CHESTNUT DISEASES 141 



European and the Japanese chestnut and the western chin- 

 quapin (genus Castanopsis). Pure strains of the Japanese 

 varieties are resistant while all the other species are very sus- 

 ceptible. From an economic standpoint, the American chest- 

 nut is by far the most important species. 



The Endothia canker has also been known by the common 

 names, chestnut-blight and chestnut bark-disease. It was 

 first noticed in the New York Zoological Park in 1904. Since 

 that time it has spread for hundreds of miles, north, west and 

 south. It has proved to be the most destructive and rapidly 

 spreading tree disease known. The areas which have been 

 swept by the epiphytotic so far, are left apparently without a 

 single living chestnut tree; After many years of speculation as 

 to the past history of this disease, it was discovered in northern 

 China in 1913 and later in Japan. It is of slight importance in 

 its native home. There is little doubt now that the Japanese 

 chestnuts imported into this country brought with them this 

 unnoticed disease of the Orient. The increased destructiveness 

 of the disease in this country is due to the greater susceptibility 

 of the American chestnut. Many examples of epiphytotics due 

 to newly imported pathogenes are now a matter of record and 

 make the regulation of the interchange of plant products one 

 of the important phases of plant disease control. 



Symptoms. 



The tissues of the bark, including the cambium, are invaded 

 and killed. The dead areas of bark, or cankers, are especially 

 conspicuous on the younger limbs where the normal bark is 

 smooth and green. They may be seen at a distance because 

 of the reddish color of the dead bark in contrast to the healthy 

 green bark. Usually the cankered area is slightly sunken, 

 due to the killing and drying of the tissues. On young rapidly 

 growing coppice, however, swollen areas (hypertrophy cankers) 

 with the bark split open lengthwise are commonly found. Dur- 



