Region
Adult tiger moth.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Choristoneura conflictana (Walker)

Host

Aspen

Symptoms/Signs

Presence of flat egg masses on the upper surface of foliage, partially eaten rolled-up leaves in which small, green to black larvae are feeding or pupating, incomplete defoliation before the buds have expanded in the spring.

Biology

Pale green egg masses are laid in large, flat masses on the upper surfaces of the foliage in June and July. Second-instar larvae overwinter in silken hibernacula in bark crevices and other out-of-the-way places. The small larvae begin to migrate up the stems of aspen on warm days in early spring. The larvae mine the buds, sometimes causing complete defoliation before the buds open. Later stage larvae roll the leaves into shelters within which they feed and eventually pupate. The moths have a wingspread of 25 to 30 mm. The forewing is grayish with basal, middle, and outer brownish patches. There is one generation annually.

Effects

During outbreaks, this insect can completely defoliate aspen stands. Outbreaks characteristically last 2 to 3 years and can result in growth loss and some twig and branch dieback.

Similar Insects

Larvae and pupae are similar to those of the western spruce budworm. However, the larvae of the large aspen tortrix are green to grayish-black with a black head capsule while the western spruce budworm larvae are white to grayish-tan with a tan head capsule and feed on Douglas-fir, true firs, and spruce.

Closeup of damage caused by large aspen tortix and larva.
Minnesota DNR, Minnesota Department of Natural Resources Archives
Adult large aspen tortix.
Edward Holsten, USDA Forest Service

Scientific Name (s)

Orgyia pseudotsugata (McDunnough)

Hosts

Douglas-fir, white fir and spruce

Symptoms/Signs

The caterpillar of the Douglas-fir tussock moth is grayish with brightly colored tufts of hair and a shiny black head. There are also two long horns of black hairs behind the head and another at the rear of the body. In the Southwest, feeding often causes severe or nearly complete defoliation, which often leads to top kill or tree mortality. Small cocoons and egg mass cases are attached to the underside of twigs and branches.

Biology

Eggs hatch from mid-May to early June and caterpillars feed on the current year's developing foliage. Young larvae are 4 to 7 mm long and covered with long, thin body hairs that later develop into tufts. Because the female moth is wingless, the primary means of dispersal from tree to tree is by windblown larvae. Young larvae congregate on the tops of defoliated trees and drop by silken threads that may be over 3 meters long. These threads eventually break from the tree and give a ballooning effect to the larvae. Mature larvae are about 20 to 30 mm long with a gray or brown body and a shiny black head. Two long hair pencils project forward from behind the head and another occurs at the rear of the body. Four tufts of brown or cream-colored hairs and red spots occur on the first four and last abdominal segments. Some people develop an itchy rash from exposure to the frequently airborne caterpillar hairs. After the caterpillars are about half-grown, they feed on all age classes of needles throughout the crown. Pupation occurs inside a thin, silk cocoon spun on the undersides of branches from late July to the end of August. Adults emerge shortly afterwards and the flightless female deposits egg masses on twigs and branches.

Effects

Severe outbreaks can cause significant mortality of both overstory and understory trees relatively quickly (1 or 2 years). Top-kill occurs in less severe outbreaks. Bark beetle epidemics can occur in tussock moth defoliated areas.

Similar Insects and Diseases

Early damage and webbing in trees may be similar to that caused by western spruce budworm ; however, the larvae are very distinct.

Douglas-fir tussock moth-caused damage to white fir in the Sandia Mountains, New Mexico.
USDA Forest Service, Southwestern Region
Adult female Douglas-fir tussock moth on egg mass. Note that female moth is wingless.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Hyphantria cunea (Drury)

Hosts

Willow, alder, ash, chokeberry, cottonwood, madrone, and walnut

Symptoms/Signs

Larvae feed on foliage, forming large webs in the branches of trees. Webs are noticeable in the fall when larval feeding takes place. There are two races:a blackheaded or northern race and a redheaded or southern race. Larvae of the southern race are yellowish-tan with red or orange colored heads and brownish hair that arises from reddish-brown tubercles. Larvae of the northern race have a black head with a pale yellowish or greenish body that has a dark stripe on the back, and long white hairs rising from red or black tubercles. The black-headed race predominates in the West. Adults are white in color with orange markings on the body and legs. The wings have some black spots and a wing expanse of approximately 30 mm.

Biology

Fall webworm has one generation per year. Adults appear and lay eggs in late June and early July. The eggs hatch and the small larvae feed on both leaf surfaces while larger larvae will consume the whole leaf. Larval feeding continues until mid-September. The insect overwinters in the pupal stage in a transparent cocoon in the soil, leaf litter, or on tree trunks.

Effects

This insect causes minor defoliation in most forested situations. It can cause loss of visual quality in ornamental plantings.

Similar Insects and Diseases

The western tent caterpillar is sometimes confused with the fall webworm, due to both having dark heads and dark stripes down their backs. However, western tent caterpillar feeds in the spring while fall webworm feeds in the fall.

Larvae of fall webworm.
USDA Forest Service, Southwestern Region
Adult and pupa of fall webworm.
Gerald J. Lenhard, Louisiana State University

Scientific Name (s)

Epinotia meritana (Heinrich)

Host

White fir

Symptoms/Signs

Larvae mine the needles, resulting in bleached-yellow needles from late spring to early fall. Mature larvae are about 8 mm long, yellowish-green to cream colored, with brown to black heads. Pupae are orange to dark brown, about 5.5 mm in length, and can often be seen protruding from the hole in the mined needle prior to emergence. The adults are 11 mm dusty gray moths. They can be seen swarming around host trees in late June and July.

Biology

The white fir needleminer has one generation per year in New Mexico and Arizona. Eggs are deposited, usually one per needle, in late June and July. Eggs hatch in August and September. Young larvae immediately bore into the needle where they overwinter. As weather warms in the spring, feeding begins. Each larva can mine several 1-year-old needles. Two- and three-year-old needles are also mined during outbreak conditions when insect populations are high. Two to six needles are usually webbed together and remain on the tree for the duration of the summer. Pupation occurs within the last mined needle in June or early July. Adult moths emerge in 10 to 14 days after pupation. Mating occurs within 2 to 3 days of emergence.

Effects

After several consecutive years of heavy defoliation, a high proportion of limb mortality and widespread tree mortality may occur. This can give individual trees or even entire stands a silvery appearance. These heavily defoliated stands decline in vigor and may be predisposed to attack by fir engraver beetle.

Similar Insects and Diseases

Similar defoliation may be caused by western spruce budworm or Douglas-fir tussock moth; however, the larvae of white fir needleminer only mine inside the needles.

Closeup of white fir needleminer defoliation to white fir.
USDA Forest Service, Southwestern Region
Defoliated white fir caused by the white fir needleminer.
USDA Forest Service, Southwestern Region

Mistletoes

Mistletoes are parasitic plants that slowly weaken and eventually kill their host trees. There are two types of mistletoe in North America, true mistletoe (Phoradendron) and dwarf mistletoe (Arceuthobium). Both are parasitic on the stems of woody plants from which they derive water and mineral nutrients. True mistletoes produce most of their organic nutrients by their own photosynthesis and are believed to obtain little from the host. Although photosynthetic, dwarf mistletoes are dependent on the host for carbon nutrients for growth and reproduction. Dwarf mistletoes are generally considered to be more damaging than true mistletoes; however, host mortality associated with either type of mistletoe infection can occur during periods of drought when lack of stomatal closure of leaves of the parasite causes fatal water loss of the host.

Dwarf mistletoes are the most common pathogens in Southwestern coniferous forests. They are parasitic, seed-bearing plants that depend on their hosts almost completely for water and nutrients. Dwarf mistletoes are natural components of many forest ecosystems in the West, having co-evolved with their hosts for hundreds of thousands of years. There are eight species in the region, each typically having one preferred host species.

Ponderosa pine dwarf mistletoe (generally referred to as southwestern dwarf mistletoe to distinguish it from a different species affecting ponderosa pine in California and the Northwest; it has recently been referred to as pineland dwarf mistletoe by some) has long been recognized as the most damaging disease of ponderosa pine in the Southwest. It occurs in over one-third of the ponderosa pine acreage in the region. Douglas-fir dwarf mistletoe occurs in roughly one-half of the mixed conifer acreage in the region. Other species of dwarf mistletoe have more limited distributions (see table).

Hosts

See table (below)

Symptoms/signs

Aerial shoots of dwarf mistletoe plants vary by species in size, color, and pattern of branching. For example, southwestern dwarf mistletoe of ponderosa pine are often bright orange and conspicuous, and those of Douglas-fir dwarf mistletoe are often small and inconspicuous. Host branches and stems are often swollen at the site of dwarf mistletoe infections. Witches’ brooms develop from either systemic infections or as a result of discrete, localized infections. The size and extent of brooms varies among dwarf mistletoes and their host.

