Relative toxicity of three synthetic pyrethroids and endosulfan to susceptible strain of Helicoverpa armigera (Hubner) from Hissar (India)1

Relative toxicity of three synthetic pyrethroids and endosulfan was evaluated against 1 to 2-day old larvae of susceptible strain of Helicoverpa armigera using dry film technique. On the basis of LC50 values, the order of toxicity was: deltamethrin > cypermethrin > fenvalerate > endosulfan. The former three were respectively 34.93, 20.10 and 5.28 times as toxic as endosulfan (0.00008). Very low LC50 values, viz., deltamethrin (0.00000229), cypermethrin (0.00000398) and fenvalerate (0.00001545) indicated that Hissar strain of H. armigera was quite susceptible and resistance was not evident as in other parts of India.