HOST COMPOUNDS AS KAIROMONES FOR THE WESTERN BALSAM BARK BEETLE DRYOCOETES CONFUSUS SW. (COL., SCOLYTIDAE)

Six compounds attractive to the western balsam bark beetle Dryocoetes confusus in laboratory bioassays were isolated by micropreparative gas chromatography from steam distilled phloem oil from subalpine fir, Ab ies lasiocarpa (Hook.) Nutt. In the bioassays (1S)-(-)-alpha-pinene, p -cymene, terpinolene, (+)-longifolene, (R)-(-)-myrtenal and transpinoc arveol were attractive at 1 mu g doses to both sexes of beetles. When combined with 10 pg doses of (+/-)-exo-brevicomin, all except terpinol ene increased the responses to exo-brevicomin in an additive manner. I n field experiments in British Columbia, none of the isolated compound s alone was attractive to D. confusus in multiple funnel traps. When p aired singly or together with a 9: 1 blend of(+)-exo- and (+)-endo-bre vicomin released at 0.2 mg per day, (1S)-(-)alpha-pinene and (R)-(-)-m yrtenal released at 12 and 2 mg per day, respectively, caused a signif icant increase in response by male beetles over the response to the 9: 1 blend alone. Myrtenal also increased the response of females. Becau se it is inexpensive and stable, (1S)-(-)-alpha-pinene could be used t o improve the sensitivity of pheromone-baited traps for monitoring D, confusus. However the pheromone blend alone is a highly efficacious tr ee bait, and host tree kairomones would probably not be needed in bait s used to manipulate D. confusus infestations.