Bio-efficacy, persistence and residual toxicity of different insecticides against girdle beetle, Obereopsis brevis (Swedenborg) infesting soybean

Abstract

An investigation was undertaken to study the bio-efficacy, persistence and residual toxicity of different insecticides viz., chlorantraniliprole 0.004 per cent, ethion 0.100 per cent, triazophos 0.050 per cent, indoxacarb 0.010 per cent, emamectin benzoate 0.001 per cent, quinalphos 0.050 per cent and profenophos 0.100 per cent against Obereopsis brevis (Swedenborg) infesting soybean at the Research Farm of Department of Agril. Entomology, College of Agriculture, Latur (MS). The result revealed that all the insecticidal treatments were significantly superior over untreated control in minimizing the per cent plant infestation due to O. brevis. Among the treatments, chlorantraniliprole 0.004 per cent was found to be the most effective insecticide in minimizing infestation due to O. brevis on soybean (6.10 and 3.77 per cent per mrl) followed by ethion 0.100 per cent (6.52 and 4.58 per cent per mrl), triazophos 0.050 per cent (7.33 and 4.60 per cent per mrl), indoxacarb 0.010 per cent (7.44 and 4.63 per cent per mrl), emamectin benzoate 0.001 per cent (7.44 and 5.11 per cent per mrl), quinalphos 0.050 per cent (7.59 and 5.33 per cent per mrl) and profenophos 0.100 per cent (8.55 and 5.99 per cent per mrl) after first and second sprays, respectively. The highest grain yield was achieved by chlorantraniliprole 0.004 per cent (34.87 q per ha) while quinalphos 0.050 per cent (1:19.72) documented highest incremental cost benefit ratio. The results on residual toxicity of different insecticides against O. brevis infesting soybean indicated that chlorantraniliprole 0.004 per cent and ethion 0.100 per cent illustrated highest persistent toxicity index (PT) (851.86 and 817.14 and; 833.80 and 827.96, respectively) and LT50 values (6.48 and 6.14 and; 6.48 and 6.10 days, respectively) against early instar grubs of O. brevis after first and second sprays as compared to the other insecticides.