Pheromone-Baited Traps for Dendroctonus pseudotsugae (Coleoptera: Scolytidae): Influence of Selected Release Rates and Trap Designs

Abstract

Several different aggregation pheromone release rates and trap designs were evaluated for trapping the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins. Frontalin:seudenol release rates of 160:80, 80:40, 40:20, 20:10, 10:5, and 1:0.5 mg/d, respectively, with a constant ethanol release rate of 88 mg/d at 24°C were tested in multiple-funnel traps. The highest Douglas-fir beetle catches occurred at release rates of 20:10 and 10:5 mg/d. There were significantly fewer catches at higher and lower release rates. The percentage of male Douglas-fir beetles increased significantly with increasing release rates up to a plateau at 80:40 mg/d. Catches of Thanasimus undatulus (Say) (Coleoptera: Cleridae), a predator, increased consistently with higher release rates. Multiple-funnel traps caught significantly more Douglas-fir beetles than slotted-panel traps for both total numbers and number per unit area of trapping surface. There was no difference between the 2 trap types in selectivity for Douglas-fir beetles relative to T. undatulus. Placing metal screens with 6- or 12-mm openings above the collection cup to filter intercepted insects or providing a strip of metal screen with 1.5-mm openings to serve as an escape route for predators from the collection cup in multiple-funnel traps resulted in capture of a significantly higher ratio of Douglas-fir beetles to predators. These results will contribute to the development of more efficient trapping programs to lessen the impact of Douglas-fir beetle outbreaks.