Hemlock Wooley Adelgid Identified in Huron-Manistee National Forests

Release Date: 

Contact(s): Debra-Ann Brabazon, (231) 590-7004


Treatments are planned to be completed this summer.

A Hemlock Wooley Adelgid on a tree leaf.

Hemlock woolly adelgids are small insects that use their long, siphoning mouthpart to extract sap from hemlock trees. They can be easily spotted as they produce small sacks that look like balls of cotton and may appear alone or in clusters under hemlock branches. Feeding weakens needles, shoots and branches of hemlock trees. These insects have the potential to cause significant harm to Michigan’s hemlock population. Photo courtesy of Lorraine Graney, Bartlett Tree Experts. 

 

CADILLAC, Mich., March 13, 2024 - The Huron-Manistee National Forests (HMNFs) recently verified the detection of invasive hemlock woolly adelgid (HWA) at Hamlin Lake on January 31 and the Nordhouse Dunes Wilderness Area on February 2, both in Grant Township, Mason County. This detection makes it the first confirmed infestations on a National Forest in Michigan.  

“We used positive sensitive environmental DNA (eDNA) trap locations to focus our detection survey efforts,” said Forest Silviculturist Carol Young. The eDNA trap captures DNA released by organisms through dead cells, feces, mucus, etc. into the environment.  

Young noted that eleven detections were made on the HMNFs. “We visually confirmed and verified the HWA presence.” Previous HWA detections have been found in Allegan, Benzie, Mason, Muskegon, Oceana, Ottawa and most recently Antrim counties, all within five miles of the Lake Michigan shoreline. 

According to Young, the USDA Forest Service is finishing its visual detection surveys for the year. Foresters are starting to collect and document information within 800 feet of each infested tree. “These delimitation surveys are used to set up a perimeter to determine how many trees are at risk of being infected. This helps us to create a treatment plan,” explained Young, adding that tree size determines the treatment methods and the application rates used.  

Trees in the wilderness will be treated with Imidacloprid tree injections. Imidacloprid is an insecticide that was made to mimic nicotine. Nicotine is naturally found in many plants, including tobacco and is toxic to insects. Imidacloprid is used to control sucking insects, termites, some soil insects and fleas on pets. “Treatment will start late spring and continue through mid-summer,” Young said. She does not believe treatments will impact recreation, because the treatment is not topical, but rather internal to the tree.  

Hemlock woolly adelgids are small insects. In the fall and winter, the adelgids cover themselves with a white, waxy coating for protection appearing as wool bundles the size of a pinhead at the base of hemlock needles. Infestations are recognizable by the appearance of tiny "cotton balls" at the base of hemlock needles on the underside of the branch. Using their long, siphoning mouthparts, HWAs extract sap from hemlock trees, thereby weakening the tree. Over time, tree growth slows and trees take on a grayish-green appearance. Without treatment, infested trees die within four to ten years. 

Although these tiny insects don’t move far on their own, they can be blown by wind or hitchhike on people, recreational equipment, birds or mammals that encounter an infested branch. In a similar way, cars, boats, or RVs parked under infested trees may be able to transport the insects to new locations.  

It is recommended that forest visitors take steps to prevent the spread of invasive species, steps include: 

  • Leaving firewood at home and buying it where you burn it. 
  • Staying on trails to protect natural areas. 
  • Parking in open, paved areas, not in fields or under trees. 
  • Washing your vehicle and recreation equipment often when travelling between areas in the region. 
  • Cleaning gear and vehicles before hitting the road. 
  • Learning to identify Eastern HWA and report it using the directions below. 

These insects are considered invasive because they are not native to Michigan and can cause significant harm to the state’s hemlock resource, estimated at 170 million trees. 

Hemlock trees are common throughout the region. These trees provide food, shade, and cover for many species of birds and mammals especially important during the spring before other plants have grown back their leaves. Eastern hemlock trees often grow around freshwater rivers and streams. In these areas, their shallow roots help to stabilize the soil and limit erosion. The shade also keeps water temperatures cool for animals like fish and aquatic invertebrates. 

Residents in Mason and Manistee Counties are encouraged to carefully examine their hemlock trees for HWA and if found, report it using one of the methods at the end of this article. Infestations are recognizable by the appearance of tiny "cotton balls" at the base of hemlock needles on the underside of the branch. 

Trees infested with HWA should be reported by one of the following means: 

  • Email the Michigan Department of Agriculture and Rural Development at MDA-Info@Michigan.gov. 
  • Call the MDARD Customer Service Center at 800-292-3939. 
  • Use the Midwest Invasive Species Information Network online reporting tool. 
  • Download the MISIN smartphone app and report from your phone. 
  • Be prepared to report the location of infested trees and, whenever possible, take one or two pictures of infested branches to help confirm identification. To avoid spreading hemlock woolly adelgid, do not collect sample branches or twigs. 

The MISIN smartphone app will take a GPS location point if a report is made at the site; it also will allow you to upload photos with a report. 

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A map showing the locations of confirmed Hemlock Wooley Adelgid.

The USDA Forest Service has identified eleven confirmed cases of Hemlock Woolly Adelgid (HWA) in the Huron-Manistee National Forests, impacting hemlock stands in the Nordhouse Dunes Wilderness Area and near Hamlin Lake. Previous HWA detections have been found in Allegan, Benzie, Mason, Muskegon, Oceana, Ottawa and most recently Antrim counties, all within five miles of the Lake Michigan shoreline. Graphic courtesy of the USDA Forest Service.  


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