Michigan DNR, Eastern Region Team Up on Invasive Insect

branch infested with hemlock woolly adelgid

Caption: Closeup of branch infested with hemlock woolly adelgid. Photo courtesy of the Connecticut Agricultural Experiment Station by Mark McClure.

The Forest Service’s Eastern Region and Michigan Department of Natural Resources (DNR) forest health programs are working together to track the hemlock woolly adelgid, a harmful invasive insect detected in Michigan and edging closer to national forests there.

Hemlock trees across eastern North America are threatened by this serious invasive pest from Japan. The range for eastern hemlock spans from Georgia to Nova Scotia and as far west as western Wisconsin. It is an important native tree species that provides habitat for wildlife and shades streams for fish, plants and other aquatic life. Their roots also stabilize stream banks. It is one of our longest-lived trees, capable of living hundreds of years and reaching very large sizes.

The hemlock woolly adelgid — a small insect, similar to an aphid — kills hemlock trees by the colossal build-up of insects that feed on cells within the tree’s shoots, coupled with the response of the tree to the damage. It spreads by wind, birds, mammals and humans moving plant material, like nursery stock, around.

The Eastern Region partners with state agencies and others across its 20 states and the District of Columbia, providing grant funding and technical assistance on a wide range of forest health issues. A cooperative agreement between the Forest Service’s Forest Health Protection program and Michigan DNR’s Forest Health program has vastly improved their ability to detect hemlock woolly adelgid in Michigan.

Sunny Lucas, from the Forest Service’s Forest Health Protection program, expressed concern that the hemlock woolly adelgid will make its way to the Huron-Manistee National Forests.

“It hasn't been detected there yet, but I fear it is only a matter of time,” Lucas said.  

The cooperative agreement focused a well-trained DNR forest health strike team to search for signs and map out the extent of hemlock woolly adelgid, as well as oak wilt and a heterobasidion root disease, on federal lands in Michigan. The Forest Service initially provided a $100,000 grant for the project in 2018. It was modified last year to provide funds beyond the original amount, and the expiration was extended to Sept. 30, 2021.

Lucas added that Michigan has also formed a hemlock woolly adelgid coordinating committee in response to the threat. State and federal agencies, including the Forest Service, along with several conservation-based nonprofits and Michigan State University, will work together to detect and track the insect.

In addition to parts of western Michigan, hemlock woolly adelgid currently infests eastern hemlocks across much of the eastern United States from Alabama and Georgia to Maine, and into eastern Nova Scotia in Canada.

To detect hemlock woolly adelgid, look at the underside of hemlock foliage for white woolly masses at the base of needles.