Western Spruce Budworm Damage to Sprayed and Unsprayed Young Douglas-Fir

Authors: Alfaro, Rene I.¹; Wegwitz, Emil¹

Source: Western Journal of Applied Forestry, Volume 3, Number 2, 1 April 1988 , pp. 44-46(3)

Publisher: Society of American Foresters

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Abstract:

Defoliation, mortality, and top-kill were measured in 40-year-old, open-grown Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) under attack by the western spruce budworm (Choristoneura occidentalis [Freeman]) in the interior of British Columbia, in control trees and trees treated with ground sprays of the insecticide Sevin. In untreated trees that sustained repeated defoliation of 50 to 90% of the total crown foliage, tree mortality began after four years and had reached 29% after eight years. Thirty-four percent of the survivors in this group suffered top-kill, which averaged 1.0 m at the end of eight years. No mortality and only negligible top-kill occurred in trees, sprayed or not, which sustained less than 50% defoliation. A regression model of the probability of tree mortality based on the defoliation is presented. West. J. Appl. For. 3(2):44-46, April 1988.

Document Type: Journal article

Affiliations: 1: Canadian Forestry Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, B.C., Canada V8Z 1M5

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