DISPLACEMENT AND AGGREGATION OF MOUNTAIN PINE BEETLES, DENDROCTONUS-PONDEROSAE (COLEOPTERA, SCOLYTIDAE), IN RESPONSE TO THEIR ANTIAGGREGATION AND AGGREGATION PHEROMONES

Deployment of verbenone release devices at 10-m centres significantly reduced the percent of available lodge (Pinus contorta Dougl. var. latifolia Engelm.) that were mass attacked by mountain pine beetles (Dendroctonus ponderosae Hopkins) in 50 x 150 m subplots flanked on each side by identical subplots, regardless of whether the flanking plots were baited with tree baits or left untreated. Verbenone treatment also increased the percent of unsuccessful attacks (<31.25 attacks/m2) in the central subplot compared with when the central subplot was left untreated. Tree baits, composed of trans-verbenol, exo-brevicomin, and myrcene, applied in flanking subplots did not affect significantly the percent of trees mass attacked nor the attack density. However, assuming a 2:1 expected ratio of attacks in the two flanking subplots over the central subplot, chi2-tests indicated that the attack distribution was consistently altered only when both verbenone and aggregation pheromones were applied. This study suggests that a ''push-pull'' tactic using aggregation and antiaggregation pheromones may be feasible for managing this destructive pest.