Bark beetles (Scolytidae) in Eastern Oregon and Washington
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Bark beetles are well described in terms of life history and general ecology for the six beetle species of concern in eastern Oregon and Washington, USA: Douglas fir beetle, Dendroctonus pseudotsugae; mountain pine beetle, D. ponderosae; western pine beetle, D. brevicomis; spruce beetle, D. rufipennis; fir engraver, Scolytus ventralis; and, pine engraver, Ips pini. Many interactions between bark beetles and other agents and resources have been described. Wildfire, windstorms, disease, other insects, and land management practices can weaken trees and attract bark beetles that become locally epidemic. At low population levels, beetles perform useful functions by creating habitat and forage for many organisms, but outbreaks can cause extensive tree mortality and increase risk of wildfire. Natural control agents such as birds, predatory beetles, parasitoids, and parasites, have been studied, but have not been employed operationally in management strategies. While semichemical-baited traps provide information about population fluctuations locally, large area monitoring relies primarily on aerial surveillance. Stand susceptibility, hazard, or risk-rating systems exist for most of these species, and infestation growth or damage models are available for a few. In most cases, pesticide sprays, attractants and anti-aggregants, and trap-tree techniques have been useful in specific applications. Anti-aggregants have been proven useful in large-scale operations for Douglas fir beetle. Salvage or sanitation of infested, wind- or fire-damaged trees can prevent population build-ups if done promptly. Integration of these methods along with prescribed fire and tree thinning has been recommended. Decision-support tools are becoming more prevalent but each requires validation for different geographic variants.