A microencapsulated formulation of disparlure was aerially broadcast at rates of 5.0 and 15.0 g/ha onto 16-ha test plots. Laboratory-reared (lab) and field-collected (wild) gypsy moth (Porthetria disparL.) pupae were placed in these plots at densities ranging from 2 pr/ha to 32 pr in an area of ca. 700 m2. After oviposition, or at the end of a 10-11 day test period, female adults and/or their egg masses were recovered for assessment of mating success.Reduction of mating success was statistically significant in all treatments except in plots with only 2 pr wild insects/ha; mating success in control plots at this density was very low. Recovery rates of females from lab pupae were higher than those from wild pupae. In several tests with lab and wild insects, female infertility rates exceeded the 90% level previously proposed as necessary to cause population reduction in the next generation. Suppression of mating was still evident in tests initiated as long as 6 wk after pheromone application.Lab insects are suitable indicators of results to be obtained with wild gypsy moths in identical tests. Because of behavioral and physiological differences between these 2 types of insects, however, wild insects must be used for final definitive tests.