Biology

Dwarf mistletoes have separate male and female plants. Seeds are produced annually on female plants. These are explosively released (typically 1 to 12 meters), and stick to host material. Upon germination, dwarf mistletoes produce an endophytic system, a specialized rootlike structure that is in contact with the phloem and xylem of host trees, from which the parasite obtains nutrients and water. Aerial shoots appear 3 to 5 or more years after infection; the period before shoots are visible is known as the latent period.

Spread of dwarf mistletoe occurs both from tree to tree and within the crowns of individual trees. Infections tend to build up initially in the lower half of a crown and gradually spread upward. Lateral spread of dwarf mistletoe through single-storied stands averages about 0.5 meter per year. Spread is relatively rapid from infected overstory trees to nearby regeneration.

Effects

As parasites, dwarf mistletoes cause significant changes in physiological processes and structural characteristics of infected trees, resulting in changes in the structure and function of forest communities. Tree growth and vigor usually decline when more than half the crown is parasitized. Most infected trees can survive for several decades; generally smaller trees decline and die more quickly than larger ones. Tree mortality in areas with extensive infection is often three to four times higher than in uninfested areas. Bark beetles frequently attack heavily infected trees, especially during drought.

Extensive dwarf mistletoe infection greatly reduces forest productivity. On the other hand, infection has some benefits for wildlife. Large witches' brooms can serve as ideal nesting platforms for birds and small mammals, and snags create habitat for cavity nesting birds. A few species (most notably the blue grouse) are known to eat dwarf mistletoe shoots, although none depend on it as a primary food source.

Similar Insects and Diseases

Some fungi cause the formation of witches' brooms, including broom rusts in white fir and spruce and Elytroderma needle cast in piñon, ponderosa, and southwestern white pines. Where brooms are observed, branches should be checked for the presence of aerial dwarf mistletoe shoots to distinguish broom symptoms caused by other pathogens or physiological disorders.

**Principal Hosts and Distribution of Dwarf Mistletoes in Arizona and New Mexico**
Common Name	Species	Principal Host	Distribution
Southwestern dwarf mistletoe	Arceuthobium vaginatum subsp. cryptopodum (Engelmann) Hawksworth & Weins	Ponderosa pine	Throughout host type
Douglas-fir dwarf mistletoe	Arceuthobium douglasii Engelmann	Douglas-fir	Throughout host type
Western spruce mistletoe	Arceuthobium microcarpum (Engelmann) Hawksworth & Weins	Engelmann spruce, Blue spruce, and Bristlecone pine	Limited portions of host type, although common in eastern and central Arizona
Pinyon dwarf mistletoe	Arceuthobium divaricatum Engelmann	Piñon	Throughout the Southwest, except southeast Arizona
Apache dwarf mistletoe	Arceuthobium apachecum Hawksworth & Weins	Southwestern white pine	Eastern and southeastern Arizona, central and southern New Mexico
True fir dwarf mistletoe	Arceuthobium abietinum f. sp. concoloris Engelmann ex Munz	White fir	North rim of Grand Canyon National Park, Santa Catalina and Chiricahua Mts., AZ
Chihuahua pine dwarf mistletoe	Arceuthobium gillii Hawksworth & Weins	Chihuahua pine	Mostly southeast Arizona, but some in central
Blumer’s dwarf mistletoe	Arceuthobium blumeri A. Nelson	Southwestern white pine	Huachuca Mts., Arizona

Female southwestern dwarf mistletoe.
USDA Forest Service, Southwestern Region
Male southwestern dwarf mistletoe.
USDA Forest Service, Southwestern Region
Apache dwarf mistletoe on southwestern white pine.
USDA Forest Service, Southwestern Region
Spruce dwarf mistletoe.
USDA Forest Service, Southwestern Region
Female Douglas-fir dwarf mistletoe.
USDA Forest Service, Southwestern Region
Male Douglas-fir dwarf mistletoe.
USDA Forest Service, Southwestern Region

True mistletoes are commonly known as the Christmas or leafy mistletoes. There are eight species in the Southwest, all within the genus Phoradendron . Three species occur on hardwoods, the other five infect conifers. Phoradendron macrophyllum has a very broad host range, occurring on most riparian tree species, while the other true mistletoes are genus specific.

Hosts

See table (below)

Symptoms/signs

True mistletoes are flowering plants with thick green stems. Plants are often round in form and up to 1 meter in diameter, depending on the species. Hardwood true mistletoes have thick green leaves that are nearly oval in shape, contrasting with conifer true mistletoes, which have small thin leaves or are nearly leafless. The small, sticky berries are white, pink or red and are ripe from October to January, depending on the species. Evergreen clumps of mistletoe are readily observed on bare deciduous trees in winter.

Biology

Fruit-eating birds distribute the seeds in their droppings or by wiping their beaks. Some bird species swallow the fruit whole and disperse the seeds to another tree, while other bird species pick out the seed, leaving it on the host plant, and swallow only the pulp.

When the seeds germinate a modified root penetrates the bark of the host and forms a connection through which water and nutrients pass from the host to the mistletoe. It takes approximately 2 to 3 years for shoots to develop, following initial infection, and another year before the plant is producing berries.

Effects

Young or small trees are seldom infected by true mistletoe. In nearly all cases, initial infection occurs on larger or older trees because birds prefer to perch in the tops of taller trees. Severe buildup of mistletoe often occurs within an infected tree because birds are attracted to and may spend prolonged periods feeding on the mistletoe berries. True mistletoes are not aggressive pathogens. They use the host xylem as a water source and do not cause mortality until water availability to the host is limited. In some hosts, infected portions of the tree often exhibit galls on branches or burls in the trunk. On oaks, sycamores, and cottonwoods, branch dieback is associated with galls formed by the corresponding mistletoe.

Similar Insects and Diseases

Deformities caused by canker and rust fungi can resemble those caused by mistletoe.

Principal Hosts and Distribution of True Mistletoes in Arizona and New Mexico
Common Name	Species	Principal Host	Distribution
Bigleaf mistletoe	Phoradendron macrophyllum (Engelm.) Cockerell	Most riparian hardwood species, except oaks	Throughout lower elevation riparian areas of both states
Southwestern oak mistletoe	Phoradendron coryae Trel.	Oak species	Throughout live oak woodlands and lower elevation gambel oak areas of both states
Desert mistletoe	Phoradendron californicum Nutt.	Leguminous trees and shrubs (e.g. Mesquite ( Prosopis spp.) Acacia (Acacia spp.) Palo Verde ( Cercidium spp.) ironwood ( Olneya spp.)	Throughout the ranges of host types in Arizona and extreme southwest corner of New Mexico
Juniper mistletoe	Phoradendron juniperinum Engelmann	All juniper species	Throughout juniper woodlands of Arizona and New Mexico
Hairy juniper mistletoe	Phoradendron capitellatum Torr. ex Tel.	Utah, alligator and red-berry juniper	Southern Arizona and southwest New Mexico
Texas juniper mistletoe	Phoradendron hawksworthii Wiens & CG Shaw	Alligator and one-seed juniper	Southeastern New Mexico
Dense mistletoe	Phoradendron densum Torr. ex Tel.	Arizona cypress	Central Arizona
White fir true mistletoe	Phoradendron pauciflorum Torr.	White fir	Santa Catalina Mountains of southeast Arizona

Phoradendron pauciflorum often kills tops of infected white fir.
USDA Forest Service, Southwestern Region
Phoradendron hawksworthii on juniper in New Mexico.
USDA Forest Service, Southwestern Region
Phoradendron densum on Arizona cypress.
USDA Forest Service, Southwestern Region
True mistletoes are easy to spot on deciduous trees like this mesquite tree.
USDA Forest Service, Southwestern Region
Desert mistletoe plants are red when full of fruit.
USDA Forest Service, Southwestern Region
Phoradendron californicum has red berries that ripen in winter.
USDA Forest Service, Southwestern Region
Phoradendron macrophyllum on Arizona sycamore.
USDA Forest Service, Southwestern Region
True mistletoe on juniper.
USDA Forest Service, Southwestern Region
Phoradendron juniperinum with pink ripe berries.
USDA Forest Service, Southwestern Region
Phoradendron coryae in December.
USDA Forest Service, Southwestern Region

Non-Infectious Disorders

The symptoms of noninfectious, or abiotic, disorders closely resemble those of some parasitic diseases making it difficult to determine the cause. Some of these disorders serve as an entry for pathogens, such as canker and wood decay fungi.

Burls are large woody, more or less hemispheric, swellings on the main stems of trees. Although some stem swellings are the result of pathogens, often the cause of burls is unknown. Burls may often bear many buds or sprouts.

