Western Pine Beetle - Field Guide to Diseases and Insect Pests of Idaho and Montana Forests

Western Pine Beetle

Dendroctonus brevicomis LeConte

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

Hosts. – Ponderosa pine.

Distribution. – May be found throughout host range.

Damage. – Larvae and adults feed in phloem layer of inner bark, eventually feeding into outer bark. Feeding girdles and kills the tree. Blue stain fungi are introduced. Usually larger diameter trees are killed, but may kill trees down to 6 inches d.b.h.

Identification. – Initial attacks on a standing tree, in early or later summer, are made about midbole and subsequent attacks fill in above and below. inconspicuous pitch tubes and red-brown boring dust indicate successful attacks. Egg galleries (fig. 37) wind both laterally and longitudinally, crossing and recrossing each other in a maze-like, serptentine pattern which forms a distinctive "signature" of the western pine beetle. Larvae can be found under or in the corky outer bark most of the year. Adults are dark brown to black and slightly less than one-fourth inch long. Trees attacked in September fade the following spring. Those attacked during the summer may fade even before the beetles emerge, depending on weather conditions in any given year. Woodpeckers may flake away bark in search of overwintering larvae.
Image Unavailable

Figure 37 - Western Pine Beetle egg galleries
showing characteristic "serpentine" pattern.

Similar damages. – May be confused with mountain pine beetle or secondary beetles. Conspicuous serpentine galleries distinguish western pine 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.

DeMars, C. J., Jr., and B. H. Roettgering. 1982. Western pine beetle. USDA For. Serv., Forest Ins. & Dis. Leaflet 1, 8 p., illus.

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

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