Baseline Susceptibility and Resistance Monitoring of Pyridalyl 10 EC against Plutella xylostella L. (Lepidoptera: Plutellidae) in Tamil Nadu, India

In vitro studies were conducted to assess the baseline toxicity of pyridalyl 10 EC against Diamondback moth, Plutella xylostella collected from four major cabbage and cauliflower growing tracks in Tamil Nadu. The LC50 and LC95 values of Pyridalyl 10 EC from F1 to F15 generations declined from 2.528 to 0.447 ppm and 14.978 to 2.235 ppm respectively. The susceptibility index to pyridalyl was 5.655 based on LC50 and 6.702 based on LC95. With regard to number of generation required for ten-fold decrease in LC50 was 19.934. Considering the F15 population of P. xylostella as the most susceptible, the tentative discriminating dose arrived was 2.235 ppm. Resistance monitoring studies of P. xylostella across locations viz. Coimbatore, Hosur, Ooty, and Oddanchatram indicated that the per cent resistance ranged from the lowest of 2.008 ppm in Oddanchatram to the highest of 3.696 ppm in Hosur. The Pyridalyl 10 EC reflected the highest resistance ratio of 8.268 fold in Hosur field population and the lowest resistance ratio of 4.492 fold in Oddanchatram field population.