Conifer Stem Decays

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

Ganoderma applanatum (Pers.) Pat.

Of 13 observations of Ganoderma applanatum made during ground detection surveys in 2023, seven were on western hemlock and two on red alder in Southeast Alaska, while the remaining observations were on balsam poplar and Alaska birch in Southcentral and Interior Alaska. Twenty-seven research grade observations were contributed through iNaturalist from the same general locations but also near Talkeetna and the Kenai Peninsula. Ganoderma applanatum is likely a species complex, found on both hardwoods and conifers in coastal Alaska. On hardwoods in Southeast Alaska, the conk tends to be thinner and has a paler upper surface without the abundant dusting of brown spores.  

Click the conk image to view full Ganoderma applanatum album on Flickr. 

Hosts: Mainly hardwoods; but sometimes western and mountain hemlock, and white and Sitka spruce. Identification: Perennial, woody, fan- or shelf-shaped conk. Usually occurs as a saprobe on decaying logs and stumps. Occasionally found as a heart rot on wounds of living trees. Top: dull, dusty brown to grey-brown with concentric ridges. Bottom: white pore surface that immediately browns when touched. Interior: dark brown to cinnamon. Damage: Spongy mottled white rot of sapwood and heartwood. Remarks: Known as the artist’s conk because the fresh pore surface bruises dark brown when touched or scratched. Intricate etchings can be preserved for years if properly dried.

Ganoderma tsugae Murrill  
Ganoderma oregonense Murrill 

While we have been identifying the species of lacquer/varnish conk, which occurs on hemlock in Alaska, as Ganoderma tsugae, a likely alternative is Ganoderma oregonense (Loyd et al. 2018, PLoS ONE 13(7): e0199738. https://doi.org/10.1371/journal.pone.0199738). Based on spore size, we identified three dried specimens collected in Juneau and one along Behm Canal on Revillagigedo Island as G. oregonense. Though we did not detect varnish conk during ground detection surveys this year, ten research grade observations were contributed via iNaturalist between Hoonah and Ketchikan in Southeast Alaska. This fungus tends to occur on dead wood and appears to be more common in southern parts of the Panhandle.. 

Click the image to view full Ganoderma tsugae album on Flickr. 

Hosts: Western hemlock; occasionally other conifers. Identification: Annual, shelf or fan-shaped conk. Usually saprobic on large, old stumps or logs. Top: surface distinctly varnish-like and shiny reddish brown, at first knobby or elongated becoming somewhat fan-shaped. Bottom: white pore surface, becoming brownish with age. Usually bruises brown. Pores minute. Stalk: lateral (from side), varnished reddish brown, sometimes absent. Damage: White rot decay appears wet, spongy, soft, straw-colored or white in the butt or stem. May have large black spots scattered throughout. Remarks: Also called lacquer conk, this fungus has long been used in traditional medicine; modern research has shown potential medicinal benefits, including wound healing and anti-tumor activity in mice.

Laetiporus conifericola Burds. & Banik

In Alaska, Laetiporus conifericola causes brown cubical rot of conifers, primarily spruce and hemlock in coastal Southeast and Southcentral Alaska. Eight observations were made on Prince of Wales and northeastern Chichagof Island during ground detection surveys in 2023, while 86 research grade observations were recorded in iNaturalist spanning coastal Alaska from Ketchikan to Kodiak Island and Katmai National Park. The iNaturalist application can be particularly helpful in cataloging the occurrence of popular, easily identified fungi, like the sulfur fungus, with ephemeral fruiting structures.

Click the image to view full Laetiporus conifericola album on Flickr.

Hosts: Spruce and hemlock; occasionally shore pine. Identification: Annual, shelving, in clusters, fleshy; usually on lower bole of conifers. Primarily saprobic on dead trees and stumps, but occasionally causes heart rot on living trees. Top: bright orange to yellow when fresh; crumbly white after it dies. Bottom: sulfur-yellow with small pores often in clusters. Inside: Yellow, watery, and soft when fresh; white and chalky or soggy after it dies. Damage: Brown cubical rot, may have white mycelial felts. Remarks: Edible when young, some think the conk tastes like chicken. Also called Sulfur Shelf fungus. The mycelial felts in decayed wood is somewhat similar to that of the quinine conk but do not taste bitter. Use caution when harvesting fungi for consumption.

Laricifomes officinalis (Batsch) Kotl. & Pouzar. (=Fomitopsis officinalis)

Hosts: Spruce (especially Sitka spruce), hemlock, larch, and shore pine. Identification: Rare. Perennial, woody, vaguely hoof-shaped to elongated-columnar conk. Usually occurs high on bole of living old-growth trees, but also persists for many years as a saprobe on dead trees. Top: zoned, white or yellow-white turning to grey or light brown with age, chalky coating, sometimes greenish with algae. Bottom: Convex, white when fresh with tiny round uniform pores, drying to light brown. Inside: white to grey, cheesy to chalky with age, distinctly bitter taste. Damage: Early decay light yellow to red-brown. Advanced decay is a crumbly brown cubical rot. Thick, white, bitter-tasting mycelial felts may form in shrinkage cracks. Remarks: A single fruiting body indicates extensive heart rot and hazard of tree failure. Conks have long been used in traditional medicine and show promise in modern research. Many cultures, including the Tlingit, have carved conks into shaman grave guardians.

