Rhizobacteria isolated from cotton roots exhibiting antagonism towards seedling blight and leaf blight of cotton were tested for their efficiency against the insect pest American bollworm (Helicoverpa armigera). The bioformulation developed using Bacillus subtilis (isolate DGL9) + chitin was found to be detrimental to the developmental stages of H. armigera (larva, pupa and adult) by causing larval mortality, pupal and adult malformation with reduced adult emergence. Generally, the larvae exhibited antifeeding behaviour when fed on bolls collected from rhizobacterial treatments. Hence, the developmental stages were altered leading to early pupation. Further, the efficacy of the isolate DGL9 was confirmed by culturing the bacteria in a suitable medium and incorporating the cell suspension and supernatant obtained form the broth culture in larval diet. The larvae fed to the diet exhibited defective developmental stages which was more significant in case of diet incorporated with supernatant. The percentage of pupal malformation, adult emergence and adult malformation was high at 96 h of incubation with the supernatant.
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