MARKET DISEASES OF APPLES, PEARS, QUINCES 31 



Gray-mold rot of apples is caused by two, possibly three species of 

 Botrytis^ one of which is apparently the same as that found on 

 pears. On apples, as on pears, the fungus is able to grow from dis- 

 eased fruits to healthy ones lying near or touching them, and its 

 growth is not entirely checked even by a temperature of 32° F. 



The only control measures that can be suggested are careful hand- 

 ling of fruit and the frequent removal of all decaying fruit and 

 other culls from the packing house and its immediate surround- 

 ings (p. 3). It is probable that the copper-treated wraps used for 

 controlling gray-mold rot of pears (p. 53) w^ould be of value for 

 control of the rot on apples. The injury that may be caused by 

 the use of such wraps is discussed on page 53. {17^ 22^ I^^ JjS, 9%^ 

 100, 101, 195.) 



HAIL INJURY 



Early-season hail injury generally occurs at the blossom end or 

 on one side of the apple, but only because of the position assumed 

 by the fruit on the tree during this period. Later, when the fruit 

 has become larger and heavier it generally turns downward, so that 

 hail marks on well-developed fruit are more often made on the 

 stem end. 



Fruit injured early tends to outgrow the internal condition pro- 

 duced, but may become slightly misshapen as it develops. When 

 fruit is struck by hail late in the season, the cuticle covering the 

 affected spot may be cracked or torn but often remains intact. Such 

 spots range from one fourth to one half inch in diameter, are 

 slightly sunken, and the flesh beneath them is brown and somewhat 

 spongy and dry because of loss of water from the bruised area (pi. 

 7, C). The spots are usually dry enough when the fruit is shipped 

 so that they are not followed by decay, even though there are cracks 

 in the skin and flesh. 



Hail injury can be distinguished from other spots described in 

 this publication by the fact that only the upper exposed part of 

 the fruit is affected. This usually coincides with the blushed area, 

 except on fruits injured by hail while still young and small. 



HEAT INJURY 



IN THE ORCHARD 



Apples may be injured while still on the tree by excessively high 

 temperatures following a period of relatively cool weather. The fact 

 of injury is indicated by various symptoms, chief among which are 



(1) a dwarfing or distortion of the fruit (pi. T, A, E; ]3l. 9, A, B) ; 



(2) the development of brown spongy or corky streaks in the flesh 

 (pi. 9, C, D) ; (3) browning of the flesh around the core; (4) brown- 

 ing and collapse of the tissue beneath the skin, making an almost 

 complete layer of dead tissue surrounding the sound interior portion 

 of the apple. 



It is believed probable that heat injury and drought injury are 

 closely related and gradually shade into each other. This hypothesis, 

 however, does not eliminate heat as the significant factor initiating 

 the four injuries listed above. 



