Western larch may be attacked but seldom, if ever, is brood produced in those trees. Douglas-fir is found in Idaho and Montana. Strip attacks may be made.
Tree is inoculated with blue stain fungi.
Trees less than 12 inches d.b.h. are seldom attacked. Attacks are often high on the tree's bole, so careful inspection may be required to determine if beetles are present. In the phloem, egg galleries are parallel to wood grain and are commonly 8 to 10 inches in length. Larvae mine outward from the egg gallery and later eed toward the outer bark. Most broods overwinter as adults in the outer bark.