GRAPE PESTS AND THEIR CONTROL 



221 



The spores of the fungus are produced on this downy growth, 

 and under favorable conditions are distributed by wind and 

 water to all tender parts of the vine, where they germinate 

 and begin their work of destruction. The fruit is attacked 

 when partly grown, as shown in Fig. 45, becoming covered 



Fia. 45. Grapes attacked by downy-mildew. 



with the gray down of the fungus, the " gray-rot " of the 

 grape-grower. " If the berries escape the disease until half 

 grown, the fungus causes a brownish-purple spot that soon 

 covers the whole grape, giving the disease at this stage the 

 name of "brown-rot." Besides the summer-spores, another 

 form of reproductive bodies is produced in the winter to 

 carry the fungus through the resting period. 



Downy-mildew, like black-rot, spreads most rapidly and 



