State says to watch for invasive beetle on Michigan’s doorstep

By: Kevin Bunch | C&G Newspapers | Published August 31, 2015


METRO DETROIT — An invasive, tree-killing insect working its way across the U.S. is closing in on Michigan, and the Department of Natural Resources is asking residents to be watchful.

The Asian longhorn beetle, first found in New York back in 1996, bores into trees to lay its eggs, which then hatch and bore deeper to the heart of the tree, according to DNR spokeswoman Joanne Foreman.

“Basically, there is a very short period where they’re actually beetles and mating, and that’s the late summer,” Foreman said. “Once the female is impregnated, she will drill these dish-like depressions into a tree, deposit one egg into each one, which will then open into a larvae and bore into the tree.”

Those larvae bore so deep into the tree that the pesticidal treatments used for other species, like emerald ash borer, are ineffective. Those larvae then begin eating the tree from the inside, eventually pupating into adult beetles and boring their way back out, Foreman said.

The boreholes are about three-eighths of an inch — big enough to fit a pencil in, she said. And since the beetles do not tend to fly far, the females like to deposit all their eggs on one tree. The collective boring and eating is enough to kill the tree, Foreman said.

The beetle particularly likes maple trees. Foreman said the beetle will infest birch, willow, buckeye, horse chestnut, elm and other hardwood species.

“It’s a significant list of trees they can attack and have been known to attack — that’s what makes this such a bad pest,” Foreman said. “Not only can you lose a species of trees, but you stand to lose several species.”

Researchers have been unable to identify any natural predators for the beetle in its home environment or any local species that are preying on it, she added. As a result, extermination and control is difficult, and quarantine is the order of the day.

Foreman said the Michigan Department of Agriculture and Rural Development would work with the DNR in coming up with specific plans, but typically a plan involves destroying infested trees and monitoring nearby ones for the beetles. People would be banned from moving wood from, to or through the quarantine zone.

The beetle has not been found in Michigan yet, but nearby states like Ohio and Illinois, as well as the province of Ontario, have had Asian longhorn beetle sightings and quarantines.

Michigan is contending with other invasive species right now, though. MDARD spokeswoman Jennifer Holton said hemlock wooly adelgid — a tiny insect that excretes a white wax while feeding on hemlock trees, stressing them and making them prone to dying — is a major area of concern, as is the pathogen thousand cankers disease.

“We are looking for a variety of invasive pests, including the (Asian longhorn) beetle, because early detection will be key to developing a response effort,” Holton said.

Hemlock wooly adelgid is an invasive pest that has popped up several times in the state since 2006, most recently in Ottawa County. Holton said the aphid-like creature uses its long mouth to feast on the sap of hemlock trees.

The adelgid can be controlled with pesticide treatments on trees in the areas where it’s found, though its small size can make it difficult to detect early. The wind, birds and other animals can easily transport the insect elsewhere, and Holton said people are asked not to move hemlock materials to and from areas of concern.

Holton suggested visiting for more information on the adelgid and the Asian longhorn beetle.

If the beetle — or signs of it boring into trees — is found, people are urged to contact MDARD at (800) 292-3939 or email If possible, Foreman said to catch the beetle in a jar and keep it in the freezer, or at least try to get pictures of the tree or beetle itself.

Foreman asked that people do not move wood — whether for firewood or some other purpose — due to it being an easy way for invasive pests to get around.

“You don’t know why the tree died, and you may not recognize what’s wrong, but moving it is a terrible way to transport a lot of tree pests,” Foreman said. “It’s why we had issues with emerald ash borer and gypsy moth, and the beetle is just as easily transportable. Burn it where you buy it, and don’t move firewood.”