Widely separated pheromone release sites for disruption of sex pheromone communication in two species of lepidoptera

Experiments were conducted to determine the efficacy of synthetic pheromone components ill causing disruption of attractancy of males of 2 moth species to females used as bait in traps in the centers of large field plots. For beet armyworm, Spodoptera exigua (Hubner) (Noctuidae), in tomatoes and Platynota stultana (Walsingham) (Tortricidae) in both peaches and table grapes, large, widely spaced (20 m apart) evaporators in 1-ha plots gave disruption equivalent to that provided by smaller, more closely spaced (5.5 m apart) evaporators, as long as the release rates in both cases were adjusted to the same level, approximate to 0.9 mg/ha/d. When evaporators releasing the same total amounts of components per hectare were spaced 100 m apart in 25-ha plots, a reduction in the efficacy of communication disruption was noted. Evaporators releasing approximate to 0.9 mg of pheromone components per hectare day and spaced at 5.5-m intervals around the perimeters only of 1- or 4-ha plots communication disruption of S. exigua in tomatoes and P. stultana in grapes and peaches equivalent to that provided by evaporators releasing the same amount of components per hectare pel. day and uniformly distributed at 5.5-m spacings within 1-ha plots. When evaporators releasing the same amount of components per hectare per day were spaced at 5.5-m intervals around the perimeters only of 16-ha plots, a reduction in communication disruption efficacy was also noted. It was calculated that evaporators releasing approximate to 0.9 mg of pheromone components per hectare per day could be separated from each other and from centrally located female-baited traps by up to 100 m before a lessening of communication disruption was obtained. Mechanical devices, which we call puffers, releasing pheromone components at 840 mg/ha/d, spaced at 40-m intervals around perimeters only of 16-ha plots, and separated from female-baited monitoring traps by 200 m, provided complete disruption of communication of S. exigua in tomatoes and P. stultana in grapes and peaches.