Semiochemical-based host selection in bark beetles can be mediated by response to volatiles from host trees, nonhost trees, host trees infested by conspecifics and nonhost trees infested by heterospecifics. To determine if beetles were repelled by volatiles from heterospecifics, we collected airborne volatiles in Porapak-Q from four sympatric tree-killing bark beetles – the mountain pine beetle, Douglas-fir beetle, spruce beetle and the western balsam bark beetle. Gas-chromatographic electroantennographic detection analyses of these volatiles against the antennae of males and females of all four species revealed nine compounds to which the antennae of heterospecifics responded, but whose behavioural activity was unknown. Field experiments revealed four compounds that elicited behavioural activity. 1-octen-3-ol occurred in the volatiles of all four species and reduced catches of mountain pine beetles and Douglas-fir beetles in pheromone baited traps. The Douglas-fir beetle was significantly less attracted to its aggregation pheromone in the presence of a high dose of trans-verbenol or acetophenone found in the volatiles of mountain pine beetles. 3-2- Methyl-cyclo-hexenone, an antiaggregation pheromone of Douglas-fir beetles and spruce beetles significantly reduced the response of the mountain pine beetle to its aggregation pheromone. Spruce and western balsam bark beetles are under evaluation. This study suggests that perception of volatiles emitted by heterospecific beetles plays a role in the discrimination and selection of suitable hosts.
Species 1: Coleoptera Scolytidae Dendroctonus ponderosae (mountain pine beetle)
Species 2: Coleoptera Scolytidae Dendroctonus pseudotsugae (Douglas-fir beetle)
Species 3: Coleoptera Scolytidae Dendroctonus rufipennis (spruce beetle)
Keywords: host selection
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