RESPONSE OF THE WESTERN BALSAM BARK BEETLE, DRYOCOETES-CONFUSUS SWAINE (COLEOPTERA, SCOLYTIDAE), TO HOST TREES BAITED WITH ENANTIOSPECIFIC BLENDS OF EXO-BREVICOMIN AND ENDO-BREVICOMIN

The response of the western balsam bark beetle, Dryocoetes confusus Sw aine, to subalpine firs, Abies lasiocarpa (Hook.) Nutt., baited with ( +/-)-exo-brevicomin (EXOB) or 9:1 blends of EXOB and endo-brevicomin ( ENDOB), in two chiral combinations: (+):(+/-) and (+):(+), was assesse d in a heavily infested stand in British Columbia. Unbaited control tr ees were not attacked, and the proportion of mass-attacked baited tree s was similar for all other treatments. However, trees baited with the (+):(+) blend had the highest number of attacks per square metre, and they were also surrounded by the most attacked trees. The (+):(+/-) b lend was intermediate in attractancy, and (+/-)EXOB was the least attr active bait. Pheromone-based management of D. confusus infestations ma y be more effective with the 9:1 blend of (+)EXOB:(+)ENDOB than with t he previously used (+/-)EXOB baits.