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Budworm H. P. Koot
The western blackheaded budworm, Acleris gloverana (Walsingham) (Lepidoptera: Tortricidae), is a defoliating insect occurring throughout British Columbia that periodically causes extensive defoliation of coniferous forests. Severe damage occurred on the coast in the 1940s and 1950s, notably on northern Vancouver Island and the Queen Charlotte Islands; there was some tree mortality. In the interior, there were smaller infestations at several localities in the 1950s but little tree mortality was recorded. From 1965 to 1968, there was light to moderate defoliation over much of the hemlock forests of the Kamloops and Nelson forest regions, and along the Hope-Princeton Highway east of Hope. In 1969, scattered heavy defoliation occurred in hemlock stands from Howe Sound to Harrison Lake north of the Fraser River. Many hemlock forests were severely defoliated on Vancouver Island from Jordan River to Holberg in 1970. Although defoliation occurred on over 166 000 ha in 1972, the infestation subsided in 1973 without significant tree mortality. The Queen Charlotte Islands and the adjacent mainland coast were lightly defoliated by the western blackheaded budworm in 1972; by 1974 defoliation extended over 127 000 ha, but tree mortality was restricted to several small patches of forest. Populations continued at mainly endemic levels until 1984 when 19 000 ha of old-growth forest were defoliated in Revelstoke and Glacier national parks. After extensive feeding in 1985, defoliation peaked at 56 000 ha on the Queen Charlotte Islands and near Kitimat in 1986. By 1987, successive years of defoliation by budworms in conjunction with hemlock sawfly, Neodiprion tsugae Middleton, resulted in 25% mortality of second-growth hemlock over 3100 ha on the Queen Charlotte Islands. Since then, small infestations have occurred on northern Vancouver Island, most notably over 7400 ha near Holberg in 1988. Some top-kill and mostly light defoliation of subalpine fir occurred in the eastern part of the Prince Rupert Forest Region from 1982 to 1988. By 1990, populations subsided to mostly non-damaging levels across the province.
For more information, see the Western Blackheaded Forest Pest Leaflet in the Canadian Forest Service bookstore.