232 



MANUAL OF FRUIT DISEASES 



The name black-rot, which is in use in America and Europe, 

 applies to the condition of affected grapes (Fig. 59) . When the 

 berries are about one-half grown, the disease shows its first 

 symptoms in the form of a blanching. This is soon re- 

 placed by a whitening 

 of the diseased area, 

 which is now more evi- 

 dent. A brownish line 

 appears at the margin, 

 and there results, on ac- 

 count of a light-colored 

 circular disk with an 

 encircling darker band, 

 a bird's-eye effect. 

 Some grape-culturists 

 confuse this stage with 

 the true bird's-eye, or 

 anthracnose, described 

 on page 250. The spot 

 increases in size rapidly 

 and its surface becomes 

 sunken. In a few hours 

 after the beginning of 

 the development of the 

 lesion, numerous minute 

 brown specks appear on 

 the light-colored center. 

 These are the fruiting 

 bodies of the black-rot 



organism, which very shortly become so numerous as to give 

 the spot a blackish aspect. Occasionally the extent of the 

 lesion is halted, and in a few days there is formed a thin black 

 superficial crust on the side of the berry. The usual course of 

 development, however, is for the berry to become entirely in- 



FIG. 59. Black-rot on grape berries. 



