‘Honeycrisp’ is a popular cultivar that is currently being planted in large numbers in northern regions of the United States and Canada. ‘Honeycrisp’ is highly susceptible to soft scald, a chilling disorder characterized by sharply defined browning of the skin and underlying tissue. To prevent this disorder, special postharvest treatment such as delayed cooling and/or storage temperatures are necessary to minimize losses. Methods used to prevent soft scald are not always effective and can lead to other disorders and quality loss (Watkins et al., 2005), which could limit production of this cultivar.
In susceptible cultivars, soft scald develops within a few weeks to months on placement in cold storage and is more severe at temperatures below 3 °C (Brooks and Harley, 1934). Storing fruit at temperatures above 2.5 °C reduces the incidence and is recommended for prevention (Magness and Burroughs, 1923; Meheriuk et al., 1994) but is not consistently effective in ‘Honeycrisp’ (DeLong et al., 2004; Watkins et al., 2005). In addition, storage temperature above 3 °C can lead to quality loss and may also necessitate separate storage facilities when other cultivars require colder storage temperatures (Watkins et al., 2005).
Susceptibility to soft scald increases with later harvest dates (Tong et al., 2003; Watkins et al., 2004). As a result, harvest at earlier stages of maturity, when starch index is below 6.0, is recommended for prevention (Greene and Weis, 2001). However, harvesting at an earlier stage of maturity is not always effective in preventing soft scald (DeLong et al., 2004; Watkins et al., 2005). In addition, when fruit are harvested early to prevent soft scald, flavor may not be sufficiently developed for high consumer appeal (Wargo and Watkins, 2004).
Soft scald varies considerably in its occurrence from year to year and appears to vary in severity between different growing regions in ‘Honeycrisp’ (Watkins et al., 2004) and ‘Jonathan’ apples (Plagge and Maney, 1937). Severity can range from most or all of the fruit being afflicted to few or none in other instances (DeLong et al., 2004; Wargo and Watkins, 2004). The cause of this variability remains unknown. Environmental variables such as temperature and orchard management such as nutrition have been implicated in predisposing fruit to disorders (Autio et al., 1986; Ferguson et al., 1999; Smock, 1977), but the role of these factors in the development of soft scald has not been established. Elucidating environmental and orchard factors could allow growers to predict soft scald occurrence and to subsequently make harvest and storage decisions that minimize losses. The objective of this study was to evaluate the influence of preharvest environmental variation in temperature and precipitation on the occurrence of soft scald in ‘Honeycrisp’ apples.
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