CSU Extension Mountain pine beetle has a one-year life cycle in Colorado. In late summer, adults leave the dead, yellow to red needled trees in which they developed.
Females seek out living, green trees that they attack by tunnelling under the bark.
Coordinated mass attacks by many beetles are common. MPB larvae spend the winter under the bark. They continue to feed in the spring and transform into pupae in June and July. Emergence of new adults can begin in early July and continue through September. Spores of these fungi contaminate the bodies of adult beetles and are introduced into the tree during attack.