Toxicity of pesticides against the diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Diamond back moth (DBM), Plutella xylostella (L.), an important pest of cole crops has developed resistance to almost all the groups of insecticides. Northeastern region of India uses relatively less quantity of pesticides for pest management of pests. Hence in vitro efficacy and co-toxicity of profenofos 50EC, cypermethrin 10EC, indoxacarb 14.5% and chlorpyrifos 20EC were evaluated using leaf dip bioassay on the field collected DBM populations. Indoxacarb 14.5% (LC₅₀ 20 ppm) was found to be the most effective, while the binary mixture of profenofos + chlorpyrifos and cypermethrin + chlorpyrifos (tested for all three combinations- 1:1, 1:2 and 2:1), showed synergistic effects. The results serve to promote use mixtures of insecticides having different mode of action.