CHAPTER XVI 

 CHESTNUT DISEASES 



The chestnut was until recently one of the important forest- 

 trees of New York, Connecticut, Pennsylvania and the Alle- 

 ghany Mountain region southward to Alabama. Besides its 

 commercial value as timber, the chestnut was important also 

 in its natural range as a much-favored ornamental. As an 

 orchard-tree, the varieties of the American and foreign, species 

 are of relatively less importance. 



Fifteen years ago the chestnut was not subject to any very 

 destructive diseases. With the appearance of the Endothia 

 canker or blight, however, the very existence of the species 

 seemed threatened. During the &st ten years of the spread 

 of the fungus causing this disease, all the chestnut trees over 

 hundreds of square miles were killed. The disease is now 

 prevalent over practically the entire range of the chestnut 

 and apparently only a negligible niunber will escape destruction. 

 It is unusual for a parasite to be so adapted that all the individuals 

 are equally susceptible to its attack. Many limiting factors 

 of resistance, temperature, moisture, seasonal conditions, dis- 

 seminating agents and the like serve to hold parasitic fungi 

 in check. The fungus causing the canker, however, is the 

 extreme example of an introduced parasite which is perfectly 

 adapted to the host and the environmental conditions of eastern 

 United States. 



With the passing of the chestnut, it is scarcely necessary to 

 consider other less important diseases of this tree. Several 

 leaf-spot diseases are common on chestnut. In the North 



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