Night observations on the cotton leafworm,Spodoptera littoralis: Reliability of pheromone traps for population assessment and efficacy of widely separated pheromone dispensers for mating disruption

Night observations on the cotton leafworm,Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), were conducted in pheromone-treated and untreated plots in which males, females, mating pairs on plants, and males caught in traps were collected. Results indicated that emergence of a new population was rapid (8-9 days) and that the number of virgin females and of mating pairs on plants reached a peak 5–6 days prior to that of males captured in pheromone traps. Males responded to pheromone traps most actively when the actual virgin female popution had already declined considerably. Dispensers adsorbed with(Z,E)-9,11-tetradecadienyl acetate and located 25 m apart, effectively reduced male captures in traps. However, the number of native mating pairs observed in the treated field during the night was not reduced. Few releasers at wide spacing, even with high amounts of the major pheromonal component, were ineffective in causing mating disruption ofSpodoptera littoralis.