Oregon Forestry Pesticide Applicator Practice Exam

Bark beetles rely on flight to move between trees and use pheromone signals to organize attacks on hosts that are stressed or damaged. The Douglas-fir beetle is a classic example: it targets Douglas-fir, disperses in flight aided by prevailing winds, and is strongly drawn to hosts by aggregation pheromones that help many beetles converge on the same tree. When large blowdowns occur and salvage logging is not done, there’s an abundance of downed, stressed, or dying trees that provide ideal breeding material and entry points, allowing populations to swell and outbreaks to worsen. Although other beetles may also fly and respond to pheromones, the specific combination of attacking Douglas-fir, wind-driven dispersal, pheromone attraction, and the outbreak pattern following un salvaged blowdown points most clearly to the Douglas-fir beetle. Spruce spider mites are not bark beetles and don’t fit this scenario, and mountain pine beetle or pine engraver beetle involve different host trees and outbreak dynamics.