Phaeolus schweinitzii (Fr.:Fr.) Pat.

Phaeolus schweinitzii is most common in coastal forests of Southeast Alaska on Sitka spruce but has also been recorded on shore pine and white spruce. In 2023, it was observed on white spruce at one location in Southcentral near Girdwood, and on Sitka spruce at eight locations in Juneau, Gustavus, and the Organized Village of Kasaan in Southeast Alaska. Twenty-seven research grade observations were contributed through iNaturalist in Southeast from Skagway to Prince of Wales Island; in Southcentral Alaska near Girdwood; and in Interior Alaska near Fairbanks. The fruiting bodies are most noticeable when they emerge from broken tree boles or below-ground roots in late summer and fall. Root and lower bole damage can promote infection, an important management consideration at developed recreation sites. This fungus plays an important role in forest success in even-aged spruce forests, including those originating after glacial recession. Bole breakage of large spruce trees varies forest structure and diversity. The decaying wood of freshly snapped trees has a strong pleasant licorice fragrance.

Click the image to view full Phaeolus schweinitzii album on Flickr.

Hosts: Sitka spruce, white spruce, and hemlock; rare on shore pine in Alaska. Identification: Large, annual, layered fruiting body; shelf-like on lower bole; circular and stalked with sunken center on ground. Develops on both live and dead trees/logs. Turns dark red brown and brittle when dead (resembles cow pie). Top: velvety, yellow to orange when young, turning brown with an olive brown to yellowish margin. Bottom: large, irregularly shaped pores, bright yellow to orange when young becoming greenish yellow, olive, or brown; quickly bruises dark brown. Damage: Brown cubical butt rot, often extensive. Rapid loss of tensile strength, even at fairly early stages of decay, may lead to breakage on lower bole. Remarks: Also known as the cow pie fungus, velvet top fungus or dyer’s polypore. Can be used to create yellow, brown, and green dyes. Sometimes confused with Onnia tomentosa.

Phellinus hartigii (Allesch. & Schnabl) Pat.

We recorded Phellinus hartigii on western hemlock at three locations near Juneau and one location on eastern Mitkof Island in 2023. An additional research grade observation was made in Juneau via iNaturalist. This fungus can invade through stem wounds, including bole swellings caused by hemlock dwarf mistletoe. Although infrequently encountered in Southeast Alaska, we have repeatedly observed mortality of infected trees within a decade of initial detection due to disease activity in the sapwood girdling the stem.  

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Click the conk image to view full Phellinus hartigii album on Flickr. 

Hosts: Western and mountain hemlock. Identification: Uncommon. Light brown perennial conk, often occurs on undersides of limbs or branch stubs, also on tree bole; may be velvety and flattened against tree bole. Top: dark brown to black, cracked. Bottom: tan to rusty-brown with very small, uniform pores. The pore layer of the conk may cover a much greater area than the upper surface. Appears velvety when fresh. Inside: yellow- to rusty-brown with streaks of white mycelium. Damage: White rot of the sapwood and heartwood of living trees. Incipient (early) decay appears as irregular patches of brown to purple discoloration. Advanced decay appears bleached and laminated on radial sections with brown zone lines. Decay is usually limited to the area just above and below the conk. Bark may appear sunken around conks when the sapwood is killed. Remarks: Conks are difficult to remove from trees. Hartig’s conk is named after Robert Hartig, a 19th century German forest scientist regarded by many as the father of forest pathology.

Porodaedalea pini (Brot.) Murrill (=Phellinus pini)

Porodaedalea pini was recorded by FHP staff at 16 sites in Southeast Alaska near Juneau, Sitka, Ketchikan, and Prince of Wales Island and at 12 sites near Anchorage, Girdwood, on the Kenai Peninsula near Kenai Lake, and a site on Kodiak Island. One observation was recorded near Fairbanks. Although primarily considered a heart rot, P. pini can progress into sapwood and kill trees. Observations were made on mountain hemlock, western hemlock, Sitka spruce, and white spruce, in decreasing order of incidence. Additionally, 24 research grade observations were recorded in iNaturalist near our observations but also on spruce on Kodiak Island and in Denali Park. Although more common in coastal forests, the range of P. pini extends into Interior Alaska. Multiple fruiting bodies along the length of the tree bole indicate extensive internal decay.  

Click the image to view full Porodaedalea pini album on Flickr.

