"Damaging Agents- The mountain pine beetle (Dendroctonus ponderosae) is the most severe insect pest of lodgepole pine. The epidemics that periodically occur in many lodgepole pine stands seriously affect the sustained yield and regulation of managed stands.

Adult beetles attack lodgepole pine in July or August, introducing bluestain fungi (8). The beetles construct egg galleries in the phloem where larvae feed and together with the fungi, girdle and kill the tree. Larvae overwinter in the tree, complete development, and emerge as adult beetles in the spring.

Harvesting has been considered as a means of preventing mountain pine beetle epidemics (19). Silvicultural practices in an integrated program for controlling losses to mountain pine beetle have been suggested (9,18). No mortality occurred in heavily thinned stands in Oregon where vigor ratings were high (44)."
http://forestry.about.com/library/silvics/blsilpincon.htm

"Mountain pine beetles play an important role in the dynamics of natural lodgepole pine stands. The beetle periodically invades stands, killing many individuals and creating large amounts of fuel. These fuels are eventually consumed by fire, creating a favorable seed bed for lodgepole regeneration. This cycle increases the probability that lodgepole pine will reoccupy a site at the expense of other species.

Adult beetles attack lodgepole pine in July or August by tunneling through the bark and laying eggs. Beetles introduce blue stain fungi, which in conjunction with larvae feeding on the bark, cause girdling which kills the tree. Larvae overwinter in the tree, complete their development, and emerge as adults in the spring to attack new trees. Epidemics can kill up to two thirds of a stand's large trees. Infestations commonly last 5 to 7 years, and reoccur in 20- to 40-year cycles."
http://www.cnr.berkeley.edu/departments/espm/extension/LODGEPOL.HTM