GRAPE PESTS AND THEIR CONTROL 



221 



The spores of the fungus are produced on this downy o;r()wth, 

 and under favorable conditions are distributed by wind and 

 water to all tender parts of the vine, w^here they germinate 

 and begin their work of destruction. The fruit is attacked 

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



FiQ. 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 

 grow^n, 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 



