Biological effects of azadirachtin on Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) fed on cotton and artificial diet

Abstract Neonates and second instars of Helicoverpa armigera (Hübner) were fed for 4 days on potted cotton plants (Gossypium hirstum L.) sprayed with formulated neem (Azadiracta indica A. Juss.) extract (3% azadirachtin emulsifiable concentrate). High mortality of larvae was observed on both treated plants and controls. Surviving larvae were transferred to an untreated artificial diet to assess the physiological effects caused by postdigestion of azadirachtin‐treated cotton. Growth retardation, including reduced larval and pupal weight and prolongation of development occurred in all treatments. Growth inhibition by azadirachtin was dose‐dependent. Physiological effects found in larvae fed on the artificial diet included difficulty in moulting between various instars, formation of larval–pupal intermediates and abnormal pupae. The present study indicates a potential for field control of H. armigera by using neem. High losses of larvae while feeding on cotton in controls are discussed.