• Invasive hemlock woolly adelgid has been found in Huron-Manistee National Forests.
• It's the latest in a concerning string of sightings as the insect moves north — where most of Michigan's hemlock trees are.
• Officials say they can treat trees and areas already affected, but all-out prevention is difficult: "There is a good chance that a lot of hemlocks will die."
A small, invasive species has slowly been marching northward through Michigan.
The aphid-like insects — called hemlock woolly adelgid — were found in Huron-Manistee National Forests this week. Officials say it’s the first confirmed detection of the species in Michigan’s national forests.
The insect has, for the most part, been confined to southern Michigan for several years. But it’s slowly creeping north – where most of the state’s hemlock trees are.
Earlier this month, a portion of Sleeping Bear Dunes National Lakeshore was closed to treat a site with a hemlock woolly adelgid infestation.
Audrey Menninga is director of the Northwest Michigan Invasive Species Network. She says treatment with pesticides is usually reserved for trees that already have an infestation and their surrounding areas. But it will be difficult to fully prevent future infestations.
“As we move further north, there’s just so many hemlocks that we don’t have enough people, or time, or management ability to save every single hemlock. And there is a good chance that a lot of hemlocks will die,” Menninga said.
Hemlocks play a critical role in northern Michigan’s ecosystems: providing shelter for birds and deer as well as helping keep streams cold for fish. The trees are also important for the state’s timber industry.
Officials say they will treat the infected trees near Hamlin Lake and Nordhouse Dunes, plus the surrounding areas.
Hemlock woolly adelgids are particularly easy to spot in the fall and winter. That’s because the insects cover themselves in a white, cottony ball of wax at the base of hemlock needles to lay eggs. The white ovisacs often have a wool-like appearance – similar to the tip of a cotton swab – making them easily identifiable in November through July.
As the adelgids feed, they suck sap from the new growth on hemlock trees, killing needles. Without pesticide treatment, an infestation can cause a hemlock tree to die in four to 10 years.
Menninga, with the Northwest Michigan Invasive Species Network, says there are a few key ways to prevent the species’ spread.
“If you have hemlocks overhanging driveways or anywhere a person or a vehicle could brush against, we recommend that people trim [the trees] up to about 16 feet – that will clear a delivery truck that’s coming,” she said.
In addition to cars and people, birds also spread hemlock woolly adelgid.
“If you have bird feeders at your house, try to move them away from hemlocks just to encourage birds not to congregate in the hemlock trees,” Menninga said.
Learn more about how to identify hemlock woolly adelgid here. For courses on how to identify different “watch list” invasive species in Michigan, visit the Midwest Invasive Species Network. To report a suspected infestation of hemlock woolly adelgid, email MDA-Info@michigan.gov or use this online reporting tool.
