Emerald ash borer is a new insect from China. Arborists, landscapers, and other horticulturists should be watchful for this pest and its damage. Recent newspaper accounts have increased the public’s interest in the emerald ash borer.

Emerald ash borer was detected in southeast Michigan in 2002. It has also been detected in Windsor, Ontario, and was discovered in Toledo during the winter. It is originally from Asia. In the United States, it is known to attack only white, black, and green ashes.

Adults are slender, dark metallic green, 1/2-inch beetles that are present from mid-May to late July. The creamy white larvae are found under the bark.

Infestation results in severe dieback of the upper third of the canopy, with the tree being killed in 2 years. The adult beetles make a D-shaped exit hole when they emerge. Tissue produced by the tree in response to larval feeding may cause vertical splits to occur in the bark. Distinct S-shaped tunnels may also be apparent under the bark.

Because this pest is highly destructive, the Michigan Department of Agriculture placed a quarantine on all ash trees and ash wood products, including firewood, in the affected counties to prevent and control its spread. If this beetle is detected, contact the Illinois Department of Agriculture or your local University of Illinois Extension Office.