Effectiveness of imidacloprid and thiamethoxam in controlling wheat aphids and the dynamics of pesticide residues in wheat leaves

The relative effectiveness of two second generation neonicotinoid insecticides,thiamethoxam and imidacloprid,in controlling wheat aphids and the dynamics of their residues in wheat leaves was investigated.Wheat seeds were treated with 0.5,1,2 and 4 a.i.g/kg of either thiamethoxam or imidacloprid before sowing and the population density of wheat aphids and the amount of pesticide residue in wheat leaves was determined at different points in time.The results show that both pesticides were effective in reducing populations of wheat aphids and the damage these cause to wheat crops.The best results were achieved by spraying wheat seeds with 2 and 4 a.i.g/kg of 25% imidacloprid and 1,2 and 4 a.i.g/kg of 70% thiamethoxam.The concentration of thiamethoxam in wheat leaves before 10-Apr.was significantly lower than that of imidacloprid,but there was no difference in the amount of residue of either pesticide after 28-Apr.In conclusion,thiamethoxam is a better choice for controlling wheat aphids than imidacloprid.