44 MISC. PUBLICATIOISr 16 8, U.S. DEPT. OF AGRICULTUEE 



Apples usually show but little scald while held continuously in cold 

 storage, but fruit that is apparently free from the disease at 32° F. 

 often becomes badly scalded after a few days' exposure to warm air. 

 However, the higher temperature does not really cause the scald; it 

 merely brings out what was already latent in the fruit. 



Scald is worse on immature than on mature fruit, and worse on 

 apples from heavily irrigated trees than on those from trees receiving 

 more moderate irrigation. It develops more rapidly at high than at 

 low temperatures and is worse in standard commercial barrels than 

 in more open packages, such as the box, basket, or ventilated barrel. 

 Open stacks and air spaces that provide air circulation in the storage 

 room contribute to the prevention of scald, but cannot be relied upon 

 for the control of the disease. 



Delayed storage may greatly increase the later development of 

 scald, especially if the fruit receives little ventilation during the 

 delay, although with immature fruit a delay with free exposure to 

 the open air sometimes reduces the later development of scald. 



CAUSAL FACTORS 



The real cause of scald is. the accumulation within the apple tissues 

 of certain gases that are produced by the apples themselves as a 

 result of their continued respiratory activity. These gases can be 

 removed by aeration and ventilation, but this is difficult to accomplish 

 in closed packages under the usual storage conditions. However, the 

 injurious gases can be absorbed by oils, which give the basis for a 

 most efficient and practical method of scald control, that of packing 

 the apples in oiled (not waxed) paper. 



CONTROL MEASURES 



Oiled wraps should be used on boxed apples and shredded oiled 

 paper should be scattered among apples in barrels, hampers, and 

 baskets. About one half pound of shredded paper is required for 

 each bushel of apples, and it must be well distributed in the package, 

 practically every apple having more or less contact with the paper. 

 The oiled wraps should carry at least one fourth of a gram of oil per 

 sheet, and both wraps and shredded oiled paper about 15 percent 

 of their finished weight in odorless, tasteless mineral oil, although 

 18 or more percent of oil is desirable, especially if lightweight paper 

 is to be used on the more susceptible varieties of apples. The apples 

 should be packed in the oiled paper as soon as possible after picking. 

 Unless this is done within 3 or 4 weeks it is not usuallv possible 

 to overcome the tendency to scald. {11, 13, 19, 20, 21, 22, \3, 2^, 28, 

 60, 62, 80 86, 100, UO, IJfS, lU. 179, 180, 182, 186, 195, 236.) 



SOFT SCALD 



Soft scald is a nonparasitic disease of apples that is sporadic in 

 its occurrence even on susceptible varieties, yet sometimes causes 

 heavy losses. It occurs most frequently on Jonathan and Rome 

 Beauty but is occasionally found on Stayman Winesap, Winesap, 

 Winter Banana, Baldwin, Wagener, Grimes Golden, Northern Spy, 

 and other varieties. 



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