Start checking trees for signs of Asian longhorned beetles: What they are, why they’re a threat

Beetle has not been found in Michigan yet

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. (Kenneth R. Law, USDA APHIS PPQ, Bugwood.org.)

Environmental officials want you to start checking your trees for adult Asian longhorned beetles because the invasive beetle starts to emerge this month.

Checking for the beetle and the damage it leaves behind is one way you can protect trees and fight an invasive species. Michigan environmental officials are asking residents to take 10 minutes this month to check trees around their homes.

What is the Asian longhorned beetle (ALB)?

It’s an invasive wood-boring beetle that attacks 12 types of hardwood trees, including maples, elms, horse chestnuts, birches and willows. It doesn’t have any predators or diseases to keep the population down.

When it’s in its larval stage, it feeds inside tree trunks and branches during the colder months. It creates tunnels as it feeds and then chews its way out as an adult in the warmer months.

Trees that have been invested will not survive.

“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.”

Read: Spotted lanternfly ‘could reach Michigan at any time’: What to know about this invasive species

What to look for when checking for Asian longhorned beetles

Asian longhorned beetles have not yet been discovered in Michigan, but environmental officials want residents to keep an eye out.

If infestations are discovered early, it can prevent widespread damage to forests, urban landscapes and maple syrup production.

Look for the following signs when you’re outside:

  • 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.

Adult Asian longhorned beetles are large and range from 3/4 to 1 1/2 inches in length. That doesn’t include their long antennae. They are shiny black and have random white blotches, or spots.

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.

The Asian longhorned beetle is a large, shiny black beetle with irregular white spots and black and white banded antennae. (USDA APHIS PPQ)

Read: Let’s talk about Michigan’s 2 invasive mammals: A large, destructive rodent and aggressive wild boars

Native bugs that look similar

There are a few beetles and bugs that are native to Michigan but can be mistaken for the Asian longhorned beetle:

  • 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.

What to do if you find an Asian longhorned beetle

If you find an Asian longhorned beetle or a tree that appears to have been damaged by it, you should report it.

If you can, catch the beetle and keep it in a jar. Take note of the location and send the information with the USDA or contact MDARD at 800-292-3939 or MDA-info@Michigan.gov.


About the Author:

Kayla is a Web Producer for ClickOnDetroit. Before she joined the team in 2018 she worked at WILX in Lansing as a digital producer.