Combining Exclusion Techniques and Larval Death-rate Analyses to Evaluate Mortality Factors of Spodoptera Exigua (lepidoptera: Noctuidae) in Cotton

By combining pesticide exclusion and cage exclusion techniques, the efficacy of natural enemies in reducing populations of Spodoptera exigua (Hübner), the beet armyworm, larvae was effectively demonstrated. Larval collections added information about parasitism and disease, and when combined with data from insecticide treatments, demonstrated that differences in S. exigua population densities usually were due to the action of predators. Deathrate analyses demonstrated that much mortality due to parasitism was contemporaneous with death from predation. When predator populations were not reduced by insecticides, most indispensable natural mortality was due to predation. When predators were eliminated, and S. exigua populations reached outbreak levels, most larvae died from disease in 1989 and from parasitism in 1990.