DISEASES OF THE GRAPE 



231 



the most effective, and the first application should be given 

 about the time the young shoots are a foot long. The spray 

 ing should be continued throughout the summer at intervals 

 of two or three weeks until five or six sprayings have been 

 given. The number of sprayings that will be required will 



Fig. 102. — Black rot of the Niagara grape. (After Reddick, Cornell Bulletin 



No. 293.) 



depend largely upon the weather conditions. In regions 

 where the rain fall is abundant more spraying will be 

 necessary. 



Powdery Mildew. — The powdery mildew is also a native 

 of the United States. It is widely disseminated and now 



