Double exponential decay modeling for estimating permissible pre-harvest residue levels of pesticides in apples (Malus pumila)

Simulating the residual magnitudes of pesticides applied to crops during cultivation is essential for determining appropriate harvest timing to guarantee safe agricultural products. In this study, field experiments were performed to evaluate the time-dependent persistence of pesticides captan (CT), lufenuron (LF), tebufenozide (TB), and teflubenzuron (TF) applied to apples at recommended and three-fold higher doses. Subsequently, various kinetic models were applied to the residual data for calculating pre-harvest residue limits (PHRLs) which indicate permissible pesticide concentrations during the pre-harvest period. The double-exponential model best fitted persistence trends of all tested pesticides in apples (R² = 0.67 - 1.00), outperforming zero-, first-, and second-order models. TB, vulnerable to sunlight, exhibited shortest half-lives in apples (0.2 - 0.4 days). Systemic insecticide TF showed longest half-lives in apples (24.6 - 29.3 days), while CT and LF ranged 8.6 - 9.9 and 11.3 - 16.1 days, respectively. Double-exponential parameters enabled PHRL estimation for determining safe apple harvest dates ensuring pesticide concentrations below maximum residue limits. This model provides accurate PHRL calculations, helping farmers produce safer apples from pesticide residues.