30 



appear; these spread and soon affect the whole berry, which becomes 

 black and shriveled, as shown in the accompanying illustration (fig. 

 11). These diseased berries remain attached to the vine, and their 

 surfaces become covered with minute black pustules, which contain 

 the summer spores of the fungus. During the winter and spring 

 another form, called the winter, or resting spore, is produced upon 

 these old, shriveled berries (fig. 10, c, d). These spores help to carry 

 the disease over from one season to another. This fact would indi- 

 cate the desirability of destroymg, by burning, all diseased fruit, as 

 well as leaves and prunings, as early in the spring as possible. 



Treatment. 



This disease can be effectually con- 

 trolled by thorough spraying with Bor- 

 deaux mixture. Five or six applications 

 are usually necessary during the season, 

 the first being made just before the buds 

 open. For the last one or two applica- 

 tions, some fungicide which does not 

 stain the fruit should be used . Burgundy 

 mixture is recommended for this purpose. 

 Full directions regarding the preparation 

 of the fungicides and the times of appli- 

 cation will be found later. 



Covering the bunches of grapes with 

 paper bags soon after the blossoms fall 

 is a means of preventmg black-rot and 

 most other fungous parasites. It is usu- 

 ally regarded as too laborious and expen- 

 sive for large vineyards, but may be 

 profitably practiced where only a small 

 number of vines are grown. 



DOWNY MILDEW. 



Downy mildew (Plasmopara viticola 

 (B. & C.) Berl. & De Toni) in certain 

 seasons and in northern localities some- 

 times causes more loss than black-rot 

 and is a close rival for first place among 

 the fungous enemies of the grape. It 

 attacks all the tender growing parts of 

 the vine. Usually it is at first most noticeable on the foliage, pro- 

 ducing greenish yellow, irregular spots upon the upper surface, which 

 become reddish brown. At the same time there appears on the under 

 surface of the leaf a thin, loose, white, downy growth, suggestive of 

 hoar frost (fig. 12). This growth consists of the fertile fungous fila- 

 ments bearing the summer spores (fig. 13, a, h), which under favorable 

 conditions are distributed by the wind and water to the berries and 

 other parts, where they germinate, penetrate the tissues, and con- 

 tinue their destructive work. The young shgots are also frequently 

 attacked and killed, 



284 



Fig. 11.— a bunch of grapes destroyed 

 by black-rot. 



