Insecticide resistance in diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Punjab

Abstract

The diamond back moth (DBM) Plutella xylostella (Linnaeus), a major destructive pests of brassica crops, is recurrently infesting vegetables in Punjab. It has led the farmers to frequently spray their crops with insecticides, but control failures occur with many insecticides. Hence this study with the objective to check whether resistance to insecticides could explain these failures. Populations of DBM from different locations viz., Amritsar, Ludhiana and Kapurthala were collected and toxicity of five insecticides viz., emamectin benzoate, spinosad, indoxacarb, chlorantraniliprole and cartap hydrochloride and a Bt formulation was evaluated. It was compared with its susceptible population, maintained for over 30 generations under laboratory conditions, using the standard leaf-disc dip technique. The susceptible population showed the maximum sensitivity to emamectin benzoate with lowest LC50 of 0.00003%, while it was minimum with cartap hydrochloride (0.00145%). Chlorantraniliprole was the most toxic against the field populations (LC50 was 0.00012- 0.00027%) followed by emamectin benzoate (0.00154–0.00336%), while cartap hydrochloride was the least effective. DBM population from Amritsar showed maximum resistance to all insecticides except indoxacarb, while the Ludhiana one was showing maximum resistance to all. Field populations exhibited maximum resistance to emamectin benzoate (51.3–112x) followed by cartap hydrochloride (26.33–52.84x), and minimum against chlorantraniliprole (2.4 to 5.4x). The results indicate that control failures were associated with resistance to some of the evaluated insecticides, reinforcing the need for resistance management strategies in vegetable growing areas of Punjab