In leaf disc choice assays and topical application experiments, the neem (Azadirachta indica) limonoids azadirachtin, salannin, deacetylgedunin, gedunin, 17-hydroxyazadiradione and deacetylnimbin were found to be potent antifeedants and growth inhibitors to the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Azadirachtin was most potent in both respects. Gross dietary utilisation (efficiency of conversion of ingested food) of H. armigera was also decreased following topical application as well as after treatment in the diet. Growth inhibition in topically treated H. armigera may be primarily attributed to decreased food intake. The antifeedant and growth-inhibitory effects of the neem limonoids are discussed.
