LANSING, Mich. — Hemlock woolly adelgid, tiny invasive insects that suck nutrients from hemlock trees, has already been found in five southwest Michigan counties and state officials want residents to check trees for the pests.
They’re known to be present in Allegan, Ottawa, Muskegon, Oceana and Mason counties, according to a news release Monday.
State agency staff, university researchers and regional cooperative invasive species management areas have been working to identify and contain infestations that span across public and private lands.
If untreated, hemlock woolly adelgids can kill hemlock trees in four to 10 years. However, trees can be protected with proper insecticide treatments.
Winter is the ideal time to look for evidence of an infestation, according to Robert Miller, invasive species prevention and response specialist at the Michigan Department of Agriculture and Rural Development.
“Cooler temperatures trigger feeding activity,” Miller said. “As hemlock woolly adelgids feed, they secrete a white, waxy material that creates ovisacs. The presence of these small, round, white masses makes it possible to identify infested trees.”
These insects are considered invasive because they’re not native to the state and cause significant harm to Michigan’s hemlock resource.
State officials say that without pressure from native predators or diseases, populations continue to grow, threatening an estimated 170 hemlocks across the state.
Survey crews will be looking for signs of hemlock woolly adelgid on public and private lands within five miles of the Lake Michigan shoreline, the most probable area for new infestations.
Infested trees and any other eastern hemlocks within the area will be mapped and tagged, then prioritized for summer treatment.
Officials say they’ll seek landowner permission before conducting surveys of hemlocks on private lands.