Pre- and postharvest treatment with alternatives to synthetic fungicides to control postharvest decay of sweet cherry

The effectiveness of alternatives to synthetic fungicides for the control of pathogens causing postharvest diseases of sweet cherry was tested in vitro and in vivo. When amended to potato dextrose-agar, oligosaccharides, benzothiadiazole, chitosan, calcium plus organic acids, and nettle macerate reduced the growth of Monilinia laxa, Botrytis cinerea and Rhizopus stolonifer. Treatment of sweet cherries three days before harvest or soon after harvest with oligosaccharides, benzothiadiazole, chitosan, calcium plus organic acids, nettle extract, fir extract, laminarin, or potassium bicarbonate reduced brown rot, gray mold, Rhizopus rot, Alternaria rot, blue mold and green rot of cherries kept 10 d at 20 ± 1 °C, or 14 d at 0.5 ± 1 °C and then exposed to 7 d of shelf-life at 20 ± 1 °C. Among these resistance inducers, when applied either preharvest or postharvest, chitosan was one of the most effective in reducing storage decay of sweet cherry, and its antimicrobial activity in vitro and in field trials was comparable to that of the fungicide fenhexamid. Benzothiadiazole was more effective when applied postharvest than with preharvest spraying. These resistance inducers could represent good options for organic growers and food companies, or they can complement the use of synthetic fungicides in an integrated disease management strategy.

► Resistance inducers reduced the radial growth of decay causing fungi.
► Treatment with resistance inducers reduced postharvest decay of sweet cherry.
► Among resistance inducers, the most effective in decay control was chitosan.
► Benzothiadiazole was more effective applied after harvest than before harvest.
► The effectiveness of chitosan was comparable with the fungicide fenhexamid.