Decomposition of myclobutanil and triadimefon in grapes on the vines and during refrigerated storage

Decompositions of the triazole fungicides, myclobutanil and triadimefon, in table grapes, of a Greek variety, on the vines and during refrigerated storage, were studied. Vines of the Greek variety, Opsimo Edessas, were separately sprayed onto the vines with trade preparations of myclobutanil and triadimefon. Samples were collected from the vines after 1, 5, 11, 25, 35 and 46 days. Also, a representative 15-kg sample of grapes, for each fungicide, was collected 2 h after the pesticide applications and stored in a refrigerator at 0 °C. Samples from the refrigerator were removed every 10–30 days for 7.5 months. Residues were determined by a simple gas-chromatographic method. The recovery of myclobutanil was found to be from 88 up to 106% and, of triadimefon, from 94 up to 105%. The limit of determination was 0.02 mg/kg for myclobutanil and 0.04 mg/kg for triadimefon. Half-lives for myclobutanil and triadimefon were 10.5 and 16.5 days respectively, for decomposition on the vines and 92.4 and 216 days, respectively, for decomposition during storage in a refrigerator.