124 A MANUAL OF FORESTRY 



B. FUNGI. 



CHESTNUT BARK DISEASE (Diaporthe par a silica). 



\\ithout doubt this is one of the most threatening fungous 

 diseases which ever attacked a forest tree. It is one of the few 

 diseases which cause the certain death of healthy, vigorous trees. 

 So virulent is it that the chestnut, on which it preys, has been 

 practically exterminated in portions of New England, New York, 

 Pennsylvania and New Jersey. The worst injury has been 

 done on Long Island, and in the vicinity of New York City, 

 from which as a center it is spreading. Only since 1905, has 

 the disease been generally recognized, and in New England it 

 was little noticed until 1907. Southwestern Connecticut is the 

 most seriously infected region here; and in Fairfield and New 

 Haven counties the chestnut has been nearly all killed. As we 

 proceed from southwestern Connecticut, through that state and 

 then into Massachusetts and northern New England, the number 

 of infected trees is less and less noticeable. But the disease may 

 be found practically over the entire New England range of the 

 species. 



The chestnut bark disease attacks and kills the cambium 

 layer, which lies between the bark and the wood. This is the 

 growing layer of the tree, and when it is girdled, death of the 

 portion above the injured place results. As the disease is 

 distributed by the spores (virtually seeds) which are easily 

 blown by winds, or carried by birds, its spread is rapid. These 

 spores cannot attack a tree except through a wound, but as 

 every tree has many slight wounds or openings in its bark, it 

 is rarely that a tree is exempt from the disease. When a spore 

 finds lodgment it quickly develops a fungous growth spreading 

 in the cambium layer at first in a somewhat elliptical form until 

 finally it girdles the branch or trunk. It may also work up and 

 down the trunk. 



Trees of all ages from the young sprout to those of lumber 

 value are attacked. In an old tree with thick bark the disease 

 usually enters at the top and works downward. On young trees, 



