I N S E C T S
Douglas-fir Tussock Moth
The Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), is an important defoliator of spruce, Douglas-fir, true fir and other conifers in the Rocky Mountain region. Feeding by the larvae can cause complete defoliation of heavily infested trees. Damage usually appears first in the tops of trees and progresses downward, sometimes over several years.
Western Spruce Budworm
The western spruce budworm, Choristoneura occidentalis Freeman, is the most widely distributed and destructive forest defoliator in western North America. Several outbreaks have occurred in Colorado, the largest exceeding two million acres. They commonly infest Douglas-fir and white fir. Occasionally, they also attack Engelmann spruce, blue spruce and sub-alpine fir.