MARKET DISEASES OF FRUITS AND VEGETABLES 51 



45-second exposure to a temperature of 110° F. is about as much 

 as apples of most varieties will stand without cracking. The York 

 Imperial seems to be especially subject to this injury and 

 should be handled accordingly, either by reducing the tempera- 

 ture of the washing solution or by shortening the exposure. It is 

 generally not necessary to use heated solutions, unless unusual 

 spray practices have been followed. 



Heat cracking is characterized by numerous fine cracks run- 

 ning latitudinally around the apple, especially in the region around 

 the calyx, and often extending out onto the cheek. The cracks 

 develop within 24 hours after the washing treatment as fine white 

 lines that are clearly visible. As the tissues begin to dry out the 

 cracks widen until they assume the general appearance of ad- 

 vanced stages of York skin crack. However, in heat cracking the 

 regularity of form and location is more pronounced than in the 

 other type. Like apples affected with other forms of skin cracking 

 that expose the underlying flesh, heat-cracked apples are subject 

 to early wilting and decay. Apples are somewhat more susceptible 

 to this type of injury at the time of harvest than after being 

 kept for several weeks. 



(See U, U6, 121, 130.) 



HYDROCHLORIC ACID INJURY AND SKIN CRACKING 



(See Injury by Hydrochloric Acid, p. 24.) 



Soft Scald 



Soft scald is a nonparasitic disease of apple that is sporadic 

 in its occurrence even on highly susceptible varieties, but it 

 sometimes causes heavy losses. It occurs most frequently on Jon- 

 athan, Mcintosh, Rome Beauty, and Wealthy, but it is occasionally 

 found on Stayman, Winesap, Winter Banana, Baldwin, Wagener, 

 Grimes Golden, Northern Spy, and other varieties. 



The disease is characterized by peculiar patches and ribbonlike 

 areas of brown tissue on the surface of the apple and by a sharp 

 line of demarcation between the diseased and the healthy tissue 

 (pi. 8, G, H). Sometimes only the skin of the apple is affected, 

 but more often the browning extends into the flesh for % inch or 

 more. Black spots on areas injured by soft scald are usually caused 

 by secondary infection by Cladosporium or Alternaria. 



Soft scald is apparently due to abnormal respiratory condi- 

 tions in the apple. It is much more likely to develop at tempera- 

 tures that border on the freezing point of apples than at those 

 a few degrees higher and is greatly increased by delay in placing 

 the fruit in storage. 



Oiled paper does not control soft scald. Holding the apples in 

 an atmosphere containing 20 to 30 percent of carbon dioxide for 

 2 days during the period of cooling has largely or entirely pre- 

 vented the later development of soft scald, but this treatment 

 has not become an established practice. 



(See 12, 16, 50, 59, 105, 106, 111*.) 



Soggy Break-Down 



Soggy break-down is a nonparasitic disease of apple that some- 

 times has been included under internal break-down, but it appears 



