Triazole fungicide degradation in peaches in the field and in model systems.

The degradation of five triazole fungicides (cyproconazole, hexaconazole, penconazole, propiconazole, tebuconazole) in peaches was evaluated in field studies to establish whether at the preharvest interval the residue levels were below the legal limit established in Italy. All fungicides, except propiconazole, showed higher residues than the legal limits because of their high stability. In fact, some did not decrease at all (cyproconazole, penconazole, tebuconazole), while others decreased only in part. The increasing weight of the fruit during growth was the main factor leading to an apparent decrease in pesticide levels on a weight for weight basis. The trials on model systems showed that co-distillation and sunlight photodegradation were the main mechanisms leading to a decrease in triazole levels. Although these fungicides are systemic, they did not enter the fruit and all residues were only present in the peel.