The cause of burls is often unknown.
USDA Forest Service, Southwestern Region

Water deficit develops as a normal phenomenon in plants when water loss by transpiration exceeds the rate of absorption from soil. Chronic injury results from long-term exposure to low water supplies (e.g. in areas with poor soils) and is expressed by growth loss and increased susceptibility to parasitic fungi and insects. Acute injury occurs under extreme water deficiency and is expressed by significant growth loss or death. Symptoms of drought damage include wilting, discoloration of foliage and premature leaf fall. Progression within the crown is from the top down and outside in, and the roots are usually the last portions to die. Symptoms can be similar to those of trees suffering from root disease, except that with root diseases, the roots die before the foliage. In the Southwest, drought symptoms have been observed in many trees including aspen, ponderosa pine, piñon, and soapberry.

Winter drought is particularly harmful in Southwestern upland forests and can render large areas vulnerable to bark beetles and wildfire.

Aspen branch dieback during summer drought.
USDA Forest Service, Southwestern Region
Western soapberry with branch dieback following dry spring.
USDA Forest Service, Southwestern Region

Frost damage of many tree species including aspen, locust, spruce, and oak has been observed throughout the Southwest. The tolerance of foliage and small branches to cold temperature depends on their“hardiness,” which is closely correlated with the time of year and species. Temperatures just above freezing and short photoperiods induce frost hardiness. The sudden onset of below-freezing temperatures (frosts) in spring or early autumn can severely damage unhardened tissues, killing young shoots and leaves or needles.

As temperatures rise in late winter and early spring, plants deacclimate until, by the time growth begins, they can no longer tolerate more than a few degrees of frost. Leaves and stems killed by spring frost are usually small and succulent at the time of injury. More mature leaves and stems can tolerate lower temperatures. After thawing, damaged tissues at first appear water soaked and soon become shriveled and reddish brown, dark brown, or black, depending on the species. Dead leaves and shoots break off or abscise during the next several weeks. New shoots and leaves begin to grow almost immediately and soon mask the early season damage.

Newest and most sensitive growth of fir killed by frost.
USDA Forest Service, Southwestern Region
Aspen leaves succumb to June frost.
Borys Tkacz (USDA Forest Service, Washington Office)

Most lightning struck trees are only superficially damaged, but approximately 2 percent of the annual tree mortality in the region has been attributed to lightning. Killed trees are either blown apart at impact or soon colonized by bark beetles, or both. Damage is in the form of a long narrow furrow in which the bark is removed and a narrow band of wood exposed. Sometimes lightning damage results in internal decay that may provide cavity-nesting habitat for wildlife.

Many lightning struck trees survive for decades and are slowly decayed.
USDA Forest Service, Southwestern Region
Lightning struck trees are often attacked by bark beetles.
USDA Forest Service, Southwestern Region

Red belt, another type of winter damage, is named because of the appearance of red needled trees distributed in well-defined bands varying from less than 20 to as much as 1,000 yards wide on slopes and benches. These events are associated with the sudden occurrence of warm, dry winds (e.g. Chinook winds) that produce a temperature inversion. A relatively thin layer of warm air arrives that cannot mix downward and continues to contact side slopes. Trees exposed to unseasonably warm air by day receive seasonably cold air at night. This alteration of warm and cold air exposure, along with the frozen condition of the soil, results in desiccation injury because daytime transpiration removes moisture from the needles more rapidly than roots in frozen soil can replace it. Later, older needles fall off, leaving only current year needles on living branches after bud-break.

A band of cold air gets trapped at a specific elevation around mountains.
USDA Forest Service, Southwestern Region

The uptake of salts by the roots of roadside trees is a common problem wherever sodium chloride, calcium chloride, and/or magnesium chloride are applied to de-ice highways in the winter or for dust abatement in the summer. Symptoms start as tip burn with the bases of the needles still green. Damage progresses with the continuation of salt application; first terminal growth of branches ceases, eventually followed by mortality.

Most tree species experience tip burn from salt damage.
Borys Tkacz (USDA Forest Service, Washington Office)
Damage from the application of de-icing salts along roadways appears on hardwood trees in the summer.
USDA Forest Service, Southwestern Region

More severe windthrow damage takes place with tornadoes and microbursts, which are occasional events in the Southwest. Tornadoes and microbursts both result in windthrown trees lying parallel to one another in the same direction as the wind. Tree species with shallow root systems (e.g. spruce) are more prone to windthrow.

Tornadoes and microbursts have been known to knock down a swath of trees.
USDA Forest Service, Southwestern Region
There are typically decay or soil defects associated with windthrown trees.
USDA Forest Service, Southwestern Region

There are several different types of winter damage of conifers in the Southwest. Water deficit can develop in dormant evergreens during warm weather in late winter or early spring when needles transpire water from leaves and stems while the soil is cold or frozen. Roots extract insufficient water from cold soil and none from frozen soil. Freeze damage occurs when needles no longer have enough moisture to survive normal nighttime temperatures. Freeze damage can also follow untimely deacclimation from temporary warm weather. Ponderosa pine and alligator juniper are the species most often observed with damage by these phenomena. Sometimes the result is trees that have needles with brown tips and green bases, and other times trees may have winter-killed needles that are completely brown regardless of age, but the branch and bud tissues are still green and viable. In either case, trees recover during the growing season. Occasionally, severe freeze damage near the upper elevational limits of a particular tree species causes mortality or topkill.

Winter injury can be mistaken for mortality at a distance.
USDA Forest Service, Southwestern Region
Needle bases of 1-year needles are green but tips are brown.
USDA Forest Service, Southwestern Region

Root Disease

Root disease fungi affect all tree species in the Southwestern Region, with Douglas-fir, true firs, spruce, and aspen being the most susceptible to damage. Susceptibility also varies by tree age, genetics, type of root disease pathogen present and site history.

Root disease or decay fungi spread from roots of diseased trees to those of healthy ones. They start in a tree or stump and spread slowly outward in all directions, resulting in a slowly enlarging group of dying and dead trees. The oldest mortality is located at the center of infection with a fringe of recently killed and dying trees around the outer edge. In the Southwest, these“centers” of disease are small in size, typically less than 1 acre.

Root disease is referred to as“a disease of the site” because the fungi colonize dead and dying trees and remain in dead roots and soils for many years. Many of these fungi have the ability to act as both pathogens in live trees and saprophytes in dead wood material. Not only are the current trees affected, but also trees that become established in the future. Some root disease fungi have been shown to remain alive and active in infested sites for more than 50 years.

The aboveground symptoms of trees affected by root disease include chlorosis, reduced needle length, progressive thinning of foliage, fading crown, reduced tree growth, and death. These symptoms are similar to those caused by drought, high water table, and bark beetle attack. However, the decline of trees affected by root disease usually extends over a period of a few to several years and not all trees succumb at the same time. The other causes of decline kill trees more rapidly, generally in 1 to 2 years, and a group of trees all die at the same time. Bark beetles commonly attack trees weakened by root disease infection.

The incidence of root disease often relates to the amount of human activity in forest sites. Harvesting timber from infected stands often increases root disease activity. In addition, changes in forest structure brought about by fire suppression and selective logging have led to increases in tree species more prone to root disease.

Scientific Name (s)

Heterobasidion irregulare Garbelotto & Otrosina, Heterobasidion occidentale Otrosina & Garbelotto

Hosts

irregulare: Ponderosa Pine
occidentale: White fir, subalpine fir, Engelmann spruce

Symptoms/signs

Fruiting bodies of Annosus are grey-brown on the upper surface with an undersurface that is chalky white with pores. They are found on the underside of decayed roots and slash, inside stumps (common in the Southwest), or under the duff at the base of infected stumps and trees (rare in the Southwest). Annosus root disease leads to crown thinning and mortality or windthrow, the latter of which can occur before aboveground symptoms are evident.

Biology

Spores are produced on conks in decayed stumps or on roots of windthrown trees. The most common means of initial entry of Annosus root into a site is via airborne spores that germinate on freshly cut stumps and basal wounds. Mycelium of Annosus root quickly colonizes the stump and grows into its roots. Transmission to adjacent trees occurs via root contacts. In live trees, the fungus decays woody root systems and then advances to the root collar where it may surface to the cambium and kill by girdling, as in ponderosa pine, or progress more slowly through roots to the stem and cause butt decay, as in true fir.

There are two species of Heterobasion that cause root disease in North America, each with specific host preferences. In Arizona and New Mexico, H. occidentale infects white fir and sometimes spruce and subalpine fir, and H. irregulare infects ponderosa pine. Like Armillaria, the Heterobasidion fungi are common decays of dead woody material as well as pathogens.

Effects

This is one of the most importatnt forest tree diseases in temperate zones worldwide. Damage to forests in North America has been most severe in the Southeast, where intensive forestry has exacerbated the disease due to providing stumps for colonization. In the Southwest, H. occidentale is a common root disease of white fir, but H. irregulare is fairly rare in ponderosa pine by comparison. For both species, infected trees are predisposed to attack by bark beetles.

