ASCOMYCETES 281 



XLVIII. BARK DISEASE OF CHESTNUT 

 Diaporthe parasitica Murrill 



METCALF, HAVEN. The Immunity of the Japanese Chestnut to the Bark 

 Disease. Bur. Plant Ind., U. S. Dept. Agl. Built. 121 : 55-56. 1908. 



MURRILL, W. A. A Serious Chestnut Disease. Jour. N. Y. Bot. Garden 7 : 

 143-153. figs. 13-19. 1906. (Also 7: 203-211. Jigs. 25 -jo. 1906.) 



MURRILL, W. A. A New Chestnut Disease. Torreya 6 : 186-189. fig. 2. 

 1906. 



Occurrence. This bark disease of the chestnut has recently 

 been reported from New York, New England, and other north- 

 eastern states, and it would appear that it is spreading rapidly. 

 It is in fact becoming a serious menace to forest tree culture in 

 that section of the country. The common species of chestnut 

 (Castanea dentatd), seems to be in all localities peculiarly sus- 

 ceptible, and so far as the observations go, all species of the 

 genus Castanea are subject to it with one exception, this excep- 

 tion being certain Japanese varieties of Castanea crenata Sieb. 

 and Zucc. Metcalf has found the latter to be quite generally 

 immune, and while the nuts are inferior in flavor to the best 

 European varieties, it is nevertheless an important commercial 

 product. It is hoped that hybridization between the Japanese and 

 American or European forms will be successful in establishing 

 immune varieties with other desirable characteristics of the better 

 sorts. It is not believed, however, that the Japanese chestnut 

 can to any extent replace the native tree for forest purposes, 

 although the former is desirable from an ornamental standpoint. 

 It is suggested that since the Japanese chestnut was first intro- 

 duced on Long Island, it is possible that Japan may be the home 

 of this fungous pest, and that as a result no resistance could have 

 been developed in the native species. 



The fungus. The fungus has been found upon twigs, small- 

 sized branches, and trunks. It completely encircles the affected 

 limbs, and the girdling thus brought about ultimately causes the 

 death of portions beyond, and lessened vitality of the whole tree. 



The mycelium of the fungus is confined very largely to the 

 bark and to the underlying cambium. The affected cortex be- 

 comes somewhat light brown in color and slightly sunken after 

 desiccation. 



