B. P. I— 790. 



EXPERIMENTS IN THE CONTROL OF GRAPE 



ANTHRACNOSE. 



INTRODUCTION. 



Anthracnose of the grape, or bird's-eye rot, caused by the fungus 

 Sphaceloma am/pelinum De Bary, is a disease of considerable impor- 

 tance on certain varieties of grapes grown in the eastern United States. 

 While the disease does not seem to attack the Concord, which is the 

 most extensively grown of American varieties of grapes, Vergennes, 

 Salem, Diamond (Moore's Diamond), Norton (Norton's Virginia), 

 Missouri Riesling, Diogenes, Champion, and other varieties of both 

 wine and table grapes are very susceptible to anthracnose. In 

 serious outbreaks of the disease the fruit in a vineyard of one of 

 these susceptible varieties may be almost entirely destroyed and the 

 vines seriously damaged. Certain exceptionally fine varieties of 

 wine and table grapes can not be grown successfully in some localities 

 because of unusual susceptibility to it. 



Anthracnose affects practically all the green parts of the plant. On 

 the green shoots it causes cankers (PL I, fig. 3), which first appear as 

 small, light-brown, slightly sunken spots. These spots enlarge, sink 

 deeper, and become darker in color as the disease progresses. If the 

 canker is near the base of a shoot, the whole shoot may be killed. If 

 not killed directly by the disease, the shoot may be so weakened as to 

 be easily broken. The fungus causes cankers on the petioles and ribs 

 of the leaves (PI. I, fig. 2), on the stems of bunches of grapes, and on 

 the tendrils. On the grape berries it first appears as light-brown 

 spots, which rapidly become darker and are soon surrounded by a 

 circular bright-red zone, which, as seen against the green background 

 of the grape, presents the very striking appearance that gives the 

 disease the name of "bird's-eye rot." The berries in later stages of 

 the disease shrivel and dry up (PI. I, fig. 1). 



The fungus is also reported to be the cause of a leaf-spot. The 

 writer has, however, never observed any case of leaf-spot on grape 

 leaves that could be attributed to it. The fungus is supposed to live 

 over the winter in the old wood and in mummied grapes. It repro- 

 duces itself by means of minute, oblong, colorless spores, which 

 infect the young, green parts of the plant. The disease is well known 

 in Europe and, according to reports, may be controlled by proper 

 treatment. Very little has been done in America, however, toward 

 working out the best method for preventing the disease, and the 

 recommendations for its treatment in this country are usually based 



[Cir. 105] 3 



