Control of rhizopus rot of peaches with postharvest

Rhizopus rot caused by Rhizopus stolonifer is a potentially serious postharvest 1 disease of Canadian-grown peaches. Several new fungicides are effective against brown rot 2 (Monilinia fructicola) of peaches, but little is known of their postharvest efficacies against R. 3 stolonifer. Harvested peaches were arranged in trays, individually punctured once and 4 co-treated with a suspension of both R. stolonifer sporangiospores and cells of an isolate of 5 Pseudomonas syringae or one of 13 fungicides at 0.5-1.0 times the dilute concentration used to 6 control brown rot in orchard programs. In subsequent experiments, the peaches were 7 inoculated with R. stolonifer, incubated for 6 h, chilled, and a day later the inoculated sites were 8 brushed with a suspension of fludioxonil, tebuconazole or P. syringae. In the co-treatment 9 studies, azoxystrobin, fenhexamid, fenbuconazole, myclobutanil, benomyl and sulfur reduced 10 rhizopus rot by 0-22%. Cyprodinil and propiconazole gave 20-60% reduction, while 11 fludioxonil, tebuconazole and two P. syringae isolates gave 75-100% reduction, comparable to 12 that of dicloran and iprodione. Post-inoculation brushing treatments with P. syringae at 13 10,000μg ESC 10/mL gave less than 20% control while fludioxonil and tebuconazole gave 90% 14 control (EC90) at 472 μg/mL and 718 μg/mL, respectively. 15 16 17