DISEASES OF SHADE AND FOREST TREES. 



101 



CHESTNUT BARK DISEASE OB BLIGHT. 



This is probably the most serious tree disease in America 

 at the present time. It is caused by a fungus (Diaporthe 

 l><; i'i.<iiica * ALurrill) which lives parasitically in the bark, 

 -IK ling its minute thread-like processes in all directions from 

 the point of attack until the trunk or branch is completely 

 girdled. (Figs. 37, 38.) 



It is very doubtful if the fungus can gain entrance to a 

 tree except through wounds, and it is probably carried from. 



Fig. 38. Section of Chestnut tree killed 



by blight with bark in successive 



stages of decay and pustules in 



which the winter spores 



are borne. ( Photo by 



J. F. Collins.) 



place to place by boring insects and by birds (especially wood- 

 peckers ) . It is also carried on infected timber shipped into 



*The proper name of this fungus is at the present time a disputed point 

 which will require further study before it can be definitely settled. 