Similar Insects and Diseases

The aboveground symptoms are similar to those caused by other root disease fungi.

Laminated decay in the lower bole and roots indicative of annosus root disease.
USDA Forest Service, Southwestern Region
Fruiting bodies of Heterobasidion irregulare. Fruiting bodies can be difficult to find. They are commonly located inside hollow stumps and root cavities.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Leptographium wageneri (W.B. Kendr.) M.J. Wingf.

Hosts

Piñon and Douglas-fir

Symptoms/signs

Like other root diseases, black stain usually exhibits symptoms of gradual crown decline before tree death. In the early stages of decline, terminal growth is reduced and older needles become chlorotic. As the disease progresses, older needles are shed prematurely, new needles are somewhat stunted and yellow, and reduced internodal growth is evident on lateral branches. Very small trees may succumb quickly without exhibiting gradual crown decline symptoms.

Black stain root disease is distinguished from other root diseases by the dark-brown to purple-black discoloration in the sapwood of the lower bole and root collar. When observed in cross section, the black stain appears in arcs roughly concentric with the growth rings.

Biology

The Southwestern Region has two physiologically and morphologically distinct variants of black stain root disease. Leptographium wageneri var. wageneri is pathogenic to piñons and L. wageneri var. pseudotsugae T.C. Harr. &F.W. Cobb causes black stain in Douglas-fir. Both of these have been found in New Mexico but not in Arizona. A third variety L. wageneri var. ponderosum infects hard pines in California but has not been found in the Southwest.

Effects

Black stain root disease fungi grow in sapwood and plug tracheids, which prevents water transport and causes a wilting and rapid tree decline and death. Unlike species of Armillaria and Heterobasidion, L. wageneri does not cause wood decay and dies with its host.

Black stain root disease affects groups of trees in distinct infection centers. Typical infection centers have trees in various stages of decline near the perimeter and dead trees in the interior where infection originated.

Similar Insects and Diseases

Blue stain fungi, which are often confused with black stain fungi, are usually a lighter color and typically are wedge-shaped in cross-section, and they can discolor the entire sapwood radius.

Black stain of piñon caused by Leptographium wageneri.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Phaeolus schweinitzii (Fr. :Fr.) Pat.

Hosts

Douglas-fir, ponderosa pine, southwestern white pine, spruce, and true firs

Symptoms/signs

Trees infected with Phaeolus schweinitzii do not typically show outward symptoms, so the presence of disease is usually not realized until a tree breaks or is windthrown due to loss in structural support. The fruiting bodies of P. schweinitzii often emerge through soil from decayed roots. They have a velvety surface which is yellow to orange at first, then turning brown with a yellow margin. It turns a dark red brown upon aging, is crumbly and can be mistaken for a cow pie at this point, hence the nickname“the cow patty fungus.” Incipient decay appears as a light yellow to pale reddish-brown color. As the decay advances, the color intensifies and the wood rapidly loses strength. In advanced stages of decay, the wood breaks up into large cubes that are crushed easily, and the butt portions of infected trees can be swollen.

Biology

Spores likely initiate most P. schweinitzii infections. Phaeolus schweinitzii is unusual in that the fungus establishes itself in forest soil and enters trees through root tips. There is no root-to-root spread as used by other root disease causing fungi. Decay is confined to the roots and lower 1-2 m of the butt log, rarely extending much higher.

Effects

Schweinitzii root and butt rot is a major disease of older trees. It causes decay of the roots and lower stem and the resulting strength loss predisposes trees to windthrow and breakage.

Similar Insects and Diseases

The fruiting bodies of Onnia spp. are similar to P. schweinitzii since they are all velvety on top when fresh and have a pore surface beneath. However, P. schweinitzii fruiting bodies are larger, greater than 15 cm in circumference, while the other two are about 5 cm maximum.

A young and colorful specimen of Phaeolus schweinitzii.
USDA Forest Service, Southwestern Region
Fruiting structures of Phaeolus schweinitzii popping up from decayed roots.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Ganoderma applanatum (Pers.) Pat.

Host

Aspen

Symptoms/signs

Infected trees often break or fall before death, however, a fruiting body or conk can be found at the base of most infected trees. The tough semicircular conk is usually found near ground level. It has a brown upper surface with a white rim and an undersurface that is white and stains when touched or scratched. The latter trait allows for artistic expression that is permanent if the conk is allowed to dry. Gandoderma applanatum produces advanced white-mottled decay in the large roots and lower parts of the stem.

Biology

Ganoderma applanatum infection occurs at wounds and the fungus attacks sapwood, heartwood, and cambium. The white-mottled rot is usually concentrated in large roots (larger than 5 cm in diameter) and base of the stem, but can extend up into the trunk for a meter or more. The larger roots are believed to act as avenues of spread to new hosts.

Effects

Ganoderma applanatum is found in almost all aspen stands but is more abundant on moist sites with deep soils. Windthrow is common.

Similar Insects and Diseases

Although there are other root decay fungi of aspen, G. applanatum is the most prominent and the only one that produces a tough woody-conk at ground line in live trees in the Southwest.

Trees often topple over due to severe decay of major roots.
USDA Forest Service, Southwestern Region
Ganoderma applanatum conks are often found at the base of infected trees.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Armillaria spp.

Hosts

Douglas-fir, spruce, true firs, oaks, and ponderosa pine.

Symptoms/signs

The most diagnostic trait of Armillaria is the thick, fan-shaped mat of white mycelium in the cambium of roots and root crown. This may be accompanied by copious resin flow on bark surfaces, although this trait is not common in the Southwest. Other signs of the fungus include rhizomorphs, or black shoestring-like structures, on the outside of infected roots. The fruiting bodies of this fungus are commonly produced in clusters but can be found singly. The caps are yellow brown to dark tan, with small scales on upper surface. The stem is stout, tapering upward to a ring of tissue just below the cap. The decay is light yellow, soft and spongy to stringy often containing numerous black zone lines.

Biology

Armillaria root decay spreads primarily by rhizomorphs and root contacts. Armillaria invades the bark and cambial region of roots and the root collar, killing roots and trees of all sizes. Wood decay follows cambial attack, and the wood serves as a source of energy necessary for infection of new hosts. New infections are less common, occurring when mushrooms release windborne spores that germinate and colonize recently killed material. As with other root disease fungi, Armillaria can persist for decades in decaying wood in soil.

Armillaria often acts in conjunction with other secondary pests and pathogens. For example, Dendroctonus and fir engraver beetles may attack trees with this root disease.

Effects

Armillaria is the most common root disease in the Southwest and may account for up to 80 percent of the root disease conifer mortality in the region. There are over 10 species of Armillaria, some are virulent parasites while others are opportunists that act selectively on small or weak individuals such as those shaded by taller plants, defoliated by insects, attacked by other fungi, or weakened by drought.

Similar Insects and Diseases

Other fungi such as Fomitopsis pinicola produce white mycelium beneath the bark of infected stumps, but the mycelium is not thick and fan-shaped like that produced by Armillaria spp., and F. pinicola produces a brown cubicle rot.

Decay of Armillaria is soft and spongy.
USDA Forest Service, Southwestern Region
Fruiting bodies of Armillaria spp.
USDA Forest Service, Southwestern Region

Scientific Name (s)

Onnia tomentosa (Fr. :Fr.) P. Karst.

Hosts

Spruce and Douglas-fir

Symptoms/signs

Fruiting bodies of Onnia tomentosa most commonly develop in August and September. They are small (usually less than 10 cm in diameter), mushroom shaped, and have a lower pore surface from which the spores are released. Although leathery, they are annual. The upper surface is yellow-brown to rust-brown and velvety, and becomes dark brown with age. The early stage of decay is characterized by a red-brown discoloration in the heartwood of roots. The late stage is also reddish brown but appears lighter because of numerous small elongate pockets with pointed ends, filled with white mycelium. This type of decay is known as a white pocket rot. The most distinctive characteristic of Tomentosus rot is that a cross section of an infected stem in advanced stages of decay has a honeycomb appearance.

Biology

Tomentosus root disease spreads primarily by root-to-root contact, however, infection by spores can occur through deep wounds in roots. There is no evidence that spores colonize stump surfaces as with Annosus root disease. Diseased trees occur singly or in groups. The fungus spreads both outward in roots and up into the butt. Diseased roots have dead, decayed distal portions and red-brown, resin-soaked wood extending into the living portion and the butt. Advanced decay develops slowly and expands to involve both deep-lying wood and sapwood near the cambium. Infected trees often die standing, but sometimes blow over while alive because of advanced decay in major roots or butt. Onnia tomentosa has been found to persist for more than 50 years in decaying wood in soil.

Effects

Although Tomentosus root disease has been observed in spruce/fir and transition forests throughout the Southwest, there is little information available on the extent and damage from this disease. In other parts of the country, blowdown caused by Tomentosus root disease has initiated spruce beetle (Dendroctonus rufipennis) outbreaks but that has not been reported here.

