Field dissipation, dietary risk assessment, and soil fate of chlorantraniliprole and abamectin (dual-active formulation) in watermelon under field conditions

Chlorantraniliprole and abamectin are frequently applied in combination for pest management in cucurbit crops; however, field-based residue data for their joint use on watermelon remain limited. The present study evaluated the dissipation behaviour, soil residues, and dietary exposure implications of a dual-active formulation (chlorantraniliprole 4.3% + abamectin 1.7% SC) applied to watermelon under supervised field conditions. Fruit samples were collected at 0, 1, 3, 5, 7, 10, and 15 days after the final application, and soil samples were collected at harvest. Residue analysis was performed using LC-MS/MS following modified QuEChERS extraction with matrix-matched calibration. The analytical method demonstrated satisfactory performance, with linearity (R2 ≥ 0.995), mean recoveries within 95–109%, and relative standard deviations below 8%, consistent with internationally accepted validation criteria. At the recommended dose, initial fruit residues were 0.081 mg/kg for chlorantraniliprole and 0.125 mg/kg for abamectin (expressed as avermectin B1a equivalents). Residues declined following first-order kinetics, with calculated half-lives of 4.72–5.11 days for chlorantraniliprole and 6.72–7.55 days for abamectin. Both compounds decreased to below their respective limits of quantification (0.03 mg/kg for chlorantraniliprole and 0.01 mg/kg for abamectin) within 7–10 days. No quantifiable residues were detected in soil at harvest. Screening-level dietary risk assessment using conservative Day 0 residue values indicated negligible chronic exposure for chlorantraniliprole (HQ = 0.000041 for adults) and acceptable exposure for abamectin (HQ = 0.125 for adults; 0.375–0.50 for children). Acute exposure assessment for abamectin corresponded to 12.5% of the ARfD. These findings indicate that, under recommended application practices and with adherence to a 10-day pre-harvest interval, consumer exposure remains within acceptable toxicological limits. This study provides integrated residue dissipation and exposure data for chlorantraniliprole-abamectin use in watermelon and contributes evidence relevant to regulatory evaluation and development of crop-specific residue guidelines.