Field Dissipation, Dietary Risk Assessment, and Soil Fate of Chlorantraniliprole and Abamectin (Dual-Active Formulation) in Watermelon under Field Conditions

Chlorantraniliprole and abamectin are widely applied together for pest management in cucurbit crops; however, comprehensive field residue data for their combined use on watermelon remain absent. This study characterizes the dissipation dynamics, dietary safety profile, and environmental fate of chlorantraniliprole and abamectin following application of a dual-active formulation (Voliam Targo; 4.3% + 1.7% SC) to watermelon under supervised field conditions. Fruit samples were collected at 0, 1, 3, 5, 7, 10, and 15 days after final spray; soil samples were collected at harvest. Residues were analyzed by LC-MS/MS following a modified QuEChERS extraction with matrix-matched calibration. The method demonstrated excellent analytical performance: linearity R² > 0.995, recovery 94.8-107.8%, and precision (RSD) < 8%. At the recommended dose, initial residues were 0.081 mg/kg (chlorantraniliprole) and 0.125 mg/kg (avermectin B1a); both declined below their respective limits of quantification (0.03 and 0.05 mg/kg) within 7–10 days following first-order exponential decay kinetics (half-lives: 3.79–4.1 days for chlorantraniliprole; 6.7–7.5 days for abamectin). Soil analysis at harvest revealed no detectable residues, indicating minimal environmental transfer. Dietary risk assessment showed chlorantraniliprole posed a negligible risk (hazard quotient = 0.002), while abamectin residues were safe when realistic pre-harvest intervals were applied (HQ declined from 2.08 at day 0 to 0.52 at day 7). These integrated findings, combining rapid dissipation, soil safety, and dietary risk characterization, establish a scientific basis for a 7-10day pre-harvest interval and support in establishing crop-specific maximum residue limits and pre-harvest intervals for watermelon.