Baseline Susceptibility of Diamondback Moth Plutella xylostella L (Lepidoptera: Plutellidae) to Chlorantraniliprole 18.5 SC in Tamil Nadu

The baseline susceptibility of diamondback moth Plutella xylostella L to chlorantraniliprole 18.5 SC showed that, median LC₅₀ of chlorantraniliprole against diamondback mothlarvae for F₁ population was 20.06 ppm and LC₉₅ was 835.68 ppm whereas the LC₅₀ of F₂₅ population was 0.91 ppm and LC₉₅ was 23.11 ppm. The susceptibility increased up to F₂₂ population without exposure to insecticides. The susceptibility index (SI) after F₂₅ generation over F₁ generation was 22.02 and 36.15 based on LC₅₀ and LC₉₅ respectively. Based on LC₉₅ of F₂₅population, a tentative discriminating dose (DD) was fixed as 23.00 ppm. Among the insecticides viz., chlorantraniliprole 18.5 SC at 23 ppm, spinosad 2.5 SC at 12 ppm, emamectin benzoate 5 SG at 2 ppm and quinalphos 25 EC at 3 ppm tested, chlorantraniliprole 18.5 SC recorded low level of resistance with Udaghamandalam (53.83%), Coimbatore (58.83%) and Oddanchatram (64.00%) population, where as it was high in the case of emamectin benzoate, spinosad and quinalphos in the three regions.