Study was conducted to test four insecticides, profenofos, emamectin benzoate, λ-cyhalothrin and lufenuron against field populations of Plutella xylostella and Spodoptera litura at different larval instars during 2010-11. The field populations collected from Rawalpindi and Taxila cauliflower fields was tested using leaf dip bioassay method under laboratory conditions. Tested restuls showed that emamectin benzoate was the most toxic insecticide for both P. xylostella and S. litura. However, profenofos was the second most toxic insecticides to different larval instars of S. litura and λ-cyhalothrin to P. xylostella. High LC50 values for lufenuron for this limited time exposure might be due to its slow acting as chitin synthesis inhibitor. Emamectin benzoate can be suggested as the most effective insecticides against both field populations along with profenofos and λ-cyhalothrin.
Key words: Spodoptera litura, Plutella xylostella, comparative toxicity, mode of action, age-dependent
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