Using Pyraclostrobin Fungicide for Development of Fruit Skin Color Quality of Longan

Abstract

This study evaluated the impact of the fungicide Pyraclostrobin on fruit skin color quality in the "Dow" variety of longan (Dimocarpus longan), using 20-year-old trees in a farmer's orchard in Muang district, Lamphun. Pyraclostrobin was sprayed at a concentration of 10 mL per 20 liters of water when the fruit reached a diameter of 1.5-2.0 cm (60 days before harvesting). The experimental design was Completely Randomized Design (CRD) with four treatments as 1) untreated (control), 2) one application 30 days before harvesting, 3) two applications at 30 and 45 days before harvesting, and 4) three applications at 30, 45, and 60 days before harvesting. Results indicated that two and three applications of Pyraclostrobin significantly increased fruit brightness (L) compared to the control, though there were no significant differences in the red (a) and yellow (b) values among the treatments. Chemical residue analysis revealed treated fruits contained very low levels (0.02-0.05 mg/kg) within acceptable MRL standards while no Pyraclostrobin was found in the control fruits.  The disease index at harvest showed 21.9, 13.7 and 13.5% in the one-application, two-application, and three- application treatments, respectively, significantly lower than the control (37.6%). The study demonstrates that one to three-applications of Pyraclostrobin before harvest can improve fruit brightness and reduce disease index without exceeding MRL standards.