Natural Control of Helicoverpa armigera in Cotton: Assessment of the Role of Predation

Irreplaceable mortality of Helicoverpa armigera due to natural enemies was studied in cotton in western Kenya. Field populations of H. armigera were followed in three types of subplots: where crawling predators were suppressed, where both crawling and flying predators were suppressed and where predators were unaffected. Ants were the predominant crawling predators, whereas anthocorids were the predominant flying predators. H. armigera mortality from egg to late larval stage was very high (96.4-99.7%) and was greater in the second than in the first generation. Suppression of the different groups of predators did not increase the density of the pest. It is argued that the high level of background mortality obscured the role of predators. The possible role of host-plant condition on background mortality is discussed.