Dissipation pattern of azoxystrobin and difenoconazole in red dragon fruit (Hylocereus polyrhizus) cultivated in Indonesian highland (West Java) and coastal area (D.I. Jogyakarta) and its implication for dietary risk assessment

Abstract

Cultivation of red dragon fruit (Hylocereus polyrhizus) in Indonesian orchards is hampered by anthracnose and stem canker. A mixture of azoxystrobin 200 g/L + difenoconazole 125 g/L is recommended in supporting the obligated integrated pest management. For the consumer safety, dietary intake of the residues from fresh edible part should be assessed; therefore, information on correct dissipation pattern of the applied pesticide is required. Field residue trials in Indonesian highland (West Java) and coastal area (Special Region of Yogyakarta) were done at recommended dose was 0.151 kg ai/ha azoxystrobin and 0.094 kg ai/ha difenoconazole, three times at 10 days interval. Whole fruit samples were collected at 70%–100% ripeness at −1, 0, 1, 3, 7, 10, and 14 days after last application, processed and determined its residue as soon as possible. Photoisomerization of azoxystrobin was observed at Day 0, especially in coastal area; however, it has been dissipated to below lowest validated level in the following day. At Day 0, 3%–5% of the deposited azoxystrobin and difenoconazole penetrate into the flesh; however, most residues (95%–97%) were retained in peel, and dissipated in prolonged day. The dissipation pattern was non-linear. The dissipation data were better fit with bi-exponential double-first-order in parallel than single first-order kinetics model. The DT50 of both azoxystrobin and difenoconazole was 3 days. At harvest time, seventh day, only azoxystrobin residue was detected in flesh at 0.006 mg/kg; therefore, the long-term dietary risk was 0 per cent acceptable daily intake. Fresh red dragon fruit is safe to consume.