[Reprint of Bureau of Plant Industry Bulletin No. 121, Pt. VI, issued Feb. 10, 1908.] 
THE IMMUNITY OF THE JAPANESE CHESTNUT TO THE BARK 
DISEASE. 
By Haven Merca.r, Pathologist in Charge of the Laboratory of Forest Pathology. 
Tur 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 ebserved, 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 ImmMuNE VARIETY. 
Observations made by the writer during the past year indicate that 
all varieties and species of the genus Castanea are subject to the dis- 
ease except the Japanese varieties (Castanea crenata Sieb. and Zucc.). 
All of the latter that have been observed in the field or tested by inocu- 
lations 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. Sime of these may prove later to be 
subject to the disease. Immunity tests of all known varieties of chest- 
nuts have been undertaken. 
Attempts will also be made to hybridize the Japanese with American 
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 cer- 
tainly will not take the place of the American chestnut. he tree is 
said to attain a height of 50 or 60 feet inJapan. As seen in this coun- 
try, it is a handsome tree, dwarfish and compact in habit, and rather 
slow growing. It has hardly had time to show how large it can grow. 
_ The immunity of the Japanese chestnut, together with the fact that 
it was first introduced and cultivated on Long Island and in the very 
locality from which the disease appears to have spread, suggests the 
interesting hypothesis that the dasnsp was introduced from Japan. 
So far, however, no facts have been adduced to substantiate this view. 
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