Under certain conditions the compound becomes toxic to the cells of the skin. Scald, evident only after several months of storage, first appears on skin on the green side of fruit as an irregular burned or scalded area. Fruit removed from storage after December may not show symptoms at first, but when allowed to stand at room temperature for 12 to 24 hours may begin to exhibit scald. The flesh immediately below the affected area may become soft and discolored if scald is severe. If this happens, the fruit cannot be peeled easily when processed.
Scald severity is influenced by variety, season, cultural practices, and postharvest treatments.
Susceptible varieties include Stayman, Winesap, Ben Davis, Cortland, Fuji, Rome Beauty, Rhode Island Greening, York Imperial, and Granny Smith. Less susceptible are Jonathan, Delicious, Spartan, McIntosh, Northern Spy, and Golden Delicious. Warm temperatures during the last 6 weeks before harvest may increase the likelihood of scald. Hot, dry weather increases susceptibility, while cool, damp weather decreases it. Studies in New Jersey with Stayman showed that when fruit experienced 190 hours or more of temperatures below 50 F on the tree, scald did not develop.