Residues of difenoconazole and penconazole on apple leaves and grass and soil in an apple orchard in north-eastern Switzerland

The two DMI fungicides difenoconazole (Score 10 WP), and penconazole + captan (Topas C), were applied four times in 1992 and in 1993 in an apple orchard in north-eastern Switzerland. Residues of difenoconazole and penconazole were monitored by sampling leaves, grass and soil. Highest values were found immediately after a series of four fungicide sprays. Residues of penconazole were lower in most instances than those of difenoconazole. From the beginning of the study in October 1991, till the end of the study in October 1993, there was no accumulation of either difenoconazole or penconazole in the soil.