56 MISC. PUBLICATION 168, U. S. DEPT. OF AGRICULTURE 



ing an arid or semiarid climate. Among the most susceptible 

 varieties are Yellow Transparent, Rambo, Tompkins King, Jona- 

 than, Delicious, Stayman, Winter Banana, Arkansas (Mammoth 

 Black Twig), and Winesap. In the Northwest the last-named 



variety is more often affected than any other. 



Water core is a nonparasitic disease characterized by water- 

 soaked regions in the flesh of the apple. When water core is 

 severe, these areas are hard and glossy. The disease is more 

 commonly found near the core and around the primary vascular 

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

 the whole of it (pi. 10, G, H). When only the core area is involved 

 it is impossible to detect the disease without cutting the fruit 

 (pi. 10, F). Visible water core is frequently associated with 

 sunburn. 



Water core is particularly bad in sections where heat and 

 sunlight are intense. High temperatures at the time the apples 

 are approaching maturity are especially favorable to its develop- 

 ment. The disease is most likely to occur in fruit that is freely 

 exposed to the sun. It often increases rapidly as apples become 

 overmature. Apple tissues affected with water core are distinctly 

 different in both texture and location from the soft, water-soaked 

 tissues adjacent to spots bruised while the apples were frozen. 



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

 storage, but in certain varieties such as Yellow Newtown and 

 Winesap it may actually disappear after a few months' storage, 

 particularly if originally present in only a mild form. When large 

 portions of the flesh are affected, especially in soft-textured 

 varieties like Jonathan, Delicious, Stayman, and Rome Beauty, 

 there is danger of subsequent break-down and prompt disposal 

 of the fruit is advisable. 



Control of the disease is mainly by picking fruit before exten- 

 sive water core develops. Near harvesttime growers should ex- 

 amine the fruit for presence of water core, particularly fruit well 

 exposed on the southwest side of the tree, and start picking if 

 appreciable water core is developing. 



(See 12, 15, ho, 59, 65, 11J>.) 



PEARS 

 Ammonia Injury 



Exposure to ammonia fumes may cause injury to pears. The 

 trouble is first evident as reddish-brown rings around lenticels 

 and at abrasions. Upon removal from an atmosphere containing 

 ammonia the skin color soon changes to black (pi. 11, F). In mild 

 cases the injury does not extend beyond the tissue immediately 

 beneath the epidermis. With more severe exposure the lenticel 

 spots may become much enlarged and finally coalesce and the 

 discoloration may extend deep into the flesh. 



The presence of moisture is favorable to ammonia injury; pears 

 with moist surfaces are more susceptible than those that are 

 badly wilted or those that have dry surfaces. Immature pears 

 have been found more susceptible than mature ones. 



(See 68, 110.) 



