Evaluation of two pheromone baits for containment and concentration of attack by the western balsam bark beetle, Dryocoetes confusus (Coleoptera: Curculionidae)

In past studies, the greatest response by the western balsam bark beetle Dryocoetes confusus Swaine (Coleoptera: Scolytidae) to traps and baited trees was obtained with blend of (+)-exo- and (+/-)-endo-brevicomin, which mimic the natural male-produced aggregation pheromone. We conducted a tree-baiting experiment to determine whether low-release enantiospecific blends 9:1 (+) exo-brevicomin:(+)-endo-brevicomin, or 9:2 (+)-exo-brevicomin: (+/-)-endo-brevicomin released at 0.3, 0.1, or 0.03 mg/day could compete with or improve the efficacy of the standard (+/-)-exo-brevicomin bait released at 1.2 mg/day. In this experiment, the standard and experimental baits were almost 90% effective in inducing attack by D. confusus. Two subsequent 9-ha block experiments compared the ability of the standard and 9:2 (+)-exo-brevicomin:(+/-)-endo-brevicomin baits to contain and concentrate infestations before harvesting. Again, both baits were equally effective as potential stand management tools based on almost 100% attack on baited trees, green-to-red tree ratios between 3:1 and 5:1, and redistribution of the majority of attack around baited rather than red trees from which beetles could emerge. We recommend that the standard bait continue to be offered commercially for treatment of stands infested by D. confusus.