Canadian Forest Service Publications

Spatial relationships between western blackheaded budworm (acleris gloverana) (lepidoptera: tortricidae) defoliation patterns and habitat zones on Vancouver Island, British Columbia. 2001. Otvos, I.S.; Borecky, N.; Shepherd, R.F.; Dewey, A. Pages 133-143 in A.M. Liebhold, M.L. McManus, I.S. Otvos, and S.L.C. Fosbroke, editors. Proceedings - Integrated management and dynamics of forest defoliating insects, August 15-19, 1999, Victoria BC, Canada. USDA Forest Service, Northeastern Research Station, Newtown Square, PA, General Technical Report NE-277.

Year: 2001

Issued by: Pacific Forestry Centre

Catalog ID: 18314

Language: English

Series: USDA General Technical Report

Availability: Order paper copy (free)

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The western blackheaded budworm (Acleris gloverana (Walshingham)) is a cyclic defoliator of western hemlock (Tsuga heterophylla (Raf.) Sarg.). At least seven blackheaded budworm outbreaks have occurred in British Columbia and severe defoliation has been recorded during five of these outbreaks on Vancouver Island. Spatial patterns of past blackheaded budworm outbreaks on the Island were examined by overlaying them with biogeoclimatic units, elevation, and climate data to identify and rate stands susceptible to outbreaks. Three variants of the Coastal Western Hemlock biogeoclimatic zone, in decreasing order of susceptibility, were CWHvm1, CWHvm2, and CWHvh1. In addition, small areas of the Mountain Hemlock zone (MHmm1) were also defoliated. Only a small area on the northern tip of Vancouver Island was defoliated during three of the four outbreaks. Based on these results, we recommend locating permanent sentinel pheromone monitoring traps in the repeatedly defoliated area on northern Vancouver Island. We also recommend conducting additional larval sampling in the CWHvm1, CWHvm2, and CWHvh1 biogeoclimatic units to confirm rising pest populations based on pheromone trap catches so that control options may be examined prior to serious damage to the stands.