Signs of emerald ash borer infestation in ash trees include the thinning and death of upper branches in the canopy and sometimes new sprouts emerging from the trunk after upper parts of the trees die. The bark may split open, and woodpecker activity may remove patches of bark. When larvae turn into adult beetles and emerge, they create tiny D-shaped exit holes in the trees.
To confirm outward signs of emerald ash borer infestation, observers can peel back the bark to expose tube-like galleries that are usually full of excrement and sawdust. They may also see segmented cream-colored larvae up to 1 1/4 inches long. The half-inch adult beetles are bright metallic green on the surface and metallic purple-red under their wings.
Female emerald ash borers lay their eggs on the bark of ash trees, and when the larvae hatch, they bore into the trees and feed on the tissues that transport nutrients within the trees. Although they prefer trees that are stressed and dying, the beetles also attack healthy trees. Heavily infested trees can die within two to five years. Females can fly up to half a mile from where they emerge before laying their eggs, but infestation often spreads due to transportation of infested firewood from one area to another. Some central and eastern states quarantine infested areas, and transporting firewood out of quarantined areas is illegal.