Pheromone Production, Attraction, and Interspecific Inhibition among Four Species ofIpsBark Beetles in the Southeastern USA

Abstract

Hindgut volatiles from attacking, unmated males ofIps avulsus, I. calligraphus, I. grandicollis, andI. piniwere analyzed by combined gas chromatography and mass spectrometry. Based on the quantitative identifications of hindguts and subsequent individual aerations, baits were formulated and a combined species-specific subtractive field bioassay was set up for the four bark beetle species. The bioassays were subtractive for the compounds identified in the hindgut analysis of each species, and volatiles identified in sympatric species were added as potential inhibitors alone and in combination. The trap catches from this bioassay revealed strong interspecific inhibition. The subtractive assays showed thatI. grandicollisandI. calligraphusshare (–)-(4S)-cis-verbenol as one pheromone component, while their second, synergistic pheromone component, (–)-(S)-ipsenol inI. grandicollisand (±)-ipsdienol inI. calligraphus, acts as an interspecific inhibitor to the other species.I. avulsusandI. piniwere found to have very similar production of hindgut volatiles, and both use ipsdienol and lanierone as synergistic pheromone components. No beetle-produced interspecific inhibitor was identified between these two species. Lanierone was found to be an interspecific inhibitor for bothI. calligraphusandI. grandicollis.