Measuring the effective sampling area of a pheromone trap for monitoring population density of southern pine beetle (Coleoptera: Scolytidae)

Multifunnel traps baited with frontalin and turpentine have been used to investigate dispersal of southern pine beetles, Dendroctonus frontalis Zimmermann, and are routinely used in the southern United States to monitor population trends of this serious forest pest. However, there is no quantitative data on the effective sampling area of these traps that would allow us to convert numbers of beetles caught in a trap to their absolute population density (numbers per hectare). We conducted field studies to determine the effective sampling area of the multifunnel trap. Using field releases of marked beetles, we estimated how the probability of capture declines with distance between the trap and the release point. The estimated relationship between the capture probability and distance is then translated into the effective sampling area. The effective sampling area for the multifunnel trap was estimated as approximate to 0.1 ha. Our results also indicate that the capture efficiency of a trap declines with increased density of host trees around the trap. We discuss our findings in the context of previous studies that measured attraction to pheromone traps in other species of bark beetles and in the gypsy moth.