Relative toxicity of insecticides against cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera:Pseudococcidae) and its fortuous parasitod Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae)

Nineteen insecticidal formulations from 10 groups of insecticides were evaluated for their relative toxicity against cotton mealybug Phenacoccus solenopsis Tinsley and its fortuous parasitoid Aenasius bambawalei Hayat. Insects were exposed to cotton leaves dipped in insecticidal solutions and their mortality was recorded at 24-h intervals. Within 24 h of exposure, Quinalphos, Chlorpyriphos, Thiamethoxam and Profenophos have detrimental effect on both P. solenospis and A. bambawalei recorded more than 70% mortality. Thiodicarb was extremely toxic to P. solenopsis and least toxic to A. bambawalei where as Spinosad was less toxic to P. solenopsis and extremely toxic to A. bambawalei. Profenophos, Thiamethoxam and Chlorpyriphos results into > 90% mortality of P. solenospsis while 100% kill of A. bambawalei with Spinosad, Acephate and Chlorpyriphos up to 48 hours. More than 80% mortality of P. solenopsis with Chlorpyriphos, Profenophos, Monocrotophos, Thiamethoxam, Spinosad and of A. bambawalei with Profenophos, Monocrotophos, Flonicamid, Buprofezin, Imidacloprid, Thiamethoxam, Chlorantraniliprole, Flonicamid and Indoxacarb recorded 72 hours after exposure. While at 96 hours, cent per cent mortality of P. solenopsis was recorded with Monocrotophos which was equivalent to Acephate and Spinosad. Least LT50 values were found with Thiodicarb, Quinalphos and Thiamethoxam for P. solenopsis and higher in case of Thiodicarb for A. bambawalei. Spinosad, Chlorpyriphos and Quinalphos were found to be extremely toxic to A. bambawalei. Among the tested insecticides Thiodicarb was found effective against P. solenopsis and relatively safer to A. bambawalei may be used judiciously to manage P. solenopsis that have least implications on the environment.