36 



which spread and finally extend over the whole fruit. The surface 

 then becomes dotted with dark, slightly elevated pustules, in which 

 the spores are borne (fig. 20, a, h.). At this stage of development this 

 disease is not easily distinguished from the early stages of black-rot 

 and bitter-rot. The berries do not shrivel up, however, as in the 

 case of the black-rot, and usually are easily detached from the bunch. 

 The spores mentioned are produced in large numbers and serve to 

 spread the disease. 



The fungus causing this disease is closely related to that which 

 pro4uces the bitter-rot of the apple, and by some is regarded as the 

 same; but no entirely conclusive cross-infection experiments have 

 yet been reported. The Department of Agriculture has demon- 

 strated by means of pure cultures of this fungus that there is another 

 stage, producing spores very similar in appearance to those just 

 mentioned, but borne in sacs which are inclosed in spore cases similar 

 to those of the black-rot fungus (fig. 20, c). This spore form is of 

 very infrequent or doubtful occurrence in vineyards, and is probabl}^ 

 not an important factor in the distribution of the disease. 



It is difficult to determine how much injury is done bj" this dis- 

 ease on account of the liability of confusing it with other fungous 

 troubles. It is quite generally distributed, and may cause more loss 

 than is usually attributed to it. 



Treatment. 



Spraying as recommended for black-rot will largely prevent this 

 disease. The later applications are especially important and should 

 be verv thorough. 



LESS IMPORTANT DISEASES. 

 Bitter-Rot. 



The bitter-rot of the grape is caused by a fungus known as Melan- 

 conium fuligineum. (Scrib. & Viala) Cav. Fruit attacked by this 

 disease presents an ajjpearance cjuite similar to that produced by the 

 ripe-rot. Bitter-rot is no doubt sometimes confused with other dis- 

 eases. It is mostly restricted to the Southern States, and is not gen- 

 erally regarded as serious. 



Treatment. — Spraying as for black-rot will probably prevent this 

 disease. 



White-Rot. 



The effect of the disease known as white-rot (ConiotJiyrium diplo- 

 dieUa (Speg.) Sacc.) upon the fruit of the grape is somewhat similar 

 to that of the brown-rot form of the downy mildew. It occurs in 

 Missouri and the Southwest and has been reported as rather serious 

 in some parts of Ohio. 



Treatment. — There is nothing in the nature of this disease, so 

 far as known, to indicate that it can not be satisfactorily controlled 

 by the treatment recommended for black-rot. Sufficient knowledge 

 of this subject to justify a positive statement in regard to treatment 

 is not at present available. 



284 



