Reliability of a commercial trap to estimate population parameters of Japanese beetles, Popillia japonica, and parasitism by Istocheta aldrichi.

Commercial traps baited with floral compounds and a synthetic sex pheromone are commonly used to monitor the abundance of both sexes of the Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae). Trap captures can also provide estimates of parasitism proportion of adult beetles by Istocheta aldrichi (Mesnil) (Diptera: Tachinidae). However, whether these traps provide reliable assessments of demographic parameters and parasitism of Japanese beetle remains to be determined. In this study, we evaluated the reliability of baited traps to quantify sex ratios, parasitism proportions and body sizes of Japanese beetle populations by comparing trap captures and hand-picked samples on two ornamentals plant species (rose, Japanese knotweed) and one fruiting plant (raspberry). We found that the sex ratio, parasitism proportion and body size of beetles caught in traps were usually representative of what was present in surrounding vegetation, and any differences that we did observe between traps and hand sampling were inconsistent. Baited traps thus appear to be reliable tools for monitoring demographic parameters and parasitism levels of Japanese beetle. [ABSTRACT FROM AUTHOR]