Efficacy of an Antiaggregation Pheromone for Reducing Douglas-Fir Beetle,dendroctonus Pseudotsugaehopkins (Coleoptera: Scolytidae), Infestation in High Risk Stands

The Douglas-fir beetle ( Dendroctonus pseudotsugae ) antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), was applied to stands at high risk for infestation. The MCH was applied in a bubble capsule formulation to plots ranging from 2.1 to 2.6 ha in size at rates of 45–76 g/ha. Catches of Douglas-fir beetles in attractant-baited Lindgren funnel traps located at the plot centers were significantly lower on MCH-treated plots compared with untreated plots. In contrast, catches of the most abundant predator, Thanasimus undatulus (Say), were unaffected by the MCH treatment. The percentage of Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco] trees ≥20 cm dbh that were mass attacked was significantly lower on treated plots (0.2%) compared with untreated plots (8.5%). MCH alone was effective in reducing the probability of Douglas-fir beetle infestations occurring in high risk stands.