It’s sweeping the country, and their music is not sweet to the ear. Instead of being melodic, it goes “chomp chomp” and is repeated millions of times in tunnels under the bark of Western Montana’s Ponderosa Pine.
The beetles emerge from infested host trees, usually dead or dying, in summer and attack living trees. They bore into the bark, tunnel under it, and lay eggs. Eggs hatch into larvae, which kill the tree by excavating a network of tunnels out from the egg chamber and girdling the tree. Larvae over-winter and emerge as adult beetles the following summer to repeat the cycle.
The small forest owner can limit the spread of the beetle by felling infested trees before the larvae can complete the life cycle. If the infestation is caught early, before it affects too many trees, control is feasible.
A completely brown-needled, dead ponderosa is the result of pine beetle infestation. By the time the needles are brown, adults have emerged to attack other trees and removing the dead tree will not limit the infestation.
The pitch tube results when the tree attempts to repel the beetle boring into its bark. The felled tree illustrated had hundreds of pitch tubes up to a height of about 50 feet. The tree was healthy, measured about 14 inches in diameter, and was more than 120 years old.
Pitch tube closeup.
The small landowner with just a few infested trees can control the beetle by felling the tree, cutting it into manageable sections, and peeling away the bark. A cradle made from 2 X 4’s holds the log; a drawknife is used to peel off the bark.
Exposed egg chamber, with two adult beetles. Interrupted at this stage of its life cycle, the beetle will not re-infest another tree.
The beetle is about ¼ inch long.
Peeled logs, stacked to dry over the summer, will be excellent, seasoned firewood for the next winter.
Branches from the infested tree usually don’t contain pine beetles, but need to be protected from becoming infested with another pest, the ips beetle. This beetle does not normally attack living trees but will do so in cases where the population builds to great numbers. To prevent infestation, the branches are covered with plastic until they are dried and can be burned.