Keep Calm and Watch for the Asian Longhorned Beetle

Since the Emerald Ash Borer first invaded Michigan in 2002, it has killed millions of native ash trees across the state, and even more across the country. But despite its continued importance in Michigan, the Emerald Ash Borer is not the only invasive insect responsible forest landowners should be looking out for.

While the Asian Longhorned Beetle (ALB) has not yet been found in Michigan, it has been found in states as close-by as Ohio and Illinois. The Michigan Department of Agriculture and Rural Development (MDARD) and Michigan State University have been actively monitoring for ALB at various sites throughout the state for several years, and plan to continue to do so in the future.

Unlike the Emerald Ash Borer, the ALB feeds on multiple genera of trees. Maples are its most-preferred hosts, and ALB is feared to have the potential to decimate the timber and maple syrup industries. ALB also prefers willows, buckeyes, elms and birches. While it’s a less-preferred host, ALB can even attack the already-decimated ashes of Michigan.

Like Emerald Ash Borer, ALB is also feared to be devastating to landscape and street trees, as its favored host is the non-native (and, in many contexts, invasive in its own right) Norway Maple (Acer platanoides).

Asian Longhorned Beetle. Photo by Michael Bohne, USDA Forest Service, Bugwood.org

Eradication efforts to control the ALB can themselves be devastating and aesthetically unappealing. The current practice when an infestation is discovered is to use a combination of insecticides and the removal of all potential host trees within a half-mile radius of the infected tree. Early detection of an infestation is therefore very important, especially if you want to protect your street trees!

So, what should you look out for? ALB attacks the top of a tree first, which can cause dieback of the crown. Dieback can be caused by many factors, but if you have a maple tree that is experiencing dieback, you may want to have it looked at. Looking for the exit holes left by adult beetles can also be a clue: these holes are about a half-inch wide, and can extend an inch into the tree. You can also look for what appears to be sawdust on the ground, caused by a combination of the beetle chewing through wood and their excrement.

There are native look-alikes in the same family as ALB that are native to Michigan, so if you find a beetle you think may be an ALB, it’s better to be safe than sorry! Take it in to the Shiawassee Conservation District at 1900 S. Morrice Road in Owosso, and we can pass it on to the people who can make a definitive identification.

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