Natural populations ofPlodia interpunctella(Hübner) andCadra cautella(Walker) were continuously exposed to synthetic sex pheromone for up to 99 days in 3 commercial peanut storage facilities. Mating activity, based on spermatophore counts, of females sampled at intervals from test buildings was not reduced in comparison to that of control females. It is emphasized that mating activity of wild females rather than inhibition of attraction of wild males to caged or tethered laboratory-reared females was the criterion of effectiveness employed in this study.