Washington State University--Tree Fruit Research & Extension Center

Postharvest Physiology

Scald prediction model: central Washington orchards

The appearance of storage scald is related to orchard temperatures during the final weeks of fruit ripening. Scientists working on systems to predict its occurence have determined that fruit susceptibility decreases as the number of hours below 50ƒF increases. Tabulated below are two ways to compute the number of hours below 50ƒF. "SCH" adds together the number of degree hours below 50ƒF. "Hours" simply adds the number of hours below 50ƒF. Dr. Eric Curry, USDA ( curry@tfrl.ars.usda.gov ) , has shown that with starch less than 3.0, after 150 hours (not SCH) scald symptoms are slight. If the starch is greater than 3, then maturity will take over and decrease scald susceptibility.

Data tabulation began on August 16 for both systems. Contact Gene Kupferman (kupfer@wsu.edu) or Dana Faubion (faubiond@wsu.edu) for further information.

SCH=Scald Control Hours below 50 since 08/15/97
Hours=number of hours below 50 since 08/15/97

This data would not be available without the Washington Public Agriculture Weather System (PAWS). Please give them your support!

WSU-TFREC postharvest page

Washington State University
Tree Fruit Research and Extension Center
1100 N. Western Ave.
Wenatchee WA 98801

phone: 509-663-8181
fax: 509-662-8714

Wenatchee WA
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Scald photo credit to Joe Ogawa & Harley English