Behavioral responses of eastern larch beetle (Coleoptera: Curculionidae: Scolytinae) to pheromone components and selected host-produced compounds in the Great Lakes region

The eastern larch beetle, Dendroctonus simplex LeConte, is a North American species of bark beetle that shares the distribution of its host, Larix laricina (Du Roi) K. Koch. A recent outbreak in the Great Lakes region has prompted renewed interest in the chemical ecology of eastern larch beetle and its natural enemies. Here, we describe field assays elucidating these insects' flight responses to host resin odors and pheromone components in Minnesota and laboratory olfactometer assays illustrating walking responses by eastern larch beetle to pheromone components produced by female beetles. In field trials, the addition of host monoterpenes ∆-3-carene and α-pinene to seudenol lures increased trap captures of eastern larch beetles. Similarly, α-pinene increased captures of Thanasimus spp. predators in seudenol-baited funnel traps. Frontalin release rates between 0.014-3.3 mg/day did not significantly alter catches of eastern larch beetles with seudenol alone, however, still higher concentrations of frontalin (24 mg/day) decreased catches. In contrast, increasing frontalin release rates increased attraction of Thanasimus spp. to seudenol. In a laboratory olfactometer assay, a combination of frontalin and seudenol released at rates comparable to those of a solitary, mining female arrested walking male eastern larch beetles whereas either compound alone did not. Insights into the eastern larch beetle's chemical ecology will improve understanding of cues in host and mate location that may be exploited for management.