GRAPE DISEASES 261 



but it neither blackens nor shrivels into prominent ridges as in 

 the case of black-rot. 



Cankers are formed on the peduncles. These are brownish, 

 depressed areas which may enlarge continuously until the part 

 is girdled. This results in a withering of the berry, as already 

 noted. 



Cause. 



The causal fungus is referred to as Coniothyrium diplodiella. 

 It is claimed by certain French authorities that at least one other 

 form (sexual) exists in that country, and therefore the proper 

 name should be Charrina diplodiella. 



The mycelium of the fungus is abundant in the lesions, 

 particularly those on the berries. Sometimes the seeds are 

 affected. In the peduncles the mycelium causes the death of 

 the tissues as a result of which the berries wither. About the 

 time grapes begin to ripen pycnidia are produced. These arise 

 as a result of a special growth of the mycelium ; a cushion is 

 developed in which a cavity bearing spores is finally formed. 

 These fruiting bodies lie beneath the cuticle until maturity, 

 when they burst forth, first appearing as shining, rosy 

 points, then white and ultimately brown in color. Although 

 perithecia have been reported in France, they are unknown in 

 America. 



Control. 



It is doubtful whether special treatment for white-rot is 

 ever necessary. The disease should be controlled by the black- 

 rot spray-schedule ; at least there is nothing to indicate the 

 contrary. 



REFERENCES 

 s 



Quaintance, A. L., and Shear, C. L. Insect and fungous enemies of 

 the grape east of the Rocky Mountains. White-rot. U. S. Agr. 

 Dept. Farmers' Bui. 284 : 36. 1907. 



Scribner, F. L. White rot. U. S. Agr. Comm. Rept. 1887 : 325-326. 



1888. 



