Spruce Beetle

Dendroctonus rufipennis (Kirby)

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

Hosts. – Engelmann spruce, rarely lodgepole pine.

Distribution. – Wherever Engelmann spruce is found in Idaho and Montana.

Damage. – Larvae and adults feed in phloem layer of inner bark. Completely girdled trees are killed; however, strip attacks (successful attacks that do not kill the tree) may be made. Tree is inoculated with blue stain fungi. Trees less than 12 inches d.b.h. are infrequently attacked.

Identification. – Look for red-brown boring dust on bark, in bark crevices, and on ground around base of host from mid-May to July (fig. 33). During the winter, woodpeckers will flake off pieces of bark which accumulate on the ground or snow around infested trees. Egg galleries average about 5 inches in length, have a slight crook at the start, and extend upward in standing trees. Eggs are deposited on alternate sides of the gallery which is packed with frass (fig. 34). Larvae feed in the phloem, usually gregariously, often forming fan-shaped galleries. Larvae are present for two summers, pupate, then overwinter the second year as adults in the bark. Infested trees usually do not turn yellow-green until I year after attack. Adult beetles are dark brown to black with red wing covers and are about one-fourth inch long.

Similar damages. – Secondary bark beetles may produce boring dust. Gallery patterns distinguish them from the spruce beetle.

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. 

Schmid, J. M., and R. C. Beckwith. 1975. The spruce beetle. USDA For. Serv., For. Pest Leaflet 127, 7 p., illus. 

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