EXPERIMENT STATION BULLETINS. 



389 



not only in every plantation examined, but also on wild black raspberry plants 

 in this state. It was especially abundant in an old raspberry patch at the Agri- 

 cultural College but was found rather rarely in new plantations near the shore 

 of Lake Michigan. 



The disease attacks principally the fruiting canes, just before ripening of the 

 fruit, and causes the death of the upper portions of the branch and in severe 

 cases of the entire cane. The first evidence of its presence is shown by the wilt- 

 ing of the fruiting branches above the point affected. These soon dry up with 

 the immature fruit still left hanging. The canes become very brittle at the 

 diseased point while the wood is strongly discolored. The bark at these points 

 is usually lighter colored than surrounding portions and often shows a smutty 

 appearance due to a coating of spores. The spores are formed in minute pustules 

 (Pycnidia) buried in the bark, from which they ooze out on to the surface of 

 the cane. They are one-celled, egg-shaped bodies of a dark olive brown color 

 and are believed to be the chief means by which the disease is disseminated. 



All varieties of both red and black raspberries are subject to the disease, al- 

 though Cuthbert is mentioned as especially subject to it and Columbian one of 

 the least affected sorts commonly grown. 



Treatment. — As yet no successful spraying measures have been found. This 

 is possibly due to the fact that the canes do not hold any liquid substance readily, 

 the bloom causing water to roll off, hence Bordeaux mixture does not readily 

 adhere. Spraying the foliage does no good as the disease affects the canes only. 

 It is recommended, however, that the old canes be cut out and burned as soon 

 as the crop is gathered as well as all canes which show any signs of the disease. 

 New plantations should be started from healthy canes and on soil not recently 

 used for that purpose. 



LEAF-SPOT. 



(Septoria rubi Westd.) 



Fig. 39. — Blackberry leaf affected by the leaf spot fungus. (Original.) 



The New York Experiment Station Bulletin No. 226, Geneva, N. Y. 



