Dissipation of Triazole Fungicides in Apples

Triazole compounds are members of the demethylation inhibitor class of systemic agents used to combat the most widespread apple diseases worldwide, namely apple scab and powdery mildew. The dissipation kinetics of difenoconazole, mefentrifluconazole, myclobutanil, penconazole, tebuconazole and tetraconazole from commercial products in two apple cultivars (Rosana and Selena) were studied over four years. Pesticide residues in the apples were determined using the QuEChERS extraction procedure, followed by liquid chromatography-mass spectrometry analysis. Triazoles applied 84-100 days before harvest dissipated faster than those applied 44-55 days before harvest, with half-lives of 4.0-22.3 days and 7.1-43.9 days, respectively. Except for tebuconazole, all triazoles were found to be well below 30% of the maximum residue levels at the end of the pre-harvest interval, which is mandatory for products in use. The dissipation of five triazoles was evaluated during cold storage over two subsequent years. Residues of difenoconazole, myclobutanil and tebuconazole were detected at levels above 0.01 mg/kg after more than five months. The calculated risk intake values were lower than the established acceptable daily intake and acute reference dose values, indicating that the acute and chronic risks of pesticide exposure from consuming apples are not expected.