Comparative efficacy of microbial, botanical and chemical insecticides against lepidopteran pests in castor.

Abstract

Studies were conducted to evaluate the efficacy of microbial [combination formulation of Beauveria bassiana + Bacillus thuringiensis var. kurstaki (Btk), indigenous and commercial formulations of Btk], botanical (karanj oil and neem seed kernel extract) and chemical (profenofos) insecticides against semilooper (Achaea janata) and capsule borer (Conogethes punctiferalis) in castor. In laboratory bioassay, Btk (Delfin®) @ 1g/L, combination formulation of B. bassiana + Btk @1.25 ml/L and 2 ml/L effected 100% mortality in third instar larvae of semilooper 48h after treatment as compared to 100% mortality by profenofos @ 1ml/L at 24h after treatment. Btk @1g/L and combination formulation of B. bassiana + Btk @ 2ml/L were found effective in reducing semilooper population (97.5% and 91.0% larval reduction over untreated control) and at par with profenofos (100% reduction over control) in field trial. However, their efficacy in reducing capsule borer damage (39.2 and 27.8% reduction over control, respectively) and seed yield obtained (1897 and 1836 kg/ ha, respectively) was significantly lower than profenofos (53.6% reduction in capsule damage and seed yield of 2036 kg/ha) but superior over botanicals. Cocoons of larval parasitoid of semilooper, Snellenius (Microplitis) maculipennis were more in numbers in microbial and botanical treatments compared to profenofos. The microbial formulations viz., combination formulation of B. bassiana + Btk and Btk can be opted for inclusion as a component in the Integrated Pest Management in castor.