Tree mortality caused by the western hemlock looper in landscapes of central British Columbia

Abstract

An outbreak of the western hemlock looper, Lambdina fiscellaria lugubrosa (Hulst) (Coleoptera: Geometridae), caused tree mortality in central British Columbia, Canada, to stands composed of alpine fir, Abies lasiocarpa (Hook.) Nutt., western hemlock, Tsuga heterophylla (Raf.) Sarg., white spruce, Picea glauca (Moench) Voss, and western red cedar, Thuja plicata Donn. After 4 years, high levels of tree mortality (51–96% of all trees with DBH ≥ 7.5 cm) occurred in areas of severe defoliation classifying this pest as a serious depletion agent of British Columbia forests. Tree mortality occurred rapidly, mostly within 2 years of the start of the infestation. Equations are provided to allow foresters to determine expected mortality levels with reasonable precision. A higher proportion of mortality occurs on alpine fir rather than on other species.