30 MISC. PUBLICATION 16 8, U.S. DEPT. OF AGRICULTURE 



can be observed more readily by removing the surface of the spot 

 with the thinnest possible paring. There will then be seen in the 

 flesh underneath a number of very small brown or black specks, 

 which are aggregates of cells killed by the fungus. These specks can 

 sometimes be seen through the cuticle but are more likely then to be 

 obscured by the surface discoloration. Owing to the collapse of the 

 cells in the affected area, the larger fruit spots become slightly 

 sunken. On overripe apples the spots are often surrounded by a 

 band of brown. 



Because of their speckled appearance, fruit spots caused by Myca- 

 sphaerella are easily distinguished from all other spot diseases of 

 apples. They are further distinguished from bitter pit by not being 

 markedly sunken except in later stages, by occurring only in the 

 epidermis of the fruit, and by having no connection with the water- 

 conducting system. 



On fruit in cold storage the spots change but little. In delayed or 

 cellar storage new spots may appear and older ones may seem to 

 enlarge slightly. In the main this latter change results from the 

 change in color of the fruit rather than from the actual enlargement 

 of affected areas. 



Infections on the fruit appear not earlier than June and may con- 

 tinued until August. Bordeaux mixture or lime-sulphur sprays 

 are effective in controlling the disease. (i4, iJ, 16^ 22^ 100^ IH^ 

 131, U6, 195, 208, 227, 232a.) 



GRAY-MOLD ROT 



{Botrytis spp.) 



Gray-mold rot occurs on apples from the Pacific Northwest and 

 from various producing sections in the eastern United States. It is 

 not common on the market, however, and is seldom as destructive on 

 apples as on pears. 



As seen on apples from the Northwest, gray-mold rot is charac- 

 terized by diseased areas that at first have a pale, translucent, watery 

 appearance but soon change to a duller brown. In the early stages 

 of the rot there are dark-brown spots around the lenticels about 

 one eighth of an inch in diameter, which in their final form become 

 reddish brown and have a pale or whitish center. These spots are 

 most marked when the rot develops at low temperatures, and con- 

 tinue to give the fruit a " freckled " appearance even after it is 

 completely rotted. 



On northwestern fruit the disease has been found as early as 

 November in common storage but usually not before February in 

 cold storage. The Winesap variety seems to be affected more often 

 than any other. 



In gray-mold rot of eastern apples the affected tissues are charac- 

 teristically light brown and rather soft, as. in the northwestern form ; 

 no dark-brown or reddish-brown spots have been seen at the lenticels 

 in diseased areas, however, and the name " spot rot " cannot properly 

 be used, in the sense in which it is applied to the northwestern 

 form. In the East the disease has been found on several of the 

 more important commercial varieties. 



