EXPERIMENT STATION BULLETINS. 



383 



color and delicate while those of the mushroom are dark brown or black on the out- 

 side. These fungi spread by means of their underground mycelium as well as 

 by spores. Vines which are on poorly drained soil are most apt to suffer from 

 root rot. Good drainage and the prompt removal of diseased plants are recom- 

 mended as preventatives. 



Leaf blight (Cercospora viticola (Ces.) Sacc.) causes irregular dark brown 

 spots of dead tissue on the leaves of the grape. It occurs in most of the eastern 

 states but is not usually found to be severe in the more northern portions of 

 this region. It is apparently of little importance to the grape growers of Michi- 

 gan. 



CURRANT DISEASES. 

 Leaf-spot (Septoria ribis Desm. and Cercospora angulata Wint.) 



Fig. 33. — a. Leaf of currant affected with the leaf spot disease; b. a spore producing pustule 

 magnified, from a diseased spot of a leaf, giving out long, slender spores, a few of which are 

 i shown highly magnified at c. (Original.) 



The fungi causing leaf-spot of currant and gooseberry are common and de- 

 structive to the foliage in this state. Affected leaves at first show small brownish 

 spots during June or July and by August the foliage begins to drop. It is not 

 unusual to see bushes entirely defoliated by this disease long before frosts. 

 Thus the plants are prevented from making a complete growth or of properly 

 perfecting the fruit buds. The spores of these diseases are produced on the 

 dead portions of the diseased leaves on which the fungi also hibernate. 



Treatment. Rake and burn all dead leaves and rubbish in spring. It has been 

 found possible to reduce the attacks of these fungi to a great extent by the use of 

 fungicides applied at intervals of two or three weeks, during the growing season, 

 the first application to be made early in June. Even two or three applications 

 will materially reduce this trouble. The spray used early in the season, while 

 the fruit is on, should be one of the clear mixtures so as to avoid staining the 

 berries. After harvest Bordeaux mixture may be substituted. 



ANTHRACNOSE OF CURRANTS. 



(Gloeosporium Ribis (Lib.) Mont. & Desm) 



This disease causes a spotting of the leaves of the cultivated currant but seems 

 less common than the previously mentioned fungi. Its first appearance is made 

 early in summer and like the other leaf-spot fungi causes the leaves to turn yellow 

 and fall off prematurely. The fungus itself produces small brownish spots on the 

 foliage and in the diseased areas the spores are produced. They are one-celled 

 curved bodies of minute size. 



Treatment. — If the bushes are treated as for the leaf-spot fungi the anthracnose 

 should not be troublesome. 



