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Heads up! It's time to check trees for invasive Asian longhorned beetle
August 09, 2022
August is a great time to enjoy the outdoors, and it’s also the best time to spot the invasive Asian longhorned beetle as adults emerge from trees. That’s why the U.S. Department of Agriculture is declaring August as “Tree Check Month.” Checking trees for the beetle and the damage it causes is one way you can protect trees and help the USDA’s efforts to eliminate this beetle from the United States.
The Michigan departments of Agriculture and Rural Development; Environment, Great Lakes, and Energy; and Natural Resources are joining the USDA in asking people to take just 10 minutes this month to check trees around homes for the beetle or any signs of damage.
The Asian longhorned beetle, or ALB for short, is a non-native wood-boring beetle considered invasive in North America because it attacks 12 types of hardwood trees, including maples, elms, horse chestnuts, birches and willows. Here, there are no predators or diseases to keep ALB populations in check. In its larval stage, the insect feeds inside tree trunks and branches during the colder months. The beetle creates tunnels as it feeds, and then it chews its way out as an adult in the warmer months.
Infested trees do not recover and eventually die. They also can become safety hazards since branches can drop and trees can fall, especially during storms.
You can help
Although this invasive beetle has not yet been discovered in Michigan, it is crucial we keep an eye out for it. Discovering early signs of infestation can prevent widespread damage to the state’s forest resources, urban landscapes and maple syrup production.
“We’re asking for the public’s help to find Asian longhorned beetle and any tree damage it causes, because the sooner we know where the insect is, the sooner we can stop its spread,” said Josie Ryan, the USDA Animal and Plant Health Inspection Service’s national operations manager for the ALB Eradication Program. “Five of the 15 known infestation sites in the U.S. were detected and reported by alert residents, including the most recent discovery in Hollywood, South Carolina. This shows how critical public participation can be.”
The USDA recently reported the infestations at 10 of those locations have been eradicated.
Look for signs
Whenever you are outdoors, take time to look at the trees around you for signs of the Asian longhorned beetle, including:
- Round exit holes – about the diameter of a pencil – found in tree trunks and branches.
- Shallow oval or round scars in the bark, where the adult beetle chewed an egg site.
- Material that looks like wood shavings lying on the ground around the tree or in the branches.
- Dead branches or limbs falling from an otherwise healthy-looking tree.
Look for the beetle
Adult Asian longhorned beetles are distinctively large, ranging from 3/4 to 1 1/2 inches in length, not including their long antennae. The beetles are shiny black, with random white blotches or spots, and their antennae have alternating black and white segments. They have six legs that can be black or partly blue, with blue coloration sometimes extending to their feet.
Be aware of look-alikes
Several beetles and bugs native to Michigan often are mistaken for the Asian longhorned beetle, but there are differences to be aware of:
- The white-spotted pine sawyer has a distinctive white spot below the base of its head – between its wings – and is brownish in color.
- The cottonwood borer is about the same size as the Asian longhorned beetle and is also black and white, but it has a pattern of single, broad black stripes down each wing, and its antennae are all dark.
- The northeastern pine sawyer reaches up to 2 inches in length, has very long antennae and is gray in color.
- The eastern eyed click beetle has distinctive eye circles on the back of its head. It rolls over when threatened, then clicks and makes a flipping movement to get back on its feet.
Adults: Adult Asian longhorned beetles emerge from within trees in late summer to mate. Females chew small depressions in tree trunks or branches, such as those seen here, to deposit eggs. Photo courtesy of Kenneth R. Law, USDA APHIS PPQ, Bugwood.org.
Frass: Material resembling wood shavings at the base of a tree or tree branches is a sign of Asian longhorned beetle infestation. Photo courtesy of Kenneth R. Law, USDA APHIS PPQ, Bugwood.org.
Identification: The Asian longhorned beetle is a large, shiny black beetle with irregular white spots and black and white banded antennae. Photo courtesy of USDA APHIS PPQ.
WSPS: The white-spotted pine sawyer is native to Michigan and often mistaken for the Asian longhorned beetle. Look for a white spot between the upper wings to identify this pine sawyer. Photo courtesy of William M. Ciesla, Forest Health Management International, Bugwood.org.
Cottonwood: The cottonwood borer’s antennae are all black. Photo courtesy of Gerald J. Lenhard, Louisiana State University, Bugwood.org.
NEPS: The northeastern pine sawyer is a large beetle reaching 2 inches in length. Its body is primarily gray with white and black spots. Photo courtesy of Jim Brighton.
Eyed beetle: The eastern eyed click beetle is distinguished by large circles on the back of its head. Photo courtesy of iNaturalist./