Bioefficacy of some organophosphate and synthetic pyrethroid insecticides against Henosepilachna vigintioctopunctata Fabricius

The contact toxicity of three OP insecticides was investigated against full grown grubs (average initial weight = 0.017 g/grub) of epilachna beetle by atomization and topical application (using microapplicator syringe) methods. In atomization method, quinalphos was 2.0 and 1.42 times more toxic (LC₅₀ = 0.0001 and 0.00007%) than the equitoxic profenofos and chlorpyriphos (0.0002 and 0.0001%) at 24 and 72 HAE, respectively. In topical application method, the order of toxicity at 24 and 48 HAE was quinalphos = chlorpyriphos (LD₅₀ =0.02 and 0.02 μg/grub) > profenofos (0.05 and 0.04 μg/grub), respectively. In another experiment, the contact toxicity of five SP insecticides was determined against full grown grubs of epilachna beetle by atomization and topical application (using microapplicator syringe) methods. In atomization method, the order of toxicity at 24 HAE was cypermethrin = alphamethrin (LC₅₀ = 0.00008%) > deltamethrin = bifenthrin (0.0001%) > lambda-cyhalothrin (0.0003%), and at 48 HAE it was cypermethrin = alphamethrin (0.00007%) > bifenthrin (0.0001%) > lambda-cyhalothrin (0.0002%). In topical application method, the order of toxicity at 24 HAE was lambda-cyhalothrin (LD₅₀ = 0.004 μg/grub,) > alphamethrin (0.007 μg/grub) > deltamethrin (0.009 μg/grub) > bifenthrin (0.01 μg/grub) > cypermethrin (0.02 μg/grub); at 36 HAE it was lambda-cyhalothrin (0.004 μg/grub) > alphamethrin (0.006 μg/grub) > deltamethrin = bifenthrin (0.008 μg/grub) > cypermethrin (0.01 μg/grub).