Aphidicidal Activity of Some Systemic Insecticides and Change in Susceptibility Level of Myzus persicae Sulzer in Vegetable Ecosystem in Varanasi, India

In-vitro toxicity of some organophosphorus and newer synthetic insecticides against green peach aphid, Myzus persicae Sulz., black bean aphid, Aphis craccivora Koch. and mustard aphid, Lipaphis erysimi (Kalt.) is reported by the direct spray method. Amongst newer molecules, acetamiprid 20 per cent SP was the most toxic against all the three vegetable aphid species with median lethal concentrations (LC₅₀) of 0.086, 0.545 and 1.84 ppm against A.craccivora, M. persicae and L. erysimi, respectively. Differential responses of aphids towards the test insecticides were observed. A. craccivora was the most susceptible one followed by M. persicae and L. erysimi. A comparison of LC₅₀values for the commonly used and recommended insecticides determined over eight years revealed a shift in susceptibility to imidacloprid, thiamethoxam and dimethoate where M. persicae showed 5.90, 2.51 and 2.72 fold resistance to these insecticides, respectively.