Toxicity of Insecticides to the Coccinellid Predators, Cryptolaemus montrouzieri Mulsant and Scymnus coccivora Ayyar of Papaya Mealybug, Paracoccus marginatus Williams and Granara De Willink

Abstract

Studies were carried out under laboratory conditions to assess the relative toxicity of insecticides viz., chlorpyriphos, dimethoate, profenophos, carbofuran, buprofezin, imidacloprid, thiamethoxam and spirotetramat against the non-target beneficials of papaya mealybug, Paracoccus marginatus (Williams and Granara de Willink) viz., Cryptolaemus montrouzieri Mulsant and Scymnus coccivora Ayyar. Among the test chemicals, thiamethoxam registered highest toxicity for C. montrouzieri grubs (LC₅₀ 156.65 ppm) and S. coccivora adults (LC₅₀–27.4968 ppm) while imidacloprid (LC₅₀–156.07 ppm) to Cryptolaemus adults. All the test insecticides viz., chlorpyriphos, dimethoate, profenophos, carbofuran, buprofezin, imidacloprid, thiamethoxam and spirotetramat were found safe to C. montrouzieri and S. coccivora based on selective toxicity ratio and sequential testing scheme. By probit substitution method, only chlorpyriphos and buprofezin were found safe to C. montrouzieri, while the rest of the insecticides were highly toxic to nontarget insects.