Residue Behavior of Clopyralid Herbicide in Soil and Sugar Beet Crop under Subtropical Field Conditions

Sugar beet is a major crop for the sugar industry. With growing awareness of unsystematic use of pesticides, health problem, and environmental issues, assessment of pesticide residues in soil and crops has become necessary. Studies of subtropical conditions on dissipation and residue analysis of clopyralid have not yet been reported. Therefore, dissipation kinetics and terminal residues of clopyralid for two cropping seasons in the soil and the sugar beet crop were studied under field conditions. An experiment was laid out in a randomized block design, and a herbicide was applied as a postemergent. Clopyralid was extracted from the matrix by basic water, subjected to solid phase extraction cleanup, and quantified by high-pressure liquid chromatography-UV. The method was validated, and recovery percentage of pesticide ranged from 81 to 88, 77 to 85, 78 to 86, and 89 to 94% in the soil, sugar beet roots, sugar beet leaves, and water, respectively. After application in the soil, clopyralid dissipated rapidly following monophasic first-order kinetics, with a half-life of 13.39 days. Limits of detection and quantitation were 0.007 and 0.02 μg g-1, respectively. Clopyralid does not persist long in soil, and residues were below the European Union's maximum residue levels (0.5 mg kg-1) in the roots and leaves of sugar beet. Residues were also not detected in the groundwater. It can be concluded that clopyralid could be considered a safe herbicide from the environmental aspect due to its nonpersistence and that it would not have an adverse effect on human or animal health.