Dissipation of imidacloprid residues in mango orchard soil quantified by HPLC

Imidacloprid, a neonicotinoid insecticide, is widely used in mango ecosystem to control mango hopper at prebloom stage. Persistence of imidacloprid in soil is well reported. While spraying any insecticide to a tree, some portion does come in contact with rhizosphere soil. Hence after spraying at 0.005 per cent to mango (cv. Dashehari) trees, its residue was analyzed in rhizosphere soil by HPLC. Soil samples were extracted with acetonitrile by vortexing followed by ultrasonic solvent extraction without any cleanup. Imidacloprid dissipated from its initial deposit of 0.760 mg g⁻¹ at zero day to 0.044 mg g⁻¹ after 60 days of spraying in mango orchard soil (Sandy loam). After 60 days of application, 94.21 per cent of imidacloprid degradation was recorded in soil. The dissipation rate followed pseudo first-order kinetics in soil with calculated half-life (DT₅₀) value of 17.5 days. Imidacloprid has been found a persistent insecticide in mango orchard soil.