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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.
Back to Douglas-fir Trees
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