Western Pine Beetle

Abstract

The western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae, Scolytinae), is a bark beetle native to parts of western North America. The beetle colonizes and kills ponderosa (Pinus ponderosa) and Coulter (P. coulteri) pines. Western pine beetle prefers to colonize larger diameter trees (>20 inches [50 centimeters (cm)] diameter at breast height [DBH]) but will attack and kill trees of most ages and sizes during outbreaks. Rarely is slash or other logging debris colonized. The beetle may cause mortality of 60 to 90 percent of host trees in some landscapes (fig. 1). The most recent notable outbreak occurred in the central and southern Sierra Nevada Range in California from 2014 to 2017, causing mortality of millions of ponderosa pines. This outbreak, as with many other outbreaks of western pine beetle, was incited by drought and supported by landscapes of high-density host trees. The frequency and severity of droughts are expected to increase likely influencing the frequency and severity of future western pine beetle outbreaks.

Citation

Homicz, Crystal S.; Fettig, Christopher J.; Munson, Steven A.; Cluck, Daniel R. 2022. Western Pine Beetle. Forest Insect and Disease Leaflet No 1. FS-1192. Portland, OR: USDA-Forest Service, Pacific Northwest Region. 15 p.