Sampling range and range of attraction of Dendroctonus pseudotsugae pheromone-baited traps

Two mark-recapture experiments and a trap interference experiment were conducted to determine the sampling range and range of attraction, respectively, of Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae) pheromone-baited traps in northern Idaho. To determine the sampling range, either live beetles or logs containing brood were marked with one of four colors of fluorescent powder. Colored beetles or logs were placed along transects oriented away from a central pheromone-baited trap at distances of 50, 100, 200, and 300 m. A release distance of 400 m was added to one mark-recapture experiment during the 2nd year. To determine the range of attraction, a trap interference study was conducted. For this experiment, groups of three traps were oriented in equilateral triangles with distances of 50, 100, 200, and 300 m between the three traps. Distances between traps were changed daily to allow for adequate replication. Mark-recapture studies indicated that most D. pseudotsugae were recaptured from distances less than or equal to 200 m from the pheromone-baited trap. On average, 95% of beetles recaptured were males. Results of the trap interference experiment provided no insight into the range of attraction of D. pseudotsugae pheromones. Natural resource managers should attempt to place pheromone-baited suppression traps within 200 m of target D. pseudotsugae populations. Also, to minimize undesirable beetle-caused tree mortality, traps should be placed as far as possible from live trees that managers wish to protect.