Baseline toxicity of diamide group of insecticides against diamondback moth, Plutella xylostella L.

A study was carried out to assess the susceptibility of Plutella xylostella in different locations of Tamil Nadu against the diamide group of insecticides. The LC50 values were checked for all the populations. The LC50 values of the susceptible population for flubendiamide 20WG, chlorantraniliprole 18.5SC and cyantraniliprole 10.26OD were 0.021 mg ml-1, 0.048 mg ml-1 and 0.007 mg ml-1, respectively. Cyantraniliprole 10.26OD proved to be the best in toxicity to all the geographic population viz., Coimbatore, Ooty, Oddanchatram, Krishnagiri and Theni compared to chlorantraniliprole 18.5SC and cyantraniliprole 10.26OD. The resistant ratio was also significantly low compared to chlorantraniliprole and flubendiamide (1.43, 1.71, 2.00, 2.43, 1.57) in Coimbatore, Ooty, Oddanchatram, Krishnagri and Theni, respectively). The resistant ratio was higher in flubendiamide 20WG (5.143 to 8.619) and chlorantraniliprole 18.5SC (2.167 to 3.562) than cyantraniliprole 10.26OD in all five different locations.