Indian Journal of Plant Protection

A study was undertaken to evaluate toxicity of six biorational insecticides against Helicoverpa armigera (Hubner) under laboratory conditions. In leaf dip bioassay, on the basis of LC₅₀values against 3^rdinstar larvae of H. armigera, the order of toxicity of tested insecticides was emamectin benzoate > azadirachtin > spinosad > Bacillus thuringiensis > B. bassiana > HaNPV. The respective LC₅₀values for these insecticides were 0.00015, 0.00016, 0.00143, 0.00144 and 0.00277 per cent. The LC₅₀value for HaNPV was 2.39 x 10⁵PIB ml^-1. However, field doses calculated on the basis of LC₅₀were recorded with highest cumulative mortality of 3^rdinstar larvae in emamectin benzoate 5 SG (60.5%) and spinosad 45 SC (56.2%). For per cent pupation of surviving larvae, emamectin benzoate (22.3%) and spinosad (26.6%) showed significantly lowest pupation. Similar pattern was observed in pupal weight and healthy pupae. Maximum adult emergence was in control (90.0%) followed by HaNPV (37.2%). Azadirachtin 1 EC had the latent effect on hatchability of eggs laid by recovered adults by significantly reducing egg hatching. In ovicidal tests, lowest hatchability of eggs 72 h after treatment was recorded with spinosad (23.6%) and emamectin benzoate (30.5%) followed by B. thuringiensis (43.3%), B. bassiana (68.3%), HaNPV (70.4%) and azadirachtin (78.1%), respectively.