PHEROMONE-BAITED TRAPS FOR DENDROCTONUS-PSEUDOTSUGAE (COLEOPTERA, SCOLYTIDAE) - INFLUENCE OF SELECTED RELEASE RATES AND TRAP DESIGNS

Several different aggregation pheromone release rates and trap designs were evaluated for trapping the Douglas-fir beetle, Dendroctonus pseu dotsugae Hopkins. Frontalin:seudenol release rates of 160:80, 60:40, 4 0:20, 20:10, 10:5, and 1:0.5 mg/d, respectively, with a constant ethan ol release rate of 88 mg/d at 24 degrees C were tested in multiple-fun nel traps. The highest Douglas-fir beetle catches occurred at release rates of 20:10 and 10:5 mg/d. There were significantly fewer catches a t higher and lower release rates. The percentage of male Douglas-Br be etles increased significantly with increasing release rates up to a pl ateau at 80:40 mg/d. Catches of Thanasimus undatulus (Say) (Coleoptera : Cleridae), a predator, increased consistently with higher release ra tes. Multiple-funnel traps caught significantly more Douglas-fir beetl es 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 ship of metal screen with 1.5-mm openings to serve as an escape route for predators from th e collection cup in multiple-funnel traps resulted in capture of a sig nificantly higher ratio of Douglas-fir beetles to predators. These res ults will contribute to the development of more efficient trapping pro grams to lessen the impact of Douglas-fir beetle outbreaks.