Illustrated Guide to Pests


Mountain pine beetle, Dendroctonus ponderosae

The mountain pine beetle is the most devastating insect in British Columbia’s forests, killing vast tracks of lodgepole pine. Outbreaks occur about every 10-15 years in the Kamloops Region and can reach thousands of hectares in size.

Host trees: Its primary host is lodgepole pine, however in B.C. the MPB attacks ponderosa, western white and whitebark pines.

Description and life cycle: Adult mountain pine beetles are hard, stout-bodied, cylindrical, brown-black insects ranging in length from 3.5 to 6.5 mm. In general, the mountain pine beetle has a one year life cycle. Adults fly and attack susceptible trees in late July through August. Trees produce large amounts of resin toxic to the beetle when attack occurs. In order for insects to successfully overcome the defence mechanisms of a tree, large numbers of beetles must aggregate and attack within a very short time frame (mass attack). Attacking beetles introduce a blue stain fungus that combined with gallery construction kill the tree. Females initiate attack by burrowing under the bark and emitting a pheromone that attracts males. Once the tree is full of beetles, anti-aggregation pheromones are released thereby ceasing further attack.

After mating, females tunnel upwards and lay eggs on alternate sides of the gallery. When the eggs hatch the larvae mine out horizontally from the main gallery. Eggs hatch in 2 weeks and 1st instar larvae mine perpendicular to the parent gallery. The mountain pine beetle develops through 4 instars, overwintering as 3rd instar larvae.

Development is completed the following spring. Mature larvae excavate a chamber and pupation occurs in early to mid-summer. Pupae moult to immature (callow) adults. Beetles then feed on the blue stain fungi within the pupal chamber for up to 2 weeks prior to emerging. Finally, from mid to late July, mature beetles bore out of the bark and attack new hosts, thereby completing the cycle.

Attacked trees can be recognized by pitch tubes on the bole, frass and sawdust around the base, and red foliage the season following attack.

Last updated on January 28, 2008
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