Forest Pests: Insects, Diseases & Other Damage Agents

Importance. - One or more species of ash bark beetles are found in any given region of the United States. They attack and breed in weakened, felled, and storm-damaged trees; only occasionally do they attack healthy trees. On some sites of the dry Great Plains, the western ash bark beetle causes severe branch- and top-kill.

Identifying the Insects. - Adult beetles are slightly elongate, cylindrical, and 2.0 to 3.4 mm long. Dense areas of light- and dark- colored scales produce mixed bands or spots. Larvae are legless grubs with a white, slightly curved body and a light-brown head.

Identifying the Injury. - Injury to trees results from tunneling in the inner bark and surface of the sapwood. The large egg gallery has two branches extending across the wood grain in opposite directions from the bark entrance. Larval galleries radiate outward from the egg gallery. The bark may be peppered with 1-mm, round exit holes.

Biology. - Overwintering adults fly to susceptible trees in the spring where they burrow into the bark and begin laying eggs. Larvae pupate in small cells at the end of their tunnels. New adults burrow out to the bark surface. There are one to two generations per year. Adults overwinter in short feeding tunnels in the bark of living or recently felled trees.

Control. - Direct controls are rarely needed. Cultural controls include debarking felled trees and logs and/or burning them to prevent brood emergence. To prevent attacks insecticides may be applied to the bark.