Similar Insects and Diseases

Onnia tomentosa and O. circinata are nearly identical and difficult to differentiate macroscopically. Microscopically, O. circinata can be differentiated from O. tomentosa based on hooked structures the latter does not produce. Onnia tomentosa and O. circinata are sometimes called false velvet-top fungi, because of the similarity of the conks of these fungi with that produced by Phaeolus schweinitzii, which is the real velvet-top fungus.

Red-brown discoloration of roots decayed by Onnia tomentosa.
Borys Tkacz (USDA Forest Service, Washington Office)
Leathery Onnia tomentosa fruiting body.
John H. Ghent, USDA Forest Service

Submit a Specimen

Both zone offices are equipped to receive forest insect or disease specimens submitted from the field for identification. Specimens may be shipped to the appropriate zone office (addresses shown below). The following procedures for collecting and shipping specimens should be used:

Collect the specimen

Adequate material should be collected.
Record adequate information including:
- Location of collection
- When collected
- Who collected the specimen
- Host description (species, age, condition, etc.)
- Area description (forest type, site conditions, etc.)
- Unusual conditions (frost, poor drainage, etc.)
- Personal opinion of the cause of the problem may be helpful
Pack the specimen
- Larvae and other soft-bodied insects should be shipped in small screw-top vials or bottles containing at least 70 percent isopropyl (rubbing) alcohol.
- Make sure bottles are well sealed.
- Pupae and hard-bodied insects may be shipped either in alcohol or in small boxes.
- Specimens should be placed between layers of tissue paper in the boxes.
- Pack carefully and make sure there is little movement of material within the box.
- Do not pack insects in cotton.
- Needle or foliage diseases: Do not ship in plastic bags as condensation can become a problem.
- Use a paper bag or wrap in newspaper.
- Pack carefully and make sure there is little movement within the box.
- Mushrooms and conks: Do not ship in plastic bags.
- Either pack and ship immediately or air-dry and pack.
- To pack, wrap specimens in newspaper and pack into a shipping box with more newspaper.
- If on wood, include some of the decayed wood.
Submit the specimen

Arizona Zone Forest Office

2500 South Pine Knoll Drive
Flagstaff, AZ 86001
New Mexico Zone Forest Office

333 Broadway Ave SE
Albuquerque, NM 87102

References

Branch Insects

Pine Seed Chalcid

Beatty, J. 1979. Forest insect and disease conditions in the Southwest 1979. USDA Forest Service, Southwestern Region Publication 80-7, 29 pp.
Coulson, R.N. and J.A. Witter. 1984. Forest Entomology:Ecology and Management. John Wiley & Sons, New York, NY. 669 pp.

Cone Beetles

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Hedlin, A.F., H.O. Yates, D.C. Tovar, B.H. Ebel, T.W. Koerber, and E.P. Merkel. 1980. Cone and Seed Insects of North American Conifers. Canadian Forestry Service. 122 pp.

Pine Coneworm

Blake, E.A., M.R. Wagner, and T.W. Koerber. 1985. Insects destructive to the ponderosa pine cone crops in northern Arizona. In:Proc. Conifer Tree Seed in the Inland Mountain West Symposium, Aug. 5-6, Missoula, MT. USDA Forest Service, Intermountain Research Station:238-242.
Schmid, J.M, J.C. Mitchell, K.D. Carlin, and M.R. Wagner. 1984. Insect damage, cone dimensions, and seed production in crown levels of ponderosa pine. Great Basin Naturalist:575-578.

Bud and Shoot Insects

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Holsten, E.H., P.E. Hennon, L. Trummer, and M. Schultz. 2001. Insects and Diseases of Alaskan Forests. USDA Forest Service, Alaska Region, R10-TP-87. 242 pp.
Jennings, D.T. and R.E. Stevens. 1982. Southwestern pine tip moth. USDA Forest Service, Forest Insect and Disease Leaflet 58. 7 pp.
Wagner, M.R. 2001. Insects and diseases of southwestern forests. Lecture notes compiled by Michael R. Wagner, Northern Arizona University. 159 pp.

Bark Moths & Pitch Moth

Cain, R., and D. Parker. 1998. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 50 pp.

Western Pine Shoot Borer

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Sower, L.L., G.E. Daterman, and C. Sartwell. 1989. Biology and impact of western pine shoot borer, Eucosma sonomana, in the western United States. p. 102-109. In:Proceedings of the IUFRO working group on Insects Affecting Reforestation, XVIII International Congress of Entomology, 1988. Vancouver, British Columbia, Canada.
Stevens, R.E. and D.T. Jennings. 1977. Western pine shoot borer: A threat to intensive management of ponderosa pine in the Rocky Mountain area and the Southwest. USDA Forest Service, GTR-RM 45. 8 pp.

Pine Tip Moths

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Jennings, D.T. and R.E. Stevens. 1982. Southwestern pine tip moth. USDA Forest Service, Forest Insect and Disease Leaflet 58. 7 pp.

Pinyon and Ponderosa Pitch Nodule Moth

Cain, R., and D. Parker. 1998. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 50 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Ponderosa Pine Seedworm

Hedlin, A.F., H.O. Yates, D.C. Tovar, B.H. Ebel, T.W. Koerber, and E.P. Merkel. 1980. Cone and Seed Insects of North American Conifers. Canadian Forestry Service. 122 pp.

Juniper Twig Pruner

Cain, R., and D. Parker. 1998. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 50 pp.
Itami, J.K. and T.P. Craig. 1989. Life history of Styloxus bicolor (Coleoptera:Cerambycidae) on Juniperus monosperma in northern Arizona. Annals of the Entomological Society of America 82:582-587.

Hardwood Leaf Diseases

Black Leaf Spot

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Shepard's Crook

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Elytroderma Needle Cast

Childs, T.W., K.R. Shea, and K.L. Stewart. 1971. Elytroderma disease of ponderosa pine. USDA Forest Service. Forest Pest Leaflet 42. 6 pp.
Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Scharpf, R.F., and R.V. Bega. 1981. Elytroderma disease reduces growth and vigor, increases mortality of jeffery pines at Lake Tahoe Basin, California. USDA Forest Service. PSW-155. 6 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Ink Spot Leaf Blight

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.

Lophodermella Needle Cast

Millar, C.S. 1984. Lophodermella species on pines. p. 45-55. In:Recent Research on Conifer Needle Diseases. Ed. Glenn W. Peterson. USDA Forest Service, General Technical Report GTR-WO 50.
Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Piñon Needle Rust

Van Arsdel, E.P., and B.W. Geils. 2004. The Ribes of Colorado and New Mexico and their rust fungi. FHTET-04-13. Fort Collins, CO:USDA Forest Service, Forest Health Technology Enterprise Team. 32 pp.

Red Band Needle Blight

Peterson, Glenn W. 1982. Dothistroma needle blight of pines. USDA Forest Service. Forest Pest Leaflet 143. 6 pp.
Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Rhabdocline Needle Cast

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Melampsora Rust

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Sycamore Anthracnose

Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

True Fir Needle Cast

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

White Pine Needle Cast

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Fungi

Atropellis Canker

Tainter, F.H. and F.A. Baker. 1996. Principles of Forest Pathology. John Wiley & Sons, Inc. 805 pp.

Black Canker

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Hinds, T.E. and M.G. Ryan. 1985. Expansion of sooty-bark and ceratocystis cankers on aspen. Plant Disease 69:842-844.
Johnson, D.W., J.S. Beatty, and T.E. Hinds. 1995. Cankers on western quaking aspen. USDA Forest Service, Forest Pest Leaflet 152. 9 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Blue Stain Fungi

Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Tainter, F.H. and F.A. Baker. 1996. Principles of Forest Pathology. John Wiley & Sons, Inc. 805 pp.

Canker Rot of Oak

Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Oak Heartrot Fungi

Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Hypoxylon Canker

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Johnson, D.W., J.S. Beatty, and T.E. Hinds. 1995. Cankers on western quaking aspen. USDA Forest Service, Forest Pest Leaflet 152. 9 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Indian Paint Fungus

Filip, G.M., and Schmitt, C.L. 1990. RX for Abies:silvicultural options for diseased firs in Oregon and Washington. USDA Forest Service, GTR-PNW-252. 34 pp.
Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Tainter, F.H. and F.A. Baker. 1996. Principles of Forest Pathology. John Wiley & Sons, Inc. 805 pp.

Pouch Fungus

Borden, J.H., and M. McClaren. 1970. Biology of Cryptoporus volvatus (Peck) Shear (Agaricales, Polyporaceae) in southwestern British Columbia:distribution, host species, and relationship with subcortical insects. Syesis, Vol. 3:145ï¿½ 154.
Gilbertson, R.L. 1974. Fungi That Decay Ponderosa Pine. Tucson:University of Arizona Press. 197 pp.
Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.

