70 AMERICAN GRAPE GROWING 



wet weather, although any weakness of the vines caused 

 by overbearing, exhaustion of the soil, or other means, 

 may induce its development or increase its injurious 

 effects. The berries, when attacked by downy mildew, 

 seldom attain more than half size. The surface, after 

 the attack of the fungus, assumes a grayish color, which 

 soon turns to brown, thus producing a brown or gray 

 rot. The best preventive measures are to burn all in- 

 fected dry leaves and rubbish in the fall, and to thor- 

 oughly spray the vines in spring with Bordeaux mixture. 

 POWDERY MILDEW (Uncinula spitalis). Unlike 

 downy mildew, this disease nourishes with special energy 

 in dry, hot weather. It is not greatly destructive in the 

 Eastern and ^Northern States, but more so on the Pacific 

 coast. It draws its sustenance through filaments which 

 pierce the outer membrane of the leaves and fruit, and 

 presents the appearance of a dirty, powdery coating so 

 well known to vineyardists, rendering the grapes unfit 

 for market or for wine. The fungus is especially de- 

 structive in seasons of protracted drouth. In California, 

 where it is quite prevalent, the usual preventive is pow- 

 dered sulphur, dusted over and among the leaves, by 

 means of a fine wire sieve, or a bellows made for the 

 purpose. It is first applied when the young shoots are 

 about a foot long, and before blooming. Should it ap- 

 pear at a later period a second application will be neces- 

 sary. The disease often makes its appearance in June, 

 during the period of bloom, affecting the embryo shoots 

 and preventing their growth ; but more frequently, after 

 the vines have escaped an earlier attack, it appears dur- 

 ing protracted drouths, arresting the growth of the 

 young shoots and the development of the berries, 

 which crack, and attain only one-half their normal 

 size. The disease not only impairs the growth and 

 appearance of the grapes, but also prevents the fermen- 

 tation of the must, if they are pressed for wine. The 



