Application of Alternatives to Synthetic Fungicides to Control Postharvest Disease of Sweet Cherry

Prunus avium; Monilinia spp.; Botrytis cinerea, antimicrobials, resistance inducers, chitosan, poscosecha, postcosecha, postharvest Sweet cherry (Prunus avium) is a perishable fruit, and during storage it can undergo postharvest decay. This is mainly caused by Monilinia spp. and Botrytis cinerea, and occasionally by Rhizopus stolonifer, Alternaria alternata, Penicillium expansum, and Cladosporium spp. At present, preharvest treatments with synthetic fungicide are the main means for postharvest disease control in stone fruit. However, alternatives to the use of synthetic fungicides are needed for the sweet cherry market, where no fungicides are licensed for postharvest application and none allowed in organic agriculture. Natural compounds with antimicrobial activity and eliciting properties might represent alternatives to synthetic fungicides in the control of postharvest disease of fruit. The aim of the present study was to test the effectiveness of these alternatives to control pathogens causing postharvest diseases of sweet cherry in vitro and in vivo. Oligosaccharides, benzothiadiazole, chitosan, calcium plus organic acids, or nettle extract, when amended with PDA, Potato Dextroxe Agar, reduced the growth of Monilinia laxa, B. cinerea and R. stolonifer. Treatments of sweet cherries 3 days before harvest or soon after harvest with oligosaccharides, benzothiadiazole, chitosan, calcium plus organic acids, nettle extract, fir extract, laminarin, or potassium bicarbonate reduced postharvest brown rot, gray mold, Rhizopus rot, Alternaria rot, blue mold and green rot of sweet cherries stored at 1?1?C and/or at 20?1?C. Among these resistance inducers, when applied either preharvest or postharvest, chitosan was one of the most effective in reducing postharvest decay of sweet cherry, and its antimicrobial action was comparable to the one of the fungicide fenhexamid. Benzothiadiazole was more effective when applied postharvest than when sprayed in the field. Phytotoxic effects were only seen after potassium bicarbonate applications at concentrations >1%. Information about the authors and sources:Romanazzi, G., Feliziani, E.Department of Agricultural, Food and Environmental Sciences, Marche PolytechnicUniversity, Via Brecce Bianche, 60131 Ancona, Italy; g.romanazzi@univpm.it International Symposium on Plum and Sweet Cherry, 24 & 25th October? 2012. Organized by the research group "Post-Recolecci?n de Frutas y Hortalizas" Universidad Miguel Hern?ndez, de Elche, UHM, Spain The picture shows boxes with cherries, to be sent by the Chilean company Frusan to Far East Asian markets.