Relative Toxicity of Newly Introduced Insecticides against Sucking Insect Pests of Transgenic Bt Cotton

The efficacy of some newly introduced insecticides viz. tolfenpyrad 15EC, spiromesifen 24SC, pyriproxyfen 10EC, diafenthiuron 50WP, ethion 50EC against whitefly and dinotefuran 20SG, tolfenpyrad 15EC, flonicamid 50WG, imidacloprid 17.8SL and thiamethoxam 25WG against whitefly and jassid on Bt cotton evaluated during 2011 is reported. At 24 h, the LC₅₀ for tolfenpyrad, diafenthiuron, ethion and spiromesifen were 0.182, 0.063, 0.069 and 0.026% respectively against whitefly populations collected from Ludhiana; the order of toxicity being spiromesifen > diafenthiuron > ethion > tolfenpyrad. The LC₅₀ values for tolfenpyrad, diafenthiuron and pyriproxyfen at 48 h were 0.34, 0.034 and 0.051% respectively, the order of toxicity being diafenthiuron > pyriproxyfen> tolfenpyrad. Similarly, the LC₅₀ for flonicamid, thiamethoxam, tolfenpyrad, imidacloprid and dinotefuran at 24 h were 0.014, 0.014, 0.023, 2.631 and 0.006% respectively against jassid population collected from Ludhiana; the order of toxicity being dinotefuran > flonicamid=thiamethoxam > tolfenpyrad > imidacloprid. The most toxic insecticides against jassid populations after 48 h bioassay were flonicamid 50WG and thiamethoxam 25WG.