ESTIMATING GYPSY-MOTH (LEPIDOPTERA, LYMANTRIIDAE) EGG MASS DENSITY USING MALE MOTHS CAPTURED IN PHEROMONE-BAITED, MILK-CARTON TRAPS

We attempted to develop an accurate and efficient means to estimate gypsy moth egg mass density or, alternatively, develop techniques to aid in prioritizing areas that might require egg mass sampling. Results indicate that it is possible to determine the probability of finding some level of egg mass density in the vicinity of a pheromone trap depending on the number of moths captured in that trap. A linear relationship was found between number of moths captured and gypsy moth egg mass density, but this relationship has little predictive value. Wing length of male moths collected in pheromone traps was used to estimate defoliation and male moth dispersal. Wing length of moths captured in pheromone traps was found not to be a reliable indicator of whether or not defoliation occurred. However, capture of small moths, which develop in defoliated areas, in traps located in nondefoliated areas indicated that these moths probably dispersed from other, defoliated areas. Capture of small moths may be useful to determine whether or not to initiate egg mass sampling at the trap location. An algorithm to interpret data from pheromone traps is presented. Trap data interpretation involves use of male wing length, number of moths captured, and defoliation maps. The information obtained from the algorithm will be most useful to evaluate an area for the need to conduct egg mass sampling. Forest managers can evaluate the risk of failing to detect high egg mass density with the need to allocate sampling resources optimally.