Field tests were conducted to determine whether the insect sex pheromones gossyplure and prodlure could be used in the same trap to capture male pink bollworm moths andSpodoptera littoralismoths and to compare the efficiency of wet versus dry traps. Results showed conclusively that an antagonistic effect was produced by placing both pheromones in close proximity in the same or different traps and on the same or different dispensers; the effect was evident even with two traps located 0.5 meter apart. The antagonism was responsible for a permanent reduction in pink bollworm catches and a temporary reduction in captures ofS. littoralis. Dry open traps lined with 4% diazinon powder were superior to the standard widely used wet traps.