It’s time to look for signs of the invasive Asian longhorned beetle

The Asian longhorned beetle, or ALB for short, is a non-native, wood-boring beetle considered invasive in North America because it attacks at least 12 types of hardwood trees, including maples, elms, horse chestnuts, birches and willows. There are no predators or diseases in North America 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, creating large, round exit holes approximately 3/8 to 1/2-inch in size.

Why be concerned?

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.

Isolated infestations in several states have caused the removal of thousands of trees in neighborhoods, parks and natural areas.

Although ALB has not yet been discovered in Michigan, it is crucial to look for any potential signs of its presence. Discovering early signs of infestation can prevent widespread damage to the state’s forest resources, urban landscapes and maple syrup production.

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.

Signs that a tree might be infested include:

• 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-laying 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.

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 dull black to bronze in color.
• The brown prionid is a common native longhorned beetle distinguished by its overall brown color and lack of patterns on its wings or antennae.
• The cottonwood borer is about the same size as the Asian longhorned beetle and is also black and white, but 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.

Report signs of ALB

If you think you found a beetle or tree damage, report it by calling the ALB hotline at 1-866-702-9938. Or submit an online report through the ALB web page. Try to photograph the beetle or tree damage. If you can, capture the beetle in a durable container and freeze it. This helps preserve the insect for identification.