The Emerald Ash Borer (EAB) is a very destructive wood-boring insect pest of ash trees. Ash is the only known host of this borer in the United States. The exotic beetle is native to Asia, including China, Japan, Mongolia, Korea, the Russian Far East, and Taiwan. It was first discovered in North America in southeast Michigan in June 2002, although it was likely introduced at least 10 years earlier.
The Emerald Ash Borer is a small, metallic green beetle about 3/8" to 1/2" long and 1/16" wide that emerges from the inner bark of ash trees from May through September, creating a D-shaped exit hole. Minnesota Department of Agriculture considers May 1 to September 30 to be the flight season for Emerald Ash Borers (EAB). This means that EAB adult beetles are emerging from infested wood or trees and flying in search of new hosts during this time. EAB larvae complete their development by pupating into adult beetles in the spring and early summer.
The larva of the beetle is the destructive stage of the life cycle, disrupting the movement of nutrients and water uptake in the tree. A full-grown larva averages 1-1/2" in length and has a series of bell-shaped body segments.
This beetle attacks only true ash (Fraxinus sp.) including green ash (F. pennsylvanica), white ash (F. Americana), black ash (F. nigra) and blue ash (F. quadrangulata). Mountain ash (Sorbus sp.) is not a true ash and not susceptible to the borer.