There are numerous beetles that attack bark on trees and thus are categorized as bark beetles. Most are there because the bark is dead but others can be very destructive to weakened or stressed trees. The stresses can be due to a wide range of conditions such as weather related, mechanical injury, chemical injury, aging, growing site and planting. The over-wintering stage can be larvae, pupae or adults. Adults lay eggs in galleries that are mostly in the phloem but a few lay eggs in the xylem. The first beetles attacking a tree often give off a strong scent that attracts other beetles to invade the tree. The eggs hatch, larvae feed then pupate. Adults eventually emerge to start the cycle all over. Depending on the bark beetle and area of the country, there is from one to six generations per growing season.
Control is to minimize stress factors on the tree. Keep trees healthy, remove infested branches or trees (bark beetles will attack healthy pines next to dying pines so remove dying trees promptly) and destroy infected material by chipping burying or burning (where legal).