Michigan DNR asks people to look out for invasive Asian longhorned beetle

The Asian longhorned beetle. Photo courtesy of the Animal and Plant Health Inspection Service. 

It's August, which means that it is officially "Tree Check Month."

The Michigan departments overseeing natural resources, agriculture, and the environment are asking residents to dedicate 10 minutes of their day towards checking the trees around their homes for the Asian longhorned beetle.

The Asian longhorned beetle is a non-native wood-boring beetle. These beetles have a shiny black color with random white spots. This species is considered invasive because it attacks 12 types of hardwood trees including, maples, elms, horse chestnuts, birches, and willows.

That's a problem for states with any of those native tree species since the invasive beetle has no natural predators. Trees infested with the Asian longhorned beetle eventually die after being invaded.

Although this invasive species has not yet been found in Michigan, it is important to keep an eye out for it. Identifying early signs of infestation can prevent widespread damages to Michigan's forest resources, urban landscapes, and maple syrup production. 

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The US Department of Agriculture says that there are 15 known infestation sites in the U.S. Five of these infestations were detected and reported by alert citizens.

Checking for tree damage:

  • Round exit holes - about the diameter of a pencil - found in tree trunks and branches
  • Shallow ovals or round scars in the bark where the adult beetles chewed the 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

Searching for Asian longhorned beetles

  • Adult Asian long horned beetles are very large, ranging from ¾ to 1 ½ inches in length. (not including their antennae)
  • The beetles are shiny black with random white spots or blotches.
  • Their antennae have alternating black and white segments.
  • They have 6 legs that can either be black or partly blue.

Be aware of lookalikes

  • The white-spotted pine sawyer has a distinctive white spot below the base of its head – between its wings – and is brownish.
  • 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.

Anyone that observes an Asian long horned beetle, or a tree that appears to be damaged by one, is asked to report it. If possible, capture the beetle in a jar, take photos, record the location and report it to AsianLonghornedBeetle.com or contact MDARD at 800-292-3939 or MDA-info@Michigan.gov.