THE CHESTNUT BARK DISEASE 
An Undesirable Immigrant Which Has Secured Firm Foothold in Eastern 
United States—Breeding Resistant Species Probably the Only 
Solution of Problem—Opportunity for Orchardists On 
Pacific Coast to Build Up Industry. 
Haven METCALF 
In charge of Forest Pathology Investigations, Bureau of Plant Industry, U. S. 
Department of Agriculture, Washington, D. C. 
China, in the province of Chili, 
east of the Great Chinese Wall, 
and four or five days’ journey by 
bullock cart from Peking, there is 
a little-known section of mountainous 
country. Here a species of chestnut, 
the exact identity of which is not yet 
known, but which may possibly be 
Castanea mollissima, grows ,wild on the 
mountain slopes and valleys and is also 
cultivated by the Chinese for its nuts 
(fig.1). These chestnut trees have a 
disease which in appearance is somewhat 
like the European apple canker, as it 
occurs in America on apple trees. So 
far as we know it does relatively little 
harm to the chestnut trees of China, 
simply producing permanent cankers on 
some of them, killing a few limbs, and 
probably occasionally killing young 
trees. There is no reason to suppose 
that the Chinese ever had any clear 
cognizance of it as an especially harmful 
agent, and it does not appear to be 
conspicuous enough to have attracted 
the attention of even the observing 
traveler, until it was discovered this 
summer by Frank N. Meyer, of the 
United States Department of Agri- 
culture. Probably it is not more con- 
spicious than certain canker diseases of 
junipers in America, which have only 
recently been recognized and described. 
It would seem at first thought that 
such a condition, occurring in an un- 
known corner of the Orient, was about 
as remotely connected with any prac- 
tical interest in this country as the com- 
plexion of the Grand Lama. But the 
world is rapidly becoming a small place, 
and obscure facts of natural history in 
one remote section may become of pro- 
found significance on the other side of 
[' A remote part of northeastern 
8 
the globe, affecting property, health, 
and even life. The disease above re- 
ferred to is what we now know as the 
Chestnut Bark Disease, and iscaused by 
the fungus Endothia parasitica. This 
parasitic fungus appears to have been un- 
wittingly introduced into this country, 
probably in the 90’s or late 80's, and to 
have been distributed to various points 
in chestnut nursery stock. The para- 
site found the American sweet chestnut 
a wonderfully susceptible host, and has 
spread and assumed characters on this 
tree which, so far as we know, are wholly 
unparalleled in its native habitat. 
There were possibly many importations 
of this disease. Its early history in 
this country is obscure, and will prob- 
ably alwaysremainso. By 1903 or 1904 
it was in full blast in the vicinity of New 
York City, and its subsequent spread 
is authéntic history. There were other 
old centers, but the vicinity of New 
York City appears to be the oldest. 
ITS DISTRIBUTION 
The disease is now generally dis- 
tributed in native chestnuts from Merri- 
mack County, N. H., and Warren 
County, N. Y., on the north, to Albe- 
marle County, Va., on the south. In 
New York the western border of dis- 
tribution is sharply delimited by an 
area without chestnut trees—a natural 
“immune zone’’—which extends south- 
ward along the eastern borders of 
Fulton, Montgomery, and Schoharie 
Counties nearly to the Pennsylvania 
line in Delaware County. Consequently, 
in New York the range of the disease 
is at present practically limited to the 
valley of the Hudson. In Pennsylvania 
the western limit of general infection is 
roughly along a curved line extending 
