Origin:
Most species in North America are native insects, with several species introduced from Europe.
Biology:
This genus of tiny bark beetles includes about 17 species in North America, of which 5 species are introduced invaders from Europe. They attack many species of trees and woody shrubs, and with heavy infestations possible they are capable of killing the plants, including one species that is a serious pest of chestnut trees. The life cycle is similar to the ambrosia beetles in which the female creates a gallery in the wood under the bark and deposits her eggs there. She also introduces a fungus that she cultivates and which the larvae then feed on. Development from egg to adult beetle takes 2.5 to 3 months and there typically are 2 generations per year. When the adult beetles emerge from the infested tree they leave behind a great many tiny, round exit holes, each about the diameter of a pencil lead.
Identification:
The tiny adult beetles are only about 2-3 mm long and are very compact and cylindrical, being more than twice as long as they are wide. Their color ranges from light brown to black and the wing covers have many short hairs over them, particularly along the sides. The head is tucked well under the prothorax and projects downward, being invisible when viewed from above. The antennae are typical of bark beetles with several very small and short segments and a much larger, rounded terminal club.
Characteristicts Important to Control:
Maintaining trees in a healthy state will help them to repel attacking beetles. Preventive applications of residual insecticides may be applied to the trunk and branches prior to the emergence of the adult beetles in the spring. Systemic insecticides may also be helpful, either as soil applied chemicals that are taken up by the roots or as trunk injections.
