178 DISEASES OF ECONOMIC PLANTS 



berries. Principal damage occurs to the fruiting canes, 

 the fohage of which suddenly wilts and dries. New canes 

 are frequently killed during the first season's growth. 

 The disease often starts in stubs exposed in pruning, and 

 progresses toward the root. 



Infection usually occurs through wounds, especially 

 pruning wounds, or those made by insects. Sometimes 

 the disease remains upon one side, while in other cases it 

 encircles the cane. 



Upon diseased canes the bark is lighter colored and 

 disfigured by smoke-colored patches of spores extruded 

 from the pycnidia within. The pycnidia appear as very 

 minute pustules. The wood is much discolored and even- 

 tually brittle. This cane blight is often attributed to a borer 

 or to drought or winter injury. 



The damage is often as high as 25 or 50 per cent of 

 the crop, and the disease is said to be present to some 

 extent in nearly all the raspberry plantations in New 

 York. Cuthbert, Marlboro, Ohio, Gregg, Kansas, and 

 the wild red raspberry are susceptible. Columbiana is 

 more resistant. 



The disease is disseminated largely by diseased nursery 

 stock or even in the dirt upon the roots of plants from 

 diseased fields, and is conveyed from plant to plant by 

 wind or rain, by pickers, and by workmen while pruning 

 and layering, also by tools in cultivation. See soil dis- 

 eases. Since the fungus can live on dead fragments of 

 canes, etc., upon the ground, these prove fruitful means 

 of propagating the pest. 



To prevent the disease care in the selection of healthy 

 plants and planting area is necessary. Plants should not 



