Bioefficacy of some insecticides and mixed formulations against Spilarctia obliqua (Wlk.)

The contact toxicity of fenvalerate and fenpyroximate was determined against 3d old larvae of S. obliqua (mean larval weight = 0.0032 g) by atomization method. Fenvalerate (LC50 = 0.000037, 0.000023 and 0.000018%) was 112.05, 123.22 and 123.94 (RT) times more toxic than fenpyroximate (LC50 = 0.004146, 0.002834 and 0.002231%) at 24, 48 and 60 HAE, respectively. The contact toxicity of fenpyroximate, fenvalerate, ethion + cypermethrin and thiamethoxam + lambda-cyhalothrin was determined against 11d old larvae of S. obliqua (mean larval weight = 0.2243 g) by atomization method. Fenvalerate (LC₃₀ = 0.000046%) was 30.43 (RT) times more toxic than fenpyroximate (LC₃₀ = 0.0014%) at LC₃₀ 24 HAE. Fenpyroximate (0.01 & 0.005%) caused 50% mortality in 3.73 & 23.39 h and fenvalerate (0.002 & 0.0007%) in 3.01 & 8.60 h, respectively. The stomach and contact toxicity of fenvalerate and fenpyroximate was determined against 3d old larvae of S. obliqua (mean larval weight = 0.0032 g) by leaf dip method. Fenvalerate (0.0002 and 0.0001%) caused 30, 50, 90% mortality in 12.13, 19.55, 66.80 (0.0002%) and 14.30, 22.07, 64.18 h, respectively while fenpyroximate (0.009) caused 30, 50 and 90% mortality in 14.91, 22.38 and 60.78 h, respectively. Fenvalerate (LC50 = 0.00003%) was 64.83 (RT) times more toxic than fenpyroximate (LC50 = 0.001945%) at 48 HAE.