3 68 



Minnesota Plant Diseases. 



"If after two or three days there remain portions which are 

 unchanged in color the vineyard is treated a second time, partic- 

 ular attention being paid to the parts omitted at the first treat- 

 ment." Lodeman (The Spraying of Plants, p. 295.) 



Downy mildew of vines [Plasmopara viticola (B. &C.) Berl.]. 

 This is a very destructive disease of vines originating in the 

 United States, but since about 1878 causing enormous destruc- 



KIG. 19(i. Downy mildew of grape. Under surface of a leaf, showing down of mildew 

 threads spread over the entire leaf. Original. 



tion of vines in Europe. The fungus is a downy mildew and is a 

 destructive parasite. It appears on all above-ground parts of 

 the vines, but most abundantly on the leaves. \Yhen the latter 

 are attacked they show, from above, pale green spots which later 

 become light yellow in color. This is the region where the my- 



