|
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.
|
