G-rape. 297 



Black Rot ; cnaroon (Lcesradia Bidwellii, V. & R. ; PJioma uvicola, 

 B. & C.). Description. The name "black rot" has been com- 

 monly applied to this disease on account of the appearance of 

 the affected berries, these being of a deep black color. But the 

 fungus causing the rotting of the fruit also attacks other parts 

 of the plant. On the shoots it forms dark, oval areas, which 

 are slightly sunken. The centers of such spots are more or less 

 thickly studded with very small elevations or pimples, these 

 being characteristic of the disease, and by their aid the trouble 

 can in most cases be identified. Affected leaves turn to a dark, 

 reddish-brown color at the injured part. These portions are 

 generally found between the larger veins, and not centered 

 upon them, as in the case of anthracnose. Their outlines are 

 generally rounded. 



To the vineyardist such attacks are, however, of slight im- 

 portance as compared with those which injure the fruit. There 

 is probably no fungous disease of the grape which annually 

 causes greater losses than the black rot. Although each berry 

 must be separately affected, since the disease does not spread 

 from one to the other by means of the stems, yet the conditions 

 are generally so favorable that a large percentage of the crop is 

 annually lost. This applies particularly to southern vineyards, 

 for in them the disease is much more virulent than at the 

 North. In Xew York, the fungus is not generally serious, only 

 those regions being visited in which the climate is ameliorated 

 by bodies of water, or by other local conditions. Localities in 

 which the Catawba ripens well may be considered as subject to 

 the disease ; colder climates are comparatively exempt. 



Grapes which show the attacks of the black-rot fungus are 

 generally nearly or quite full grown (Fig. 59). It is therefore 

 during August and September that the disease is most to be 

 feared. If the berries are still green when the fungus gains an 

 entrance, the affected part turns a purplish brown, this color 

 gradually extending to the entire berry, which still retains its 

 form and firmness. The part first attacked gradually becomes 

 blackened, and characteristic pimples appear. At the same 

 time the berry shrivels and becomes strongly ridged, the seeds 

 projecting prominently under the drawn skin ; the entire berry 

 is then black, and minute elevations may be seen scattered 

 thickly over its surface, These changes may take place very 



