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Why state officials want you to look for this tree-killing insect

Jan 10, 2017

State officials want you to check your trees for a tiny insect. It’s called the hemlock woolly adelgid, and it survives by sucking sap from hemlock trees.

This insect was first detected in Michigan in 2006.

Roger Mech is a forest health specialist with the Michigan Department of Natural Resources. He says although the insects have been seen here before, there are now a few more reasons to worry.

“Our biggest concern now are detections that were made in 2015 over in Muskegon and Ottawa County on the west central side of the Lower Peninsula. Our concern there is that unlike these other isolated detections, this one is appearing to be much wider spread," he says. "The other concern is that we’re finding for the first time hemlock trees that have been killed by hemlock woolly adelgid.”

From the DNR:

These tiny insects secrete white wax as they feed on sap from hemlock shoots and branches. Hemlock woolly adelgid (HWA) feeding can kill needles, shoots and branches. Over time, growth slows as trees become less vigorous and trees may take on a grayish-green appearance. Infested hemlocks, especially large, old trees, are often killed when other stress factors, such as drought, affect trees.

In order to slow the spread of the insect, the Michigan Department of Agriculture and Rural Development is considering a quarantine within the state. Officials want to restrict the movement of things like hemlock nursery stock, and firewood.

Mech says that he’s hopeful about the effectiveness of the move.

“This internal quarantine that is now under review is focusing on the Muskegon and Ottawa County areas. And when that is put in place, hopefully sometime early this year, that will go a long way to prevent movement of infested trees and infested branches and so forth from the infested areas into areas that currently do not have hemlock woolly adelgid.”

Finding the hemlock woolly adelgid

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What should people look for if they have hemlock trees?

Hemlock woolly adelgid nymphs in dormancy.
Credit USDA

“This time of year, what you’re going to see is the adult stage. The adult produces white, wooly wax as a means of protecting itself from weather and from predators. And so if you were to look on the underside of hemlock branches, you’ll see this white, fuzzy wool substance there, and that can be hemlock woolly adelgid,” says Mech.

Some things could be mistaken for evidence of hemlock woolly adelgid - spider webs, for instance.

But if you think your hemlock tree could be infested, state officials want you to let them know.