336 



Minnesota Plant Diseases. 



"Repeated sprayings with bordeaux about every ten days 

 during a season, beginning at least by the middle of July, is 

 useful in keeping this disease in check." The number of spray- 

 ings is dependent on the season. In very wet seasons more 

 may be necessary. If the under surfaces of the leaf can be 

 sprayed, the results will be most successful, but great gain is 

 possible by the ordinary method of spraying. 



Downy mildew of beans, peas, etc. (Phytophthora phaseoli 

 Thaxt.). A downy mildew frequently attacks cultivated beans 

 and closely related plants and may create a very serious amount 



FiG. 169. Downy mildew of muskmelon, showing the under surface of an attacked leaf. 



After Clinton. 



of damage. The summer spores are produced in a similar man- 

 ner to the blight of potatoes. The young stems, leaves and 

 pods are attacked. The downy patches on the pods are usually 

 dense, woolly growths, whitish in color, while those on the 

 stems and leaves are less dense. As with most downy mildews, 

 moist seasons or moist situations favor the growth of the dis- 

 ease. 



Diseased plants should be burned to prevent the recurrence 

 in following seasons. "As the fungus usually appears first and 

 most vigorously in low, moist places, the land used should be 

 high or well-drained. Spraying, beginning with bordeaux and 