Red Rot

Gilbertson, R.L. 1974. Fungi That Decay Ponderosa Pine. Tucson:University of Arizona Press. 197 pp.
Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.
Lightle, P.C. and S.R. Andrews. 1968. Red rot in residual ponderosa pine stands on the Navajo Indian Reservation. USDA Forest Service, Rocky Mountain Research Station. Res. Pap. RM-37. 12 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Red Belt Fungus

Gilbertson, R.L. 1974. Fungi That Decay Ponderosa Pine. Tucson:University of Arizona Press. 197 pp.
Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Red Ring Rot

Gilbertson, R.L. 1974. Fungi That Decay Ponderosa Pine. Tucson:University of Arizona Press. 197 pp.
Gilbertson, R.L., and L. Ryvarden. 1987. North American Polypores, Volume 2. Oslo:Fungiflora:434-885.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Sooty Bark Canker

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Hinds, T.E. and M.G. Ryan. 1985. Expansion of sooty-bark and ceratocystis cankers on aspen. Plant Disease 69:842-844.
Johnson, D.W., J.S. Beatty, and T.E. Hinds. 1995. Cankers on western quaking aspen. USDA Forest Service, Forest Pest Leaflet 152. 9 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Insect Defoliators

Western Spruce Budworm

Fellin, D.G. and J.E. Dewey. 1982. Western spruce budworm. USDA Forest Service, Forest Insect and Disease Leaflet 53. 10 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

New Mexico Fir Looper

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Alder Flea Beetle

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Johnson W.T. and H.H. Lyon, 1988. Insects that feed on trees and shrubs, 2nd ed. Cornell University Press, Ithaca, NY. 556 pp.

Forest Insect Defoliators

Holsten, E.H., P.E. Hennon, L. Trummer, and M. Schultz. 2001. Insects and Diseases of Alaskan Forests. USDA Forest Service, Alaska Region, R10-TP-87. 242 pp.
McMillin, J.D., and M.R. Wagner. 1989. Assessing the impacts of foliage-feeding insects on timber and scenic beauty of ponderosa pine:a methodological approach. p. 51-59. In:(A. Tecle, W. W. Covington & R. H. Hamre, tech. coor.) Multiresource Management of Ponderosa Pine Forests. USDA Forest Service GTR RMï¿½185.
Niwa, C.G., R.E. Sandquist and 19 others. 2001. Invertebrates of the Columbia River basin assessment area. (T. M. Quigley, Ed.) Interior Columbia Basin Ecosystem Management Project:Scientific Assessment. USDA Forest Service, General Technical Report PNW-GTR-512, Portland, OR. 74 pp.
Wagner, M.R. 2001. Insects and diseases of southwestern forests. Lecture notes compiled by Michael R. Wagner, Northern Arizona University. 159 pp.

Janet's Looper

Lynch, A.M. and Fitzgibbon, R.A. 2005. Biology and impact of Nepytia janetae in spruce-fir forests in Arizona, USA, submitted for publication.
Rindge, F.H. 1967. A new species of Nepytia from the southern Rocky Mountains. New York Entomological Society LXXV:74-76.

Pine-feeding Needleminers

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Stevens, R.E., J.W. Brewer, and D.T. Jennings. 1978. Life history and habits of Coleotechnites edulicola (Gelechiidas) a pinion needle miner in the Southwest. Journal of the Lepidopterists Society. 32 (2):123-129.

Pandora Moth

Carolin, V.M., and J.A.E. Knopf. 1968. The pandora moth. USDA Forest Service. Forest Pest Leaflet 114, 7 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Schmid, J.M., and D.D. Bennett. 1988. The North Kaibab Pandora Moth Outbreak, 1978-1984. USDA Forest Service, GTR-RM-153, 19 pp.

Pine Butterfly

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Pine Sawflies

Ciesla, W.M. and D.R. Smith. 2011. Diprionid Sawflies on lodgepole and ponderosa pines. USDA Forest Service, Forest Insect and Disease Leaflet 179. 12 pp.
Dunbar, C.S. and M.R. Wagner. 1990. Distribution of ponderosa pine (Pinus ponderosa) feeding sawflies (Hymenoptera:Diprionidae) in the United States and Canada. Entomol. News 101:266-272.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
McGregor, M.D., and L.O. Sandin. 1969. Pinyon sawfly, Neodiprion edulicolis Ross. USDA Forest Service, Forest Insect and Disease Leaflet 117. 10 pp.
McMillin, J.D., G. Hengxiao, M.R. Wagner & X. Long. 1996. Host density and elevation effects on the spatial distribution patterns of pine sawflies in eastern Arizona and southwestern China. Forest Ecology and Management 86:151ï¿½161.
McMillin, J.D. and M.R. Wagner. 1993. Influence of stand characteristics and site quality on sawfly population dynamics. pp. 333-361. In:(M. R. Wagner & K. F. Raffa, eds.) Sawfly Life History Adaptations to Woody Plants. Academic Press, Orlando, FL.

Western Tent Caterpillar

Beatty, J. 1979. Forest insect and disease conditions in the Southwest 1979. USDA Forest Service, Southwestern Region Publication 80-7, 29 pp.
Cranshaw, W., D. Leatherman, W. Jacobi, B. Kondraitieff, and L. Mannix. 2000. Insects and Diseases of Woody Plants of the Central Rockies. Bulletin 506A. Colorado State University Cooperative Extension. Fort Collins, 283 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Tiger Moth

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
USDA Forest Service. 1986. Tiger moth. USDA Forest Service, Southwestern Region, Fact Sheet. 2 pp.

Large Aspen Tortrix

Beckwith, Roy C. 1973. The large aspen tortrix. USDA Forest Service, Forest Pest Leaflet 139. 5 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Douglas-fir Tussock Moth

Cain, R., and D. Parker. 1998. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 50 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Wickman, B.E., R.R. Mason, and G.C. Trostle. 1981. Douglas-fir tussock moth. USDA Forest Service, Forest Insect and Disease Leaflet 86. 10 pp.

Fall Webworm

Cranshaw, W., D. Leatherman, W. Jacobi, B. Kondraitieff, and L. Mannix. 2000. Insects and Diseases of Woody Plants of the Central Rockies. Bulletin 506A. Colorado State University Cooperative Extension. Fort Collins, 283 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

White Fir Needleminer

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Tainter, F.H. and F.A. Baker. 1996. Principles of Forest Pathology. John Wiley & Sons, Inc. 805 pp.

Mistletoes

Dwarf Mistletoes

Conklin, D.A., and M.L. Fairweather. 2010. Dwarf mistletoes and their management in the Southwest. USDA Forest Service, Southwestern Region, Forestry and Forest Health, R3-FH-10-01. 23 pp.
Hawksworth, F.G. 1961. Dwarf mistletoe of ponderosa pine in the Southwest. Tech. Bull. 1246. USDA, Forest Service, Rocky Mountain Forest and Range Experiment Station. 13 pp.
Hawksworth, F.G., and B.W. Geils. 1990. How long do mistletoe-infected ponderosa pines live? Western Journal of Applied Forestry. 5 (2):47-48.
Parmeter, J.R., Jr. 1978. Forest stand dynamics and ecological factors in relation to dwarf mistletoe spread, impact, and control. p. 16-30. In:Proceedings of the Symposium on Dwarf Mistletoe Control Through Forest Management. Robert F. Scharpf and John R. Parmeter, Jr., Tech. Coords., April 11-13, 1978, Berkeley, CA:USDA Forest Service, General Technical Report PSW-31. 190 pp.
Tinnin, R.O. 1984. The effect of dwarf mistletoe on forest community ecology. p. 117-122. In:Frank G. Hawksworth and Robert F. Scharpf, Tech. Coords., Biology of Dwarf Mistletoes:Proceeding of the Symposium,1984. USDA Forest Service, GTR-RM-111.

True Mistletoes

Geils, B.W., J. Cibrian Tovar, and B. Moody, tech. coords. 2002. Mistletoes of North American conifers. Gen. Tech. Rep. RMRS-GTR-98. Ogden, UT:USDA, Forest Service, Rocky Mountain Research Station. 123 pp.
Hawksworth, F.G. and R.F. Scharpf. 1981. Phoradendron on conifers. USDA Forest Service, Forest Pest Leaflet 164. 7 pp.
Scharpf, R.F., and Hawksworth, F.G. 1974. Mistletoes on hardwoods in the United States. USDA Forest Service, Forest Pest Leaflet 147. 7 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Other Causes of Damange

Black Bear

Kanaskie, A., J. Chetock, G. Irwin, D. Overhulser. 1990. Black bear damage to forest trees in northwest Oregon 1988-1989, Pest Management Report 90-1, Oregon Department of Forestry, Salem, OR.
Kimball, B.A., D.L. Nolte, D.L. Griffin, S.M. Dutton and S. Ferguson. 1998. Impacts of live canopy pruning on the chemical constituents of Douglas-fir vascular tissues:implications for black bear tree selection. Forest Ecology and Management. 109 (1-3):51-56.
Smith, A.A. 1992. Identification of Distinguishing Characteristics Around Middens of Mount Graham Red Squirrels. Thesis submitted to the faculty of the School of Renewable Natural Resources, University of Arizona. 78 pp.

