Feedback on new bark and ambrosia beetles in Michigan

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Updated from an original article written by Dave Smitley, Michigan State University Extension, Department of Entomology.

Two cases of black stem borer and ambrosia beetle were found in Michigan.

I received two quick responses to the article on new bark and ambrosia beetles recently found in Michigan written in May. In the first case, a nursery in southern Michigan reported extensive damage to young apple trees 2 to 2.5 feet in diameter. Beetles collected from the dead and dying trees were sent to MSU where Dr. Anthony Cognato identified them as Xylosandrus germanus, the black stem borer (Photo 1). Frass tubes the diameter of pencil-lead were also found protruding from infested apple trees (Photo 2).

Black stem borer
Photo 1. The black stem borer. Photo credit: Steve Valley, Oregon Department of Agriculture.

Frass cloumn of black stem borer
Photo 2. Frass column of black stem borer protruding from entrance tunnel. Photo credit: G. Keith Douce, University of George, Bugwood.org

In the second report, photos were sent by Guerin Wilkinson, owner of GreenStreet Tree Care (Photo 3). Wilkinson found frass tubes protruding from some large Norway maples in Ann Arbor that were definitely made by an ambrosia beetle. These trees are declining for unknown reasons. At this time, we have not identified which ambrosia beetle it is or if the decline of these trees is due to the ambrosia beetles or other factors.

Frass tubes protruding from Norway maple
Photo 3. Tiny (diameter of a pencil lead) frass tubes protruding from a Norway maple in Ann Arbor. Photo credit: Guerin Wilkinson, GreenStreet Tree Care.

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