Douglas-Fir Beetle in the Intermountain West
The most important bark beetle pest of Douglas-fir is the Douglas-fir beetle. Dendroctonus pseudotsugae Hopkins. Beetles in fest and kill their host throughout most of its range in western North America. Western larch may be attacked during beetle outbreaks, but brood development in larch is rare. At low population levels, beetles maintain themselves in windthrown or injured trees, or those infected with root diseases. In endemic conditions, tree mortality may be widely scattered throughout a stand or watershed. Epidemics-almost always associated with some type of stand disturbance such as blowdown, defoliation, fire, or drought-can build rapidly and kill hundreds to thousands of mature Douglas-fir in stands or drainages. Beetles are attracted to downed or weakened trees and are capable of multiplying quickly due to lack of host resistance. Beetle populations at higher than normal levels then overcome live, relatively healthy trees nearby.
Douglas-fir beetle in the Intermountain West (1999). USDA Forest Service, Northern and Intermountain Region, Brochure R1-99-102. 6 pp.