Capillary tube evaporators arrayed in grids in tomato, alfalfa, and cotton fields released into the air four previously identified pheromone components, either separately or in various blend combinations, of the beet armyworm,Spodoptera exigua(Hübner). Disruption of pheromone communication in this species was measured by the decrease in the numbers of male moths orienting to female moths that were used as bait in traps in the centers of the grids. The only pheromone component that appeared essential to provide disruption of communication was (Z,E-9,12-tetradecadienyl acetate. Research comparing grids equipped with evaporators of four different sizes, each size spaced at three separations in the field, indicated that the spacing between evaporators, up to 4.6 m apart, was not the most critical factor determining the amount of disruption obtained. Rather, the most important factor appeared to be evaporator size; the largest evaporators, releasing 25 μg of the pheromone component per day, provided the highest amount of disruption, even when spaced in the field at the maximum tested separation. TheS. exiguapheromone component, (Z,E)-9,12-tetradecadienyl acetate, did not disrupt communication between males and females of the tomato pinworm,Keiferia lycopersicella(Walsingham), and theK. lycopersicellapheromone, (E)-4-tridecenyl acetate, did not disrupt communication between the sexes ofS. exigua.