GRAPE DISEASES 265 



cases on account of the fact that the same disease occurs on 

 apples, on which it is known as bitter-rot. 



Cause. 



Ripe-rot of* grapes is caused by the well-known fungus 

 Glomerella cingulata. The fungus occurs on a wide range of 

 plants, including many fruits. Its mycelium permeates the 

 affected tissues, and even enters the seeds of the grape-berry. 

 A cushion of mycelium develops just below the upper wall in 

 a group of epidermal cells. As it increases in size the cushion 

 the fruiting body pushes upwards, rupturing the epidermal 

 walls. In this way the fungus exposes its fruit-body to the 

 air ; spores are developed and may be liberated with little hin- 

 drance. The pathogene may readily pass from the grape to the 

 apple and back again. 



The fungus is favored by excessive humidity and hence is 

 most to be feared when such conditions prevail at the ripening 

 period. 



Control. 



The lateness of the attack of the fungus on grapes makes it 

 difficult to control. It is claimed, however, that if the later ap- 

 plications for black-rot are made thoroughly, the ripe-rot disease 

 will be largely prevented. (See page 235 for black-rot control.) 



More complete data concerning the fungus as it occurs on 

 apple are given on pages 14 to 21. 



REFERENCES 



Scribner, F. L. Bitter-rot of grapes. U. S. Agr. Comm. Kept. 1887 : 



324-325. 1888. 

 Galloway, B. T. Ripe rot of grapes and apples. U. S. Agr. Comm. 



Rept. 1890 : 408. 1890. 

 Lodeman, E. G. Some grape troubles of western New York. Ripe 



rot. Cornell Univ. Agr. Exp. Sta. Bui. 76 : 448. 1894. 

 Southworth, E. A. Ripe rot of grapes and apples. Journ. Myc. 6: 



164-173. 1891. 

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



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



Farmers' bul. 284 : 35-36. 1907. 