Burls

Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Drought

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Frost

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Lightning

Wood, R.E. 1983. Mortality caused by root diseases and associated pests on six national forests in Arizona and New Mexico. USDA Forest Service, Southwestern Region, Albuquerque, New Mexico. R-3 83-13. 31 pp.

Red Belt

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Salt Damage

Bolander, P., ed. 1999. Dust palliative selection and application guide. Project Report. 9977-1207-SDTDC. San Dimas, CA:USDA Forest Service, San Dimas Technology and Development Center. 20 pp.
Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Ungulates

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Shepperd, Wayne D. and Fairweather, M.L. 1994. Impact of large ungulates in restoration of aspen communities in a southwestern ponderosa pine ecosystem. In:Covington, W. Wallace; DeBano, Leonard F.; tech. coords. Sustainable Ecological Systems:Implementing an Ecological Approach to Land Management. 1993 July 12-15; Flagstaff, Arizona. GTR-RM-247. Fort Collins, CO:USDA, Forest Service, Rocky Mountain Forest and Range Experiment Station.

Windthrow

Vasiloff, S. 1997. Microburst prediction and detection. N.O.A.A. Western Region Technical Attachment. No. 97-21. 2 pp.

Winter Injury

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Root Disease

Annosus Root Rot

Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.
Livingston, W.H., A.C. Mangini, H.G. Kinzer, and M.E. Mielke. 1983. Association of root diseases and bark beetles (Coleoptera:Scolytidae) with Pinus ponderosa in New Mexico. Plant Disease 67:674-676.
Maijala, P., T.C. Harrington, and M. Raudaskoski. 2003. A peroxidase gene family and gene tree in Heterobasidion and related genera. Mycologia 95:209-221.
Otrosina, W.J.; Scharpf, R.F., technical coordinators. 1989. Proceedings of the Symposium on Research and Management of Annosus Root Disease (Heterobasidion annosum) in Western North America; April 18-21, 1989; Monterey, CA. Gen. Tech. Rep. PSW-116. Berkeley, CA:Pacific Southwest Forest and Range Experiment Station, USDA Forest Service. 177 pp.
Schmitt, C.L., J.R. Parmeter, and J.T. Kliejunas. 2000. Annosus root disease of western conifers. USDA Forest Service, Forest Pest Leaflet 172. 10 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Wood, R.E. 1983. Mortality caused by root diseases and associated pests on six national forests in Arizona and New Mexico. USDA Forest Service, Southwestern Region, Albuquerque, New Mexico. R-3 83-13. 31 pp.

Black Stain Root Disease

Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agricultural Handbook 521. Washington, DC, USDA Forest Service. 199 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Schweinitzii Root and Butt Rot

Gilbertson, R.L., and L. Ryvarden. 1987. North American Polypores, Volume 2. Oslo:Fungiflora:434-885.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Ganoderma Root Rot

Hinds, T.E. 1985. Diseases. In:DeByle, N.V., Winokur, R.P., eds. Aspen:Ecology and Management in Western United States. Tech. Rep. RM-119. Fort Collins, CO:USDA Forest Service, Rocky Mountain Forest and Range Experiment Station:87-106.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Armillaria or Shoestring Root Rot

Hagle, S.K.; Byler, J.W. 1994. Root diseases and natural disease regimes in forest of western U.S.A. In:Johansson, M. and J. Stenlid, eds. Proceedings of the Eighth International Conference on Root and Butt Rots; 1993 August 9-16; Wik, Sweden and Haikko, Finland. Uppsala, Sweden:Swedish University of Agricultural Sciences:606-617.
Nelson, E.V., M.L. Fairweather, S.M. Ashiglar, J.W. Hanna, and N.B. Klopfenstein. 2013. First report of the armillaria root disease pathogen, Armillaria gallica, on Douglas-fir (Pseudotsuga menziesii) in Arizona. Plant Diseaseï¿½First Lookï¿½ paperï¿½http://dx.doi.org/10.1094/PDIS-04-13-0450-PDNï¿½posted June 6, 3013.
Shaw, C.G., III and G.A. Kile. 1991. Armillaria Root Disease. USDA Forest Service, Agriculture Handbook No. 691. 233 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Williams, R.E., C.G. Shaw, III, P.M. Wargo, and W.H. Sites. 1989. Armillaria Root Disease. USDA Forest Service, Forest Insect and Disease Leaflet 78 (rev.). 8 pp.
Wood, R.E. 1983. Mortality caused by root diseases and associated pests on six national forests in Arizona and New Mexico. USDA Forest Service, Southwestern Region, Albuquerque, New Mexico. R-3 83-13. 31 pp.

Tomentosus Root Disease

Gilbertson, R.L., and L. Ryvarden. 1986. North American Polypores, Volume 1. Oslo:Fungiflora:1- 433.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Tkacz, B.M. 1991. Survival of Inonotus tomentosus in spruce stumps after logging. Plant Disease 75 (8):788-790.
Whitney, R.D. 1977. Polyporus tomentosus root rot of conifers. Forestry Technical Report No. 18. Canadian Forestry Service; 12 pp.

Rust of Pine

Comandra Blister Rust

Gilbertson, R.L., and M. Rosemeyer. 1986. Comandra blister rust on Mondell pine in Arizona. Arizona Plant Pathology, Unnumbered Bulletin. Tucson, AZ; Dept. of Plant Pathology, University of Arizona. 3 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Yohem, K.H., G.B. Cummins, and R.L. Gilbertson. 1985. Revised list and host index of Arizona rust fungi. Mycotaxon. 23 (2):451-468.

Southwestern Cone Rust

Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Yohem, K.H., G.B. Cummins, and R.L. Gilbertson. 1985. Revised list and host index of Arizona rust fungi. Mycotaxon. 23 (2):451-468.

Fir Broom Rust

Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Yohem, K.H., G.B. Cummins, and R.L. Gilbertson. 1985. Revised list and host index of Arizona rust fungi. Mycotaxon. 23 (2):451-468.

Western Gall Rust

Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Yohem, K.H., G.B. Cummins, and R.L. Gilbertson. 1985. Revised list and host index of Arizona rust fungi. Mycotaxon. 23 (2):451-468.

Gymnosporangium Rusts

Peterson, R.S. 1967. Studies of juniper rusts in the West. Madro 19:79-91.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Yohem, K.H., G.B. Cummins, and R.L. Gilbertson. 1985. Revised list and host index of Arizona rust fungi. Mycotaxon. 23 (2):451-468.

Limb Rust

Peterson, R.S. 1968. Limb rust of pine:the causal fungi. Phytopathology 58:309-315.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.
Yohem, K.H., G.B. Cummins, and R.L. Gilbertson. 1985. Revised list and host index of Arizona rust fungi. Mycotaxon. 23 (2):451-468.

White Pine Blister Rust

Geils, B.W.; Conklin, D.A.; Van Arsdel, E.P. 1999. A preliminary hazard model of white pine blister rust for the Sacramento Ranger District, Lincoln National Forest. USDA Forest Service, RMRS-RN-6. 6 pp.
Mielke, J.L. 1943. White pine blister rust in western North America. Yale Univ. School of Forestry. Bulletin No. 52. 155 pp.
Sinclair, W.A. and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd ed. Cornell University Press. Ithica, NY. 660 pp.

Sap Suckers

Aphids

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Spruce Aphid

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Pinyon Spindlegall Midge

Cain, R., J. Cota, and C. Ward. 1990. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 48 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Sap-Sucking Insects, Gall Formers and Mites

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Holsten, E.H., P.E. Hennon, L. Trummer, and M. Schultz. 2001. Insects and Diseases of Alaskan Forests. USDA Forest Service, Alaska Region, R10-TP-87. 242 pp.

Pine Needle Scale

Cain, R., J. Cota, and C. Ward. 1990. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 48 pp.
Hagle, S.K., S. Tunnock, K.E. Gibson, and C.J. Gilligan. 1987. Field Guide to Diseases and Insect Pests of Idaho and Montana Forests. USDA Forest Service, Northern Region. 123 pp.

Prescott Scale

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
McCambridge, W.F. 1974. Pinyon needle scale. USDA Forest Service, Forest Insect and Disease Leaflet 148. 3 pp.
McKenzie, H.L., L.S. Gill, D.E. Ellis. 1948. The Prescott scale (Matsucoccus vexillorum) and associated organisms that cause flagging injury to ponderosa pine in the southwest. Journal of Agricultural Research 76:33-51.

