Development of Water Dispersible Powder (WDP) Formulation of Bacillus thuringiensis var. kurstaki and evaluation against Helicoverpa armigera (Hubner)

Thirty two recipes of 7% WDP formulation of Bacillus thuringiensis var. kurstaki (HD-1) were prepared in the laboratory using eight carriers viz barium sulphate, bentonite, dolomite, fuller's earth, kaolinite, precipitate of silica, pyrophyllite and talc, two dispersing agents viz lignosulphonate (LS) and naphthalene sulphonate condensate (NSC) and two wetting agents viz sodium lauryl sulphate (SLS) and linear alkyl benzene sulphonate (LABS). The LC₅₀ values ranged from 0.025–0.154% against neonates of Helicoverpa armigera. Recipe containing grecipitata of silica was found more effective (LC₅₀ 0.025%) compared to commercial formulation Halt 5%WP (LC₅₀ 0.043). Physico chemical properties of the carriers influenced the bioactivity of Bacillus thuringiensis in WDD formulation.