Hosts: Hemlock, spruce and shore pine; occasionally western redcedar. Identification: Perennial, woody, fan-, shelf-, to hoof-shaped conk. Occurs anywhere on bole of live or recently dead trees. Often associated with branch stubs. Top: reddish brown to dark brown with a narrow, velvety golden margin; usually zoned in concentric rings; becoming furrowed and rough. Bottom: yellowish brown to rusty brown, pores angular to nearly slot-like. Interior: bright rusty brown; corky to woody. Damage: White pocket rot. Incipient (early) decay is a red stain in the heartwood that appears as a well-defined ring in cross-section. In advanced decay, small flecks of fungal mycelium are evident and once-separate areas of decay merge. Remarks: Decay can progress from the heartwood to the sapwood and cause tree death.

Stem decays rot or deteriorate wood, primarily in tree trunks, rather than roots and butts. They can be identified based on the presence and characteristics of conks, mushrooms, or other fungal structures on tree boles, when present. The characteristics of decayed wood and species of host tree can also be helpful for identification. Wildlife holes, cavities, and hollows indicate the presence of stem decay on live trees, even when conks and mushrooms are absent. Heart rot develops primarily in the heartwood (inner wood) of living trees, whereas sap rot develops in the sapwood (outer wood beneath bark) and is usually extensive only in dead trees. Bole wounds and cracks provide entry points for many stem decay fungi, although some decays enter through natural openings like branch stubs.

Brown rots are particularly detrimental to tree strength. They degrade cellulose fibers leaving behind brownish lignin, which dries in brittle cubes. White rots decompose all wood components (cellulose and lignin); wood remains fibrous until very late stages of decay. The color and texture of white rots is dependent upon the causal fungi.

By predisposing large old trees to bole breakage and windthrow, stem decays are key disturbance agents. Individual tree mortality, much of it caused by heart rot fungi, creates small-scale canopy gaps and appears to be the leading form of disturbance in the coastal rainforest (Hennon 1995), where fire and other large-scale disturbances are uncommon. All major tree species in Southeast Alaska have been found killed in this manner. Stem decays influence stand structure and succession, perform essential nutrient cycling functions, increase biodiversity, and enhance wildlife habitat. Heart rot has an obvious and essential role in wood decomposition and has been demonstrated to be a site of nitrogen fixation by other microorganisms. Cavities created by stem decay fungi in standing trees provide crucial habitat for many species (bears, voles, squirrels and birds). Stem decays reduce merchantable timber volume from mature harvest units (especially old-growth) and can be hazardous in managed recreation areas. Many stem decay fungi cause heart rot of living trees, others decay the wood of dead trees, and some grow on dead tissue of both live and dead trees. Most of these decays do not actually interfere with the normal growth and physiological processes of live trees since the vascular system is unaffected. However, some decay pathogens, such as Phellinus hartigii and P. pini may attack the sapwood and cambium of live trees after existing as a heart rot fungus. Many of the fungi that are normally found on dead trees (e.g., Fomitopsis pinicola) can grow on large stem wounds, broken tops and dead tissue of live trees. Root and butt rot fungi can also cause stem decay in the lower bole (e.g., Phaeolus schweinitzii).

Wounds on live trees caused by logging activities are potential sites of infection for decay fungi to cause appreciable timber losses (Wright and Isaac 1956). Generally, larger, deeper wounds and larger diameter breaks in tops result in a faster rate of decay (Hennon 1990). Without logging injury, heart rot in young forests are typically at very low levels until stand age 100 to 150 years. Eventually, heart rot consumes as much or more wood volume annually than is produced by the live trees. There are methods that could be used to promote earlier development of stem decays for wildlife habitat in young-growth stands with non-timber objectives (Filip et al. 2011, Hennon and Mulvey 2014), such as intentional bole wounding and top breakage during stand entries. In some instances, bole breakage can be encouraged to occur in a specific direction (e.g., across steams for coarse woody debris input) by causing wounds to one side of the bole (e.g., the side that faces the stream).

 

Our knowledge of stem decay impacts on timber volume loss primarily come from two cull studies in Southeast Alaska (Kimmey 1956 and Far et al. 1976). A study by Hennon and McClellan (2003) evaluated modes of tree mortality (e.g., died standing, broken bole, uprooting) in old-growth forests. Permanent monitoring plots throughout Southcentral and Interior Alaska (evaluated 2013-2016) are helping to build information about the distribution and relative importance of stem decays on various tree hosts in other regions and forest types in Alaska.

An important cull study conducted by James Kimmey in Southeast Alaska in the 1950s found that brown rots were the most significant source of cull for Sitka spruce, while white rots were most significant for western redcedar (especially Obba/Ceriporiopsis rivulosa and Phellinus weirii) and western hemlock. Farr et al. (1976) found similar high rates of decay in old-growth forests as Kimmey (1956). These and other studies have shown that stem decay incidence and volume increase with tree size. The amount of defect also depends on tree species: for any given size or age class, redcedar was the most defective species, followed by western hemlock and Sitka spruce. Although redcedar wood products are known for decay resistance, it seems that a few species of decay fungi are specialized to overcome the decay resistance of live redcedar but do not affect wood in service.