International Journal of Plant & Soil Science

Use of synthetic insecticides for the management of fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith) for a longer period will led to development of insecticide resistance. Identification of an eco-friendly synergistic agent to enhance the toxicity potential and reduced pesticide use as well become mandatory in due process. Hence the present study was formulated to find the single and combined toxicity of chlorantraniliprole and Bacillus thuringiensis (Bt) against the 2^nd and 3^rd larval instars of S. frugiperda. Single toxicity of chlorantraniliprole against 2^nd and 3^rd larval instars were 0.87 and 1.52 ppm (LC₂₅); 4.08 and 6.50 ppm (LC₅₀), respectively. With respect to Bt, single toxicity against 2^nd and 3^rd larval instars were 474.39 and 693.48 ppm (LC₂₅); 1008.62 and 1228.62 ppm (LC₅₀), respectively. Combination effect of chlorantraniliprole with Bt revealed that 2^nd instar of FAW showed supplemental synergism at LC₅₀ of chlorantraniliprole + LC₂₅ of Bt. In the case of LC₅₀ of chlorantraniliprole + LC₅₀ of Bt_, LC₂₅ of chlorantraniliprole + LC₅₀ of Bt and LC₂₅ of chlorantraniliprole + LC₅₀ of Bt combinations, they showed sub additive synergism. In 3^rd instar larvae, the combined toxicity results were similar for all the combinations of chlorantraniliprole + Bt except LC₂₅ of chlorantraniliprole + LC₅₀ of Bt where it showed an antagonistic synergism. Activity of Carboxyl Esterase (CarE), Mixed Function Oxidase (MFO) and Glutathione-S-Transferase (GST) were found to be lesser in chlorantraniliprole LC₅₀ + Bt LC₂₅ combinations than single toxicity treatments. Therefore, combined use of chlorantraniliprole with Bt at LC₅₀ of chlorantraniliprole + LC₂₅ of Bt had supplemental synergism on fall armyworm under laboratory condition.