Wood-boring insect communities in young, top-killed western larch (Larix occidentalis)

Western larch (Larix occidentalis) is an iconic native tree species in mixed-conifer forests of the Pacific Northwest. This deciduous conifer is frequently used in restoration plantings because of its resistance to most pathogens and wood-boring insects. It is suspected that top-killed trees are the result of attack by the moth Cydia laricana (Lepidoptera: Tortricidae). Sites were selected with stands of damaged larch, and we also created two different types of artificially stressed trees. The three treatments examined were naturally attacked trees, girdled trees, and fake snags. Site parameters, including soil chemistry and stand composition, were also examined. Trees were brought into the lab following insect attack. Portions of the tree had the bark removed to excise embedded insects, and the remainder of the tree was placed in rearing cages. Insects emerging the following year were collected and identified. Families of insects causing economic damage to these trees included Tortricidae, Cerambycidae, Buprestidae, Curculionidae, and Braconidae. Analysis of these communities has received little attention in the past. We compared insect community indices (abundance, richness, evenness, and diversity) across the three categories of stressed trees. Results will be used to understand how site characteristics, stand composition, and insect communities impact restoration efforts of western larch.