B, P.1,—847, 
THE IMMUNITY OF THE JAPANESE CHESTNUT 
TO THE BARK DISEASE. 
By Haven Mercazr, Pathologist in Charge of the Laboratory of Forest Pathology. 
rd 
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 Ji ersey, 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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