SECONDARY ATTRACTION IN THE WESTERN BALSAM BARK BEETLE, DRYOCOETES CONFUSUS (COLEOPTERA: SCOLYTIDAE)

Abstract

AbstractEvidence for secondary attraction in the western balsam bark beetle, Dryocoetes confusus Swaine, was obtained in laboratory bioassays and field experiments. Both sexes showed positive responses to volatiles of the host tree, Abies lasiocarpa (Hook.) Nutt., indicating that primary attraction is probably important in host selection by this species. Male beetles initiated attack and within 6 h produced an aggregation pheromone(s), which was present in frass and in pentane extracts of the abdomens of males excised from logs. Both sexes responded to the pheromone. Abdominal extract of unmated males which had bored into host bark for 14 days was still attractive. Pheromone production was induced by exposing males to host resin volatiles. Mating had no effect on male attractiveness, but induced females to produce an antiaggregation pheromone which, in laboratory bioassays, at least partially inhibited response to male attractant. The attractive volatiles from male-infested logs were successfully captured on Porapak Q®. The development of laboratory bioassay and pheromone extraction techniques indicates that a pheromone isolation program is feasible.