Canadian Forest Service Publications

Douglas-fir tussock moth damage in British Columbia. 1987. Alfaro, R.I.; Taylor, S.P.; Wegwitz, E.; Brown, R.G. The Forestry Chronicle 63(5): 351-355.

Year: 1987

Issued by: Pacific Forestry Centre

Catalog ID: 2655

Language: English

Availability: PDF (request by e-mail)

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The Douglas-fir tussock moth (Orgyia pseudotsugata McDunnough) defoliated Douglas-fir (Pseudotsuga menziesii var glauca [Beissn.] Franco), in British Columbia from 1981 to 1983. Forty-five defoliated and 16 non-defoliated (check) plots were monitored for defoliation and damage from 1982 to 1985. By 1985, cumulative mortality and top-kill in the defoliated plots averaged 51% (49% by volume) and 11%, respectively. Check plots sustained no mortality and less than 1% top-kill due to causes other than tussock moth defoliation. Mortality occurred very early in the outbreak, with 56% of the dead trees already dead by 1982, generally after 1 year, but at most after 2 years of defoliation. Mortality and top-kill were related to the number of seasons of defoliation and, particularly, to defoliation intensity. It was concluded that Douglas-fir tussock moth is an important depletion factor of Douglas-fir in British Columbia.