DISEASES OF THE GRAPE 219 



Powdery Mildew. — The powdery mildew is also a native 

 of the United States. It is widely disseminated and now 

 covers all of Europe. It is also known in every part of the 

 United States. This disease attacks all parts of the plant, 

 first appearing as white circular spots upon both the upper 

 and the lower surfaces of the young leaves. These spots 

 gradually enlarge and may finally cover the entire surface 

 of the leaf. The affected leaves are retarded in growth and 

 the blossoms which are attacked fail to set fruit. The 

 affected fruit ceases to grow and either falls off or fails to 

 ripen. 



The powdery mildew is strictly superficial and it is easily 

 rubbed off of the affected parts with the hand. Damp, rainy 

 weather favors its development, while dry windy weather 

 has a tendency to check it. The American varieties of grapes 

 are less susceptible to the powdery mildew than the European 

 sorts. 



There are two methods of controlling the mildew, namely, 

 dusting and spraying. In regions where the wind is light, the 

 dusting with flowers of sulphur on every part of the plant is 

 effective. Several applications of sulphur should be given. 

 The first application should be applied at the time the 

 blossoms begin to open. If signs of the mildew are observed 

 later, additional applications should be made at once. 

 Spraying with a 4-4-50 Bordeaux mixture is effective. If 

 the vines have been sprayed for the black rot this spray will 

 be effective in controlling the mildew. 



Downy Mildew. — The downy mildew somewhat resembles 

 the powdery mildew. It is widely distributed on both the 

 cultivated and the wild species of grapes. All parts of the 

 plant are affected, namely, the young shoots, the leaves and 

 the fruit. The injury is somewhat similar to that of the 

 powdery mildew. The same methods of control as recom- 

 mended for the powdery mildew are effective in controlling 

 the downy mildew, but perhaps Bordeaux mixture should 

 be given the preference. 