Gouty Pitch Midge

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Johnson W.T. and H.H. Lyon, 1988. Insects that feed on trees and shrubs, 2nd ed. Cornell University Press, Ithaca, NY. 556 pp.

Spider Mites

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Johnson W.T. and H.H. Lyon, 1988. Insects that feed on trees and shrubs, 2nd ed. Cornell University Press, Ithaca, NY. 556 pp.

Spittlebugs

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Spruce Aphid

Lynch, A.M. 2003. Spruce aphid in high elevation habitats in the Southwest. pp. 60-63. In:S. L. C. Gosbroke, K.W. Gottschalk, editors, Proceedings of the USDA interagency research forum on gypsy moth and other invasive species, 2002. USDA Forest Service, GTR-NE-300.
Lynch, A.M. 2004. Fate and characteristics of Picea damaged by Elatobium abietinum (Walker) (Homoptera:Aphididae) in the White Mountains of Arizona. Western North American Naturalist. 7-17.
Lynch, A.M., J.L. Wilson, and M.S. Frank. In press. Elatobium abietinum (Walker) populations reach epidemic levels on Picea engelmannii Parry in the interior southwestern United States. Journal of Agricultural and Forest Entomology.
Wilson, J.L. and A.M. Lynch. 1998. Spruce aphid in the Southwest. USDA Forest Service, Southwestern Region.

Oystershell Scale

Cranshaw, W.S, 2013. Oystershell scale fact sheet no.5.513 Colorado State University Extension, Fort Collins.
Crouch C.D., Grady A.M., Wilhelmi N.P., Hofstetter R.W., Depinte D.E., Waring K.M. 2021. Oystershell scale: an emerging invasive threat to aspen in the southwestern US. Biol Invasions, 23:2893-2912.
Grady, A.M.; Crouch, C.D.; Wilhelmi, N.P.; Hofstetter, R.W.; Waring, K.M. 2022. Oystershell Scale: an invasive threat to aspen conservation. Western Aspen Alliance, Utah State University, Logan, Utah, Brief #8. 2 p.

Wood Insects

Ambrosia Beetles

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Hagle, S.K., S. Tunnock, K.E. Gibson, and C.J. Gilligan. 1987. Field Guide to Diseases and Insect Pests of Idaho and Montana Forests. USDA Forest Service, Northern Region. 123 pp.

Carpenter Ants

Coulson, R.N. and J.A. Witter. 1984. Forest Entomology:Ecology and Management. John Wiley & Sons, New York, NY. 669 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Cedar and Cypress Bark Beetles

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Schalau, J. 2003. Cypress bark beetles. The University of Arizona College of Agriculture and Life Sciences Publication AZ1316. 2 pp.

Douglas-fir Beetle

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Schmitz, R.F. and Gibson, K.E. 1996. Douglas-fir beetle. USDA Forest Service, Forest Insect and Disease Leaflet 5. 8 pp.

Pine Engravers

Furniss, R.L. and J.B. Johnson. 2002. Field Guide to the Bark Beetles of Idaho and Adjacent Regions. University of Idaho. 125 pp.
Kegley, S.J., R.L. Livingston, and K.E. Gibson. 1997. Pine engraver, Ips pini (Say), in the western United States. USDA Forest Service, Forest Insect and Disease Leaflet 122. 7 pp.
Livingston, R.L. 1979. The pine engraver beetle in Idaho, life history, habits and management recommendations. Idaho Department of Lands, Forest Insect and Disease Control Report 79-3. 7 pp.
Massey, C.L., and D.L. Parker. 1981. Arizona five-spined ips. USDA Forest Service, Forest Insect and Disease Leaflet 116. 6 pp.
Parker, D.L. 1991. Integrated pest management guide:Arizona five-spined ips, Ips lecontei Swaine, and pine engraver, Ips pini (Say), in ponderosa pine. USDA Forest Service, Southwestern Region, 91-8. 17 pp.

Fir Engraver

Beatty, J. 1979. Forest insect and disease conditions in the Southwest 1979. USDA Forest Service, Southwestern Region Publication 80-7, 29 pp.
Fellin, D.G. and J.E. Dewey. 1982. Western spruce budworm. USDA Forest Service, Forest Insect and Disease Leaflet 53. 10 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Insects of Wood Products

Coulson, R.N. and J.A. Witter. 1984. Forest Entomology:Ecology and Management. John Wiley & Sons, New York, NY. 669 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Juniper Borers

Cain, R., and D. Parker. 1998. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 50 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Mountain Pine Beetle

Amman, G.D., M.D. McGregor, and R.E. Dolph, Jr. 1985. Mountain pine beetle. USDA Forest Service, Forest Insect and Disease Leaflet 2. 11 pp.
Parker, D.L. 1980. Mountain pine beetle, Dendroctonus ponderosae Hopkins, in ponderosa pine, Kaibab Plateau, Arizona. USDA Forest Service, Southwestern Region, Integrated Pest Management Guide 80-8. 12 pp.

Red Turpentine Beetle

Barr, B.A., D.L. Hanson, and C.S. Koehler. 1978. Red turpentine beetle, a pest of pines. University of California, Division of Agricultural Sciences Leaflet 21055. 4 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Smith, R.H. Red turpentine beetle. USDA Forest Service, Forest Insect and Disease Leaflet 55. 9 pp.

Roundheaded Pine Beetle

Cain, R., J. Cota, and C. Ward. 1990. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 48 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
Massey, C.L., Lucht, D.D., and J.M. Schmid. 1977. Roundheaded pine beetle. USDA Forest Service, Forest Insect and Disease Leaflet 155. 8 pp.

Southern Pine Beetle and Mexican Pine Beetle

USDA Forest Service. 1985. Insects and diseases of trees in the South. USDA Forest Service, GTR-R8-5. 98 pp.

Spruce Beetle

Holsten, E.H., R.W. Their, A.S. Munson, and K.E. Gibson. 1999. The spruce beetle. USDA Forest Service, Forest Insect & Disease Leaflet 127. 12 pp.
Schmid, J.M. and R.H. Frye. 1977. Spruce beetle in the Rockies. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, General Technical Report RM-49. 38 pp.

Termites

Coulson, R.N. and J.A. Witter. 1984. Forest Entomology:Ecology and Management. John Wiley & Sons, New York, NY. 669 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Twig Beetles

Cain, R., and D. Parker. 1998. Conifer pests in New Mexico. Rev. ed. (Albuquerque, NM):USDA Forest Service, Southwestern Region. 50 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Western Balsam Bark Beetle

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.
McMillin, J.D., K.E. Allen, D.F. Long, J.L. Harris and J.F. Negron. 2003. Effects of western balsam bark beetle on spruce-fir forests of north-central Wyoming. Western Journal of Applied Forestry 18:259-266.
Wood, S.L. 1982. The bark and ambrosia beetles of North and Central America (Coleoptera:Scolytidae), a taxonomic monograph. Great Basin Naturalist Memoirs. Number 6. 1,359 pp.

Western Pine Beetle

DeMars, Jr., C.J., and B.H. Roettgering. 1982. Western pine beetle. USDA Forest Service, Forest Insect and Disease Leaflet 1. 8 pp.
Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Roundhead borers, Flathead borers

Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA Forest Service, Miscellaneous Publication No. 1339. 654 pp.

Key Contacts

Joel McMillin
Forest Health AZ Zone Leader
Andy Graves
Forest Health NM Zone Leader
Janet Nickerman
R3 Pesticide / Invasive Species Specialist

Email the Forest Health Staff

https://www.fs.usda.gov/detail/r3/forest-grasslandhealth/?cid=FSEPRD1089183

Field Guide to Insects and Diseases

Southwestern Region Field Guide

Field Guide to Insects & Diseases of Arizona and New Mexico

Guide to Forest Insects and Diseases

Damage confined to leaves, buds and shoots

Damage primarily on cones and seeds

Damage confined to branches and stems

Damage confined to roots and lower stem

Navigating the Field Guide Visual Catalog

Animal Damage

Identifying Animal Damage

Black Bears

Porcupines and Squirrels

Ungulates

Sapsucker

Bark Beetles

Southwestern Pine Beetle

Scientific Name (s)

Host

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Pine Engravers

Scientific Name (s)

Hosts

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Mountain Pine Beetle

Scientific Name (s)

Hosts

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Roundheaded Pine Beetle

Scientific Name (s)

Host

Symptoms/Signs

Biology

Effects

Similar Insects

Southern Pine Beetle and Mexican Pine Beetle

Scientific Name (s)

Hosts

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Red Turpentine Beetle

Scientific Name (s)

Hosts

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Spruce Beetle

Scientific Name (s)

Hosts

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Douglas-fir Beetle

Scientific Name (s)

Host

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Western Balsam Bark Beetle

Scientific Name (s)

Host

Symptoms/Signs

Biology

Effects

Similar Insects and Diseases

Fir Engraver