368 



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- 

 tilar 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- 



VlG. 196.— Downy mildew of grape. Under surface of a leaf, showing down of mildew 

 threads spread over the entire leaf. Original. 



lion 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. When 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- 



