Joint Action of Cypermethrin and Profenofos against Helicoverpa armigera

Studies on the joint toxic action of cypermethrin and profenofos on the insecticide resistant population of Helicoverpa armigera indicated that cypermethrin (with an LD₅₀ of 2.0105 mg insect⁻¹) and profenofos (with an LD₅₀ of 0.9757 mg insect¹) when mixed at different ratios of 1:10, 1:5, 1:1 and 5:1, respectively and applied on the larvae of 30–40 mg weight range, the LD₅₀ value of the mixture came down to 0.6814 (1:10), 0.4750 (1:5), 0.3031 (1:1) and 0.1919 (5:1) mg insect⁻¹ indicating co-toxicity coefficient values of 150.22, 224.68, 433.44 an 890.06, respectively, for the mixtures. This also indicated that cypermethrin was more potentiated by the profenofos while profenofos was less potentiated by cypermethrin.