Multiple factors affecting occurrence of soft scald and fungal decay in apple during storage

Some apple cultivars are highly susceptible to soft scald, a physiological disorder that can lead to large losses. The effect of harvest time, gradual cooling regimes and storage conditions on soft scald and fungal decay was investigated in two common apple cultivars, 'Aroma' and 'Frida' in a three year trial 2018-2020. Further, possible relationships between weather conditions during the growing season and 28 d before harvest and soft scald incidence along with fungal decay after storage were studied. The year with the highest rainfall had the highest incidence of soft scald and fungal decay. Our results suggest that the relative humidity during a period of 28 d before harvest was important for later development of soft scald in 'Frida', and together the results from 'Frida' and 'Aroma' showed a moderate correlation between relative humidity and soft scald. Gradual cooling showed conflicting results, and no treatment consistently lowered soft scald incidence. Gradual cooling led to inconclusive results, and storage in ambient air led to higher incidence of soft scald as compared to some investigated ULO storage conditions. Advanced maturity was associated with soft scald development and more fungal decay in one out of three years in 'Aroma', but did not affect incidence in 'Frida'. The etiology of soft scald seems to be dependent of multiple factors.

Automated summary

The effects of harvest time, gradual cooling regimes, and storage conditions on soft scald and fungal decay in two apple cultivars were studied. Results showed that the year with the highest rainfall had the highest incidence of soft scald and fungal decay. Relative humidity during the 28 days before harvest was found to be important for the development of soft scald. However, there were conflicting results for gradual cooling and no treatment consistently lowered soft scald incidence. Advanced maturity was associated with soft scald development and more fungal decay in one out of three years. The etiology of soft scald seems to be dependent on multiple factors.