356 FUNGOUS DISEASES OF PLANTS 



this point it gradually works downward, killing first the uppermost branch, 

 then the next lower one, and so on until by the close of the berry harvest one- 

 half of the cane or more may be dead. On black caps the disease also shows 

 a tendency to work down one side of the cane, killing the bark and discolor- 

 ing the wood on that side, while on the other side the bark remains green. 



The disease occurs both upon black and red varieties of the 

 raspberry, and it is thought that it may also injure dewberries. 

 Cuthbert, Marlboro, Ohio, Gregg, Kansas, Superlative, I.X.L., 

 and Pride of Geneva are varieties of raspberry which have been 

 found to have been much injured in New York, while Columbian 

 has proved notably resistant. The amount of damage which may 

 be done when nonresistant sorts are grown is commonly estimated 

 at from one fourth to two thirds of the crop. The disease doubt- 

 less spreads most rapidly during moist, warm 

 summers, but its destructive effects upon the 

 fruit crop are particularly noted during a sea- 

 son of drought. 1 



The fungus. By the time that a cane is com- 

 pletely wilted there may be found at the base 

 of the wilted portion a short area dead and 

 discolored, in which appear the pycnidia. When 

 Fig. 174. Conwthy- expelled from the pycn j d i a the spores form 



rium Fuckelii. (After J r 



Stewart) brownish patches on the dead bark, or the 



dying canes might have a smutty appearance 

 from the presence of numerous spores. Viewed singly the spores 

 are very lightly colored, but in mass the brown color is pronounced. 

 The spores measure 2.4-5 X 2-3.5 A* (Fig- 174). Pure cultures of 

 this fungus were obtained, but a description of growth characters has 

 not yet appeared. Results from most carefully conducted inocula- 

 tion experiments made from pure cultures have clearly demon- 

 strated the parasitic nature of the disease, and the independence 

 of Coniothyrium in producing it. 



1 Clinton thinks (Conn. Agl. Exp. Sta. Rept. (1906) : 321-324) that the raspberry 

 cane blight fungus gains entrance through the flowers and young fruit, the spores 

 apparently being spread by bees and other insects. In Connecticut the black 

 cap varieties have been more susceptible, special complaint having been made of 

 serious injury to the Parmer, Cumberland, and Kansas. It has also, however, in- 

 jured red varieties and occurs on wild black raspberries in the same region. He 

 presents no further proof of the connection with Leptosphasria, but refers the 

 fungus to that genus under the name Leptospharia Coniothyrium (Fckl.) Sacc. 



