MARKET DISEASES OF FRUITS AND VEGETABLES 13 



fruit, especially that of early-maturing varieties, can be expected 

 to develop bitter pit during the transit and marketing period im- 

 mediately after harvest. The disease does not spread from one 

 fruit to another, but pits may enlarge and new pits may develop 

 during transit on apples removed from cold storage. 



(See 1, 12, 13, 21, 22, 31, U3, 59, 61, 62, 65, 79, 95, 99, 100, 113, 

 lilt, 12U, 136.) 



Bitter Rot 

 (Glomerella cingulata (Ston.) Spauld. & Schrenk) 



OCCURRENCE AND SYMPTOMS 



Bitter rot is principally a disease of apple, though it may occur 

 on pear, peach, quince, and cherry. It may occur in practically 

 all apple-growing sections east of the Great Plains, but it typically 

 occurs, in hot, humid districts. It is most common and most 

 destructive from Arkansas and southern Missouri eastward to 

 Virginia and farther south. Even there it is irregular in occur- 

 rence, being worse in warm, wet growing seasons. 



The disease usually appears in the orchard in late June or 

 early July. It becomes most serious on well-developed fruit in 

 August and September; hence the name "ripe rot" is sometimes 

 applied to it. Susceptible varieties include Yellow Newtown, De- 

 licious, Golden Delicious, Yellow Transparent, Jonathan, Winesap, 

 and Ben Davis. 



Bitter rot is characterized by brown, definitely limited spots 

 varying in size from mere specks to lesions involving the whole 

 side of an apple. Rots developed in the orchard about harvesttime 

 are not sunken at first and are generally marked by narrow, con- 

 centric zones of light and brown color. Eventually the spots 

 become sunken, but they remain relatively firm. Spots % inch 

 in diameter or larger usually show spore masses that may or may 

 not be arranged in concentric circles. Under orchard conditions 

 these spore masses are at first pink or cream-colored; eventually 

 they become gray or almost black (pi. 6, A). 



Bitter rot is sometimes found on apples in storage and during 

 the period of marketing after the fruit is removed from storage. 

 Slight infections existing when the fruit is stored continue to 

 enlarge in storage until the fruit temperature reaches 50° F. 

 Rot development is arrested then; but the fungus remains alive 

 and, when the apples are removed from storage, the rotted areas 

 enlarge. The decayed spots in storage are usually small, ranging 

 from *4 to % inch in diameter. They are flat or slightly sunken, 

 firm, and of a uniform, medium-brown color. Rotten spots found 

 after the fruit has been removed from storage are usually larger 

 and more sunken and often produce wet pink or cream-colored 

 spore masses (pi. 6, B). The more or less concentric arrange- 

 ment of the spore masses distinguishes the disease from black 

 rot, in which the spore-producing bodies (pycnidia) are always 

 black and scattered irregularly over the diseased area. 



CAUSAL FACTORS 



The disease is spread by means of spores, which are produced 

 in immense numbers during the growing season on bitter rot mum- 

 mies of the preceding year or on cankers caused by the fire blight 



