B. P. I.— 347. 



THE IMMUNITY OF THE JAPANESE CHESTNUT 

 TO THE BARK DISEASE. 



By Haven Metcalf, Pathologist in Charge of the Laboratory of Forest Pathology. 



THE EXTENT OF THE BARK DISEASE. 



The bark disease of the chestnut, caused by the fungus Diaporthe 

 parasitica Murrill, has spread rapidly from Long Island, where it was 

 first observed, and is now reported from Connecticut, Massachusetts, 

 Vermont, New York as far north as Poughkeepsie, New Jersey, Penn- 

 sylvania, and possibly Delaware. It is no exaggeration to say that it 

 is at present the most threatening forest-tree disease in America. 

 Unless something now unforeseen occurs to check its spread, the com- 

 plete destruction of the chestnut orchards and forests of the country, or 

 at least of the Atlantic States, is only a question of a few years' time. 



AN IMMUNE VARIETY. 



Observations made by the writer during the past year indicate that 

 all varieties and species of the genus Castanea are subject to the 

 disease except the Japanese varieties (Castanea crenata Sieb. and 

 Zucc). All of the latter that have been observed in the field or 

 tested by inoculations have been found immune. This fact can 

 hardly fail to be of fundamental importance to the future of chestnut 

 nut culture. Although the nuts are distinctly inferior in flavor to the 

 European varieties, such as Paragon, the Japanese chestnut is 

 already grown on a large scale as a nut-producing tree. There are, 

 however, many trade varieties of dubious origin. Some, of these 

 may prove later to be subject to the disease. Immunity tests of all 

 known varieties of chestnuts have been undertaken. 



Attempts will also be made to hybridize the Japanese with Ameri- 

 can and European varieties, with the hope of combining the immunity 

 of the former with the desirable qualities of the latter. 



However excellent as a nut and ornamental tree, the value of the 

 Japanese chestnut as a forest tree is doubtful. It can be recom- 

 mended only experimentally at present for forest planting. It 

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