212 W. V. AGR. EXPERIMENT STATION [Bulletin 137 



to the one which causes this disease is known to occur in 

 Europe. He published a careful description of the disease and 

 its behavoir in 1906. 



His work was followed by a great deal of discussion as to 

 the cause and importance of the disease, and meanwhile the 

 chestnut trees were dying by thousands and tens of thousands. 



The Office of Forest Pathology at Washington, D. C., has 

 devoted considerable time to the study of this disease, especial- 

 ly as to its manner of spreading, distribution, and methods 

 of control. 



Pennsylvania was the first state to give the matter serious 

 consideration and more will be said of their work under an- 

 other heading. 



DESCRIPTION. 



The disease may attack a tree of any age, and any part of 

 the tree. It is caused by a fungus, and this seems able to 

 start its growth only in wounds of some sort, but when we 

 consider the squirrels, insects, and birds which may make 

 small wounds through the bark it is easy to see that there are 

 numerous points of entrance. 



It finds conditions most favorable for its growth just be- 

 tween the bark and the wood. Once started, it spreads rapidly 

 and soon girdles the part upon which it is growing. It is this 

 characteristic of girdling which makes it especially destruc- 

 tive. Only a small amount of tissue is actually invaded by the 

 fungus, but the entire tree, limb, or twig is killed beyond that 

 point. When a twig or limb is diseased, the spores or fruit- 

 ing bodies of the fungus are washed down toward the trunk, 

 which soon becomes infected and girdled. 



The disease is most noticeable during late spring and sum- 

 mer. During this period, the recently killed or dying limbs 

 are easily detected from some distance, on account of their dis- 

 colored foliage. The leaves on a diseased branch turn to a 

 reddish brown color, and finally wither, but they have a ten- 



