Understanding infection risk factors for integrated disease management of brown rot and grey mould in sweet cherry

Brown rot and grey mould cause significant losses in sweet cherry due to rot of fruit at harvest, particularly in wet years. Studies in a Tasmanian orchard found that Botrytis cinerea was associated with 95% of fruit which was symptomatic at harvest, while Monilinia spp. were not detected. Total rot at harvest varied significantly with cherry cultivar. To determine how disease develops during the season, samples of fruit from two cultivars ('Simone' and 'Regina') were obtained fortnightly over a 53 day period prior to commercial harvest and expression of “latent” non-symptomatic infections was induced. While incidence increased towards harvest, this study showed that a substantial amount of infection had already occurred prior to 53 days before harvest. To quantify how fruit susceptibility to infection changes over time, a controlled incubation experiment was conducted which showed that infection risk increases with time and the odds of infection was quantified for three different cultivars and three pathogens. This information will form a basis for development of grower tools to guide decision-making about infection risk.