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MANUAL OF FRUIT DISEASES 



Symptoms. 



On the upper surface of the leaf the first signs of downy-mildew 

 are in the form of small greenish yellow indefinite spots, the 

 margins of which gradually merge into the darker green of 



FIG. 61. Downy-mildew on lower surface of grape-leaf. 



the leaf. In a short time there appears within the spot a net- 

 work of small, reddish brown lines, the discolored smaller 

 veins. These lines become more pronounced until the whole 

 diseased portion is brown, dry and brittle, and eventually 

 cracked. These symptoms apply particularly to susceptible 

 leaves. On the foliage of the more resistant vines there occurs 



