There are several species of Ips bark beetles, also called engraver beetles, which primarily attack pine and spruce trees. These beetles are about the size of a dull pencil point, and adults vary in color from brown to black.
Trees may not show symptoms such as dull or faded foilage, drooping needles or needle drop until it's too late. All stressed trees are vulnerable to attack and should be examined for signs of beetle activity. Sawdust being expelled from various points on the tree's trunk is a sure indication that the beetles are active.
These beetles are normally not a problem in healthy trees, however, if trees are weakened by drought, construction damage, lightning or soil disturbances, the beetle can attack.
The key to control is prevention. Water, fertilize and mulch trees to keep them at maximum vigor. If possible, remove weakened or infested trees to keep bark beetles and other borer populations minimized.
If beetles are still a threat, two or three applications of an appropriate insecticide may be needed to prevent beetle attacks. Season-long protection is required until the trees have weathered the stressful conditions and are once again vigorous.