Western balsam bark beetle, Dryocoetes confusus,

Fig. 74   Adult.	Fig. 75  Larva.	Fig. 76   Attacked trees. Note: this colour usually appears within a year following an attack.	Fig. 77  Egg and larval galleries.

Tree Species Attacked: Primarily sub-alpine fir is attacked, but occasionally, amabilis fir. Some attacks of white spruce and Engelmann spruce have been recorded. Mature trees are targeted.

Insect Description & Damage Symptoms: Adults are 3.4 to 4.3 mm long, dark brown, and covered with erect, red-brown hairs. They emerge in late May or June. The life cycle normally requires two years, but given the right climatic conditions, it could be completed in one year.

The extent of an infestation is difficult to determine as a result of overlapping life cycles, a lack of telltale pitch tubes, and the fact that the majority of the attacks occur above 2 m on the bole. The adults construct egg galleries that have a central nuptial chamber with brood galleries radiating from the top and bottom. A mixture of boring dust and frass is usually found in bark fissures and at the base of the bole. The foliage of an attacked tree will change from green to a bright, brick-red colour in the year following the attack, but the red needles may be retained for up to five years.

Damage: Given the appropriate conditions, balsam bark beetles can be responsible for extensive tree mortality in stands containing a large percentage of the preferred host. Normally, however, less than 5% of a stand is attacked in a single season, with the damage usually scattered throughout the stand. The adult carries a lesion-causing fungus, Ceratocystis dryocoetidis, which is responsible for an estimated 65% of the mortality associated with balsam bark beetles. The lesions caused by the fungus may girdle and kill a tree, and they also make the tree susceptible to further beetle attacks.

Back to the Pest Field Guide Index

Contact Tim Ebata if you have comments on the presentation of this information.

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