Western Balsam Bark Beetle

Dryocoetes confusus Swaine

From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54

Hosts. – Subalpine fir and occasionally grand fir.

Distribution. – Throughout host range.

Damage. – Adults and larvae feed in phloem layer of inner bark. Blue stain fungi are introduced. Trees may be strip attacked or attacked in suf- ficient numbers to kill them.

Identification. – Trees often are attacked in groups (fig. 55). External evidence of attack on the boles of standing trees is hard to detect. Entrance holes and boring dust on the bark may be visible in August. Pitch flow may be evident. Males bore into the phloem, excavate a nuptial chamber, and mate with several females. Egg galleries radiate from the central nuptial chamber in a random pattern. Larvae extend their mines from the main egg galleries until freezing weather, then become dormant. Attacked trees generally turn yellow-red within a year. Adults are shiny, dark brown, cylindrical beetles about one-eighth inch long (fig. 52). Their thorax is evenly convex above and their posterior is abruptly rounded and without spines.
	Figure 55 - Subalpine fir mortality caused by Western Balsam Beetle.
Image Unavailable	Image Unavailable
Figure 56 - Egg and larval gallery pattern of Western Balsam Bark Beetle.	Figure 52 - Comparison of body shapes of four common genera of bark beetles.

Similar damages. – Other bark beetles may kill subalpine fir, but gallery pattern and characteristics of adult beetles distinguishes this beetle from associates. Root diseases are often associated with attacks by western balsam bark beetles.

Link to Images in Forestry Images

References.

Anonymous. 1982. For. Insect & disease identification and management. USDA For. Serv., Northern Region; Idaho Dept. of Lands, Insect and Disease Control; Montana Dept. of State Lands, Division of Forestry. 192 p.

Furniss, R.L., and V.M. Carolin. 1977. Western For. Insects. USDA Forest Serv., Misc. pub. 1339, 654 p., illus.

[  Back  ]