In stands with ongoing infestations of tree-killing bark beetles (Coleoptera: Curculionidae: Scolytinae) such as mountain pine beetle (Dendroctonus ponderosae Hopkins) and Douglas-fir beetle (D. pseudotsugae Hopkins), anti-aggregation pheromones can act to divert potentially attacking beetles away from a tree that has already been fully colonized. By diverting additional beetles from attacking a fully colonized tree, competition among developing larvae for the within-tree nutrients should decrease. We placed traps baited with two known bark beetle anti-aggregation pheromones, verbenone and 3-methylcyclohex-2-en-1-one (MCH), in mixed conifer stands to determine if the compounds were attractive to individual species in five beetle families (Curculionidae, Buprestidae, Cerambycidae, Trogositidae and Cleridae) known to be associated with tree-killing bark beetles. Four species were caught in significantly higher numbers in traps baited with verbenone compared with non-baited traps or traps that were baited with MCH. No species were captured in significantly higher numbers in the MCH-baited traps. The species that were attracted to the verbenone-baited traps included a bark beetle (Pityogenes fossifrons (LeConte)), a buprestid (Buprestis lyrata Casey), one cerambycid (Megasemum asperum (LeConte)) and a trogositid (Temnochila chlorodia (Mannerheim)). Aside from being a beetle-produced anti-aggregation pheromone, verbenone is also produced by some conifers as the trees die. It is possible that insect species that depend on stressed or dying trees as host material may utilize verbenone as a cue for host location.
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