MARKET DISEASES OF APPLES, PEARS, QUIISrCES 49 



During storage, sunburned areas often develop an appearance that 

 is difficult to distinguish from scald (pi. 9, E). In other respects the 

 keeping quality of sunburned apples is not materially affected. 



The true sun scald is found occasionally as small white or tan- 

 colored, slightly shriveled spots, especially on apples formerly pro- 

 tected but suddenly exposed to the sun. In severe cases, as when 

 an apple lying on the ground has been truly scalded, the skin and 

 flesh present the appearance of having been half-baked in an oven. 



WATER CORE 



Water core occurs in practically all apple sections of the United 

 States, but is of greatest importance in those regions having an arid 

 or semiarid climate. Among the most susceptible varieties are Yel- 

 low Transparent, Rambo, Pmnpkin Sweet, Tompkins King, Fall 

 Pippin, Early Harvest, Jonathan, Delicious, Staj^man Winesap, 

 Winter Banana, Arkansas (Mammoth Black Twig), and Winesap. 

 The latter variety .in the Northwest is more often affected than any 

 other. 



Water core is a nonparasitic disease characterized by hard, glassy, 

 water-soaked regions in the flesh of the apple. The disease is more 

 commonly found in the region of the core and of the primary 

 vascular bundles, but may occur in any part of the apple or may 

 involve the whole of it (pi. 8, A). When only the core area is 

 involved it is impossible to detect the disease without cutting the 

 fruit. Visible water core is frequently associated with sunburn. 



Water core is particularly bad in regions of intense heat and sun- 

 light. High temperature at the time the apples are approaching 

 maturity is especially favorable to its development. The disease is 

 most likely to occur in fruit that is freely exposed to the sun. It 

 often increases rapidly as the apples become overmature. 



Apples that have been bruised while frozen sometimes show soft, 

 water-soaked regions around the injured tissue, but the condition is 

 distinctly different from water core in both texture and location. 



Water core not only does not develop or spread in transit or 

 storage but in certain varieties such as Yellow Newtown and Wine- 

 sap may actually disappear after a few months' storage, particularly 

 if present only in a mild form. When large portions of the flesh are 

 affected, especially in soft-textured varieties like Jonathan, Delicious, 

 Stayman Winesap, and Rome Beauty, there is danger of subsequent 

 breakdown, and prompt disposal of the fruit is advisable (pi. 8, B). 



Partial control of the disease can be secured by regulating pruning 

 so as to avoid excessive exposure of the fruit to sunlight, by judicious 

 use of fertilizers to stimulate foliage growth and induce greater 

 shade, and by picking the fruit before it becomes overmature. (^^, 

 ^7, 66, 72, 80, 100, lU, IJiS, 186, IDS, 208.) 



PEARS 



AMMONIA INJURY 



Exposure to ammonia fumes may be responsible for injury to 

 pears. The trouble is first evident as reddish-brown rings around 

 the lenticels and at abrasions. Upon removal from the atmosphere 



181541°— 33 4 



