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 oj Plant Industry, U . S. 



Department of Agriculture, Washington, D. C. 



IN A remote part of northeastern 

 China, in the province of Chili, 

 east of the Great Chinese Wall, 

 and four or five days' journc}' by 

 bulloek 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 valle^^s and is also 

 cultivated by the Chinese for its nuts 

 (fig.l). 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 

 proljably 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- 

 s]jicious 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 j^rac- 

 tical interest in this country as the com- 

 ])lexion of the Grand Lama. Rut the 

 world is rajjidly l)ecoming a small place, 

 and obscure facts of natural history in 

 one remote section may become of pro- 

 found significance on the other side of 



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 is caused 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 coimtry is obscure, and will j^rob- 

 ably always remain so. By 1903 or 1904 

 it was in full blast in the vicinity of New 

 York City, and its subsequent spread 

 is authentic 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 ])ractically limited to the 

 \-alley of the Hudson. In Pennsylvania 

 the western limit of general infection is 

 roughly along a curved line extending 



