Comparative effectiveness of chemical biocides and Acalypha wilkesiana leaf extract against postharvest fungal deteriogens of sweet orange (Citrus sinensis) fruits

This study determined the in-vitro and in-vivo activities of Voriconazole (VOR, 1 µg), Nystatin (NYS, 25 µg), Fluconazole (FLC, 100 µg), red force® (RFC) [Copper (I) oxide, 60% + Metalaxyl-M 6% WP], ultimax plus® (UPL) [Metalaxyl 12% WP + Copper (I) oxide 60% WP], and forcelet® (FCE) [Carbendazim 50% WP] and Acalypha wilkesiana (Red Acalypha) on fungal deteriogens obtained from deteriorated sweet orange fruits. The 22 fungal deteriogens tested had in-vitro susceptibility of 13.0 ± 2.6-28.7 ± 1.2 mm inhibition zone for VOR (n = 14), 9.3 ± 1.2-28.0 ± 3.0 mm for NYS (n = 21), 7.7 ± 1.5-21.7 ± 1.5 mm for FLC (n = 4), 13.3 ± 1.2-31.7 ± 2.1 mm for RFC (n = 5), 15.3 ± 4.2-30.7 ± 1.2 mm for UPL (n = 5), 15.7 ± 1.2-31.7 ± 1.5 mm for FCE (n = 19) and 0.0 ± 0.0 mm for Red Acalypha (n = 22). Fifteen of the fungal deteriogens including the yeast, Candida glabrata were able to initiate deterioration in-vivo with 40-100% severity within the incubation period of 11 days. FCE biocide significantly (p = 0.001) prevented or reduced deterioration in-vivo. There was no deterioration sign in uninoculated control (Control 1) and uninoculated control with FCE (Control 2). Further search for active agents against fungal deteriogens especially from natural sources is required for longer preservation of Citrus sinensis.