744 



CHESTNUT 



CHESTNUT 



to protect against damage of the sprouts by fire on such 

 land. Clean cultivation, at least during the first few 

 years, is probably best in planted orchards, although 

 heavy mulching may be found a satisfactory substitute. 

 The Japanese and some of the American varieties of 

 the European species require thinning of the burs on 

 young trees to avoid over-bearing, with its consequent 

 injury to the vitality of the tree. 



Special difficulties. 



Leaf diseases are apparently subject to control by 

 bordeaux mixture, but for the weevils, which damage 

 the nuts previous to maturity, no satisfactory remedy 

 has yet been discovered except the yarding of poultry 

 in sufficient numbers to destroy the adult insects and 

 their larvae when they reach the ground. 



The most serious difficulty confronting the present 

 or prospective chestnut-grower in North America is 

 the chestnut-bark disease which, during the last decade, 

 has worked havoc in the native chestnut forests 

 throughout a region of country extending from cen- 

 tral Connecticut through southeastern New York, 

 New Jersey, and eastern Pennsylvania into northern 

 Delaware, northeastern Maryland and northern Vir- 

 ginia. As this region contains most of the commercial 

 plantings of improved chestnuts they have also suf- 

 fered severely, especially since about 1908. The distri- 

 bution of the native chestnut, together with the known 

 distribution of the disease February 1, 1912, is shown 

 on the accompanying map (Fig. 915), which was pre- 

 pared by Metcalf to accompany a special report on the 

 disease in response to a resolution of the United States 

 Senate. 



This disease, caused by a parasitic fungus (Diaporthe 

 or Endothia parasitica), attacks trees of all ages and 

 kills by girdling at various points. It is known to 

 attack all species of chestnut and chinquapin grown in 

 this country, although some, at least, of the Japanese 

 varieties, are practically resistant, so far as observed. 

 A few cases of the disease have also been found on 

 living trees of the chestnut oak in Pennsylvania, though 

 with less evidence of destructive effect than on chestnut. 



The disease is spread by the spores of the fungus, 

 which are sticky, and are carried by rain, insects, and 

 man, and probably by birds and small mammals. It 

 is known to have been carried on nursery stock for 

 long distances and is easily transported on newly cut 



914. Chestnut sprouts two years grafted. The cion was 

 inserted where branching begins. 



915. Distribution of the chestnut blight. 



timber and cordwood from which the bark has not 

 been removed. Infection frequently occurs through 

 wounds made by bark- borers. 



Although first attracting attention in New York 

 City in 1904, it appears certain that it had secured 

 a firm foothold in southeastern New York, including 

 Long Island and adjacent portions of Connecticut 

 and New Jersey, prior to that time, there being some 

 indication that it was introduced from Japan, although 

 satisfactory evidence of this is still lacking. The pres- 

 ence of the disease in chestnut forests in China was 

 discovered by Meyer in 1913, where, upon an unidenti- 

 fied species of chestnut, it is reported to be less virulent 

 than in American chestnut forests. 



For several years after publication of the cause of 

 the disease by Murrill, in 1906, little effort was made in 

 a systematic way to accomplish its control until 1911. 

 when the legislature of Pennsylvania appropriated 

 $275,000 for this purpose and inaugurated a state-wide, 

 two-year campaign of eradication. The work is being 

 done in cooperation with the Federal Department of 

 Agriculture which, since 1907, has been investigating 

 the disease with a view to developing effective methods 

 of controlling it. Several other chestnut-producing 

 states are also giving more or less attention to the prob- 

 lem. Up to the present time, systematic cutting out 

 of infected trees coupled with destruction of their bark 

 by fire has proved the only practicable control method. 

 This is being vigorously applied in Pennsylvania and 

 those portions of Maryland, West Virginia, and Vir- 

 ginia in which the disease has appeared. 



In forests, the disease is exceedingly difficult to 

 eradicate after it has once gained a foothold, owing to 

 the minute examination of the entire tree which is 

 required to locate infections in their early stages. In 

 any district in which there is a general infection of the 

 forests, the only practicable course is to clear off the 

 timber while it is sufficiently sound to be merchantable. 



The relative disease-resistance of the Japanese 

 chestnuts, coupled with their precocity and produc- 

 tiveness, renders them now the most promising sorts 

 for the American chestnut-grower. Planted in sections 



