FUNGUS DISEASES. 233 



destructive fungi attacking the grape in this country, 

 and in doing that 1 shall avail myself of an excellent 

 report on "Fungus Diseases of the Grape, and Their 

 Treatment," by B. T. Galloway, chief of the division of 

 Vegetable Pathology, U. S. Department of Agriculture. 



"There are but four fungus diseases of the grape in 

 this country which occasion sufficient damage to warrant 

 our attention, and they are (1), The grape Peronospora, 

 or downy mildew ; (2), powdery mildew ; (3), black rot ; 

 and (4), anthracnose." 



Grape Peronospora, or Downy Mildew, Brown 

 Rot and Gray Rot. The fungus causing these diseases 

 is known to botanists as Peronospora viticola. It 

 attacks the leaves, young wood, flowers and fruit. On 

 the leaves it usually manifests itself first in the form of 

 greenish yellow, or brownish spots on the upper surface, 

 while on the lower side corresponding parts are covered 

 with a white, frost-like growth. As the disease pro- 

 gresses the frost-like patches may disappear, leaving 

 only the brown leaf, which soon dries up and falls off. 

 Young wood and flowers are affected in the same way, 

 and the young berries, if attacked, usually cease growing 

 and appear as shown in Fig. 94. This form of the dis- 

 ease is known as the downy mildew, and in some sections 

 it causes the only serious damage. On the fruit the 

 fungus occurs in two forms, causing what is known as 

 brown, or gray rot. The former disease, as a rule, does 

 not make its appearance until the berries are nearly 

 grown. At this time a brownish-purple spot will appear 

 on one side of the berry, and in a short time the whole 

 fruit is involved, turning brown, and ultimately becomes 

 soft and wrinkled. In gray rot the fruit is covered with 

 the same frost-like growth seen on the leaves. The ber- 

 ries are literally plastered together with the fungus. 



Powdery Mildew ( Uncinula spiralis). This usu- 

 ally appears about midsummer, attacking the leaves, 



