Western Pine Beetle, Dendroctonus brevicomis,

Fig. 78    Larvae.	Fig. 79  Egg and larval galleries are usually packed with dust.	Fig. 80  Killed ponderosa pine.

Tree Species Attacked: Mature to old ponderosa pine trees are attacked.

Insect Description & Damage Symptoms: One to two generations of beetles are produced every year, depending upon the elevation. Adults are brown to black, cylindrical, stout-bodied, hard-shelled, and about 3 to 5 mm long. They construct long, meandering, dust-packed galleries in the cambium of attacked trees. During periods of heavy attack, the galleries may cross and re-cross, forming a complex network. The timing of western pine beetle attacks depends upon elevation, but in British Columbia they can occur any time from May to September.

Reddish-brown boring dust will be present on the base of attacked trees. Inconspicuous reddish-brown pitch tubes can sometimes be found in bark crevices. Needles will pale and then fade to yellow, to reddish-brown, and finally to red in the months following the attack. Flaking of the bark by woodpeckers in search of beetles or larvae is also a symptom of infestation.

Damage: Usually, the western pine beetle breeds in scattered, old, slow-growing, or diseased trees; and trees weakened by stand stagnation, lightning, fire, or mechanical injury. This beetle, however, will also attack and kill healthy young trees during an epidemic, although trees under 15 cm in diameter are seldom attacked. Attacking adults also carry the spores of a blue stain fungus that can invade and block, along with feeding larvae, the conductive vessels of the inner bark and sapwood.

Similar Damage: May be confused with the mountain pine beetle or secondary beetles. The conspicuous serpentine galleries distinguish the western pine beetle.

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BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated February 19, 2002