Effect of some important insecticides on the adults of Coccinella septempunctata Linn. predating on different aphid species

The safety margin of twenty-four insecticides for the adults of aphid predator, Coccinella septempunctata Linn. was determined by bioassay technique. On the basis of LC₅₀ (values given in parentheses), the relative toxicity of different insecticides in the descending order was: lambdacyhalothrin (0.0009212), decamethrin (0.00219), alphamethrin (0.002548), dimethoate (0.00424), cypermethrin (0.005367), monocrotophos (0.00755), phosphamidon (0.007875), fenitrothion (0.0129), fenpropatbrin (0.01329), methyl parathion (0.01419), dichlorovos (0.01616), malathion (0.02376), carbaryl (0.02595), polytrin (0.02667), fenvalerate (0.0335), quinalphos (0.03352), profenofos (0.03372), pyrethrin (0.07183), trebon (0.08638) and methyl demeton (0.1226). However, the least toxic insecticides were lindane, endosulfan, aphidan and menazon, which gave less than 50 per cent mortality even at 1per cent concentration. A comparison of relative resistance values of adults of C. septempunctata vis-a-vis important aphid pests, viz, Lipaphis erysimi, Dactynotus carthami, Aphis craccivora and Myzus persicae indicated that out of the various insecticides tested, methyl demeton, lindane, endosulfan and aphidan exhibited a very high safety margin for the predatory adults, being at the same time most effective and commonly used against these various aphid species.