Evaluation of two repellent semiochemicals for disruption of attack by the mountain pine beetle, <i>Dendroctonus ponderosae</i> Hopkins (Coleoptera: Scolytidae)

Abstract

When released from attractant-baited multiple-funnel traps, 3-methyl-2-cyclohexen-1- one (MCH) reduced catches of male and female mountain pine beetles, Dendroctonus ponderosae Hopkins, by 67.4% and 71.8%, respectively. 2-Phenyl ethanol reduced the respective catches by 96.6% and 95.1%, but only verbenone and all three compounds together reduced catches to levels no different from those in unbaited control traps. In another experiment, all three binary combinations of the above compounds, plus the ternary combination, reduced catches of both sexes by >96%. In comparable tree protection experiments near Princeton BC, MCH and 2-phenyl ethanol alone and together significantly reduced the percentages of pheromone-baited lodgepole pines that were attacked by 16.0%, 33.3% and 40.0%, respectively, but verbenone alone totally protected baited trees, and many trees within 5 m of them, from attack. In identical experiments near Prince George BC, where mountain pine beetle populations were much higher, adding MCH, 2-phenyl ethanol or both together to verbenone did not cause attack to be reduced significantly beyond that achieved by verbenone alone. Our results confirm that 2-phenyl ethanol is an antiaggregation pheromone for the mountain pine beetle, and that MCH is an interspecific synomone. However, because neither was as effective as verbenone in protecting pheromone-baited trees from attack, and adding either or both to verbenone did not improve protection, neither compound warrants further consideration as a potential tool for operational disruption of attack.