EFFECT OF INSECT PREDATORS AND A PYRETHROID INSECTICIDE ON COTTON APHID, APHIS-GOSSYPII GLOVER, POPULATION-DENSITY

Cotton plants enclosed in predator exclusion cages were compared with uncaged plants to examine the impact of predaceous arthropods on cotto n aphid, Aphis gossypii Glover, populations. Effects of the pyrethroid insecticide cyhalothrin (Karate(R)) on A. gossypii population develop ment also were examined. Rapid increases in cotton aphid numbers, resu lting in significant yield reductions, occurred on plants when predato rs were excluded. These aphid populations declined only after exceedin g the carrying capacity of the plants. Cotton aphid infestations on un caged plants and on plants to which predators were introduced or allow ed access were quickly controlled by naturally occurring predator popu lations. When predators were excluded, cotton aphid numbers increased faster and to higher levels on cyhalothrin treated plants than on untr eated plants. The more rapid increase in aphid populations was not due to the absence of predators, and was therefore attributed to a physio logical interaction between cyhalothrin and cotton leaves or cotton ap hids that resulted in increased aphid reproductive activity.