Effect of Carriers on the Efficacy of Bacillus thuringiensis Var. Kurstaki (HD-1) formulations

Abstract

Effect of carriers on the efficacy of new wettable powder (WP) formulations of Bacillus thuringiensis var. kurstaki (HD-1) was evaluated at Division of Entomology, Indian Agricultural Research Institute, New Delhi during 2006-2008. Sixteen wettable powder (WP) formulations were developed by using eight carriers viz., barium sulphate, bentonite, dolomite, fuller earth, kaoline, talc, precipitate of silica and pyrophyllite. Six physico-chemical properties i.e. bulk density, carrier reaction (pH), cation exchange capacity; moisture content, sorptivity and specific surface area of the carriers were studied. The formulations were evaluated against III^rd instar larvae of Helicoverpa armigera (Hubner) and based on the LC₅₀ values; formulation-7 (0.018%) and formulation-15 (0.015%) were found to be highly effective. The formulation-7 and formulation-15 contained precipitate of silica as carrier and we report that and it proved to be best carrier for preparation the WP formulation of B. thuringiensis var. kurstaki.