Oregon Forestry Pesticide Applicator Practice Exam

When a large windthrow occurs, a huge amount of downed Douglas-fir becomes freshly dead, freshly cambium exposed, and highly attractive to bark beetles. The Douglas-fir beetle specializes in attacking and reproducing in such recently killed or damaged Douglas-fir. If salvage logging isn’t done, that downed material stays in place, providing a ready-made breeding and feeding substrate and allowing beetle populations to build and spread to nearby live trees. Over time, this can trigger and sustain outbreaks.

Other pests aren’t as directly tied to windthrow in the same way. Western spruce budworm mainly defoliates live spruce and fir and follows its own population cycles, not the downed timber created by windthrow. Pine engraver beetles target pines, and mountain pine beetles are driven more by drought and temperature conditions rather than windthrow blowdowns.