16 MICHIGAN CIRCULAR BULLETIN NO. 135 
delay the rapid spread of the fungus. Such quarantine regulations have 
been very important means of slowing up the spread of the blight across the 
country. It is no doubt due to ‘these strict quarantine measures that the 
invasion of this state has been so -long after the initial outbreak of this 
fungous disease in the United States. 
Resistant Trees 
Since direct efforts for the control of the blight have failed, hope has 
been expressed by many chestnut owners regarding the development of 
immunity to the fungus by the native trees. The Office of Forest Pathology 
(4) and other agencies have made extensive searches for blight resistant 
plants throughout the entire range of the chestnut, and especially in the 
regions where the blight has been present for several years. Individual 
trees have exhibited some differences in their susceptibility but the results 
of these surveys show that the majority of trees which are seemingly blight- 
resistant have simply escaped infection. It has also been noted that the 
many sprouts which so frequently appear at the base of blight-killed trees 
are merely blight-escaping and do not indicate that the tree has developed 
a resistance to the fungus. As this new wood becomes infected and dies it 
is replaced by younger sprouts which in turn escape infection for a period. 
Although continued effort is being made to locate chestnuts which are 
immune, there is little evidence at hand which gives immediate promise 
of the native trees exhibiting even a relatively high degree of resistance. 
The European chestnut, Castanea sativa, also known as the French, 
Spanish, and Italian chestnut, is likewise susceptible to the chestnut blight. 
This chestnut is not, therefore, recommended to the growers for planting 
purposes in Michigan. A large number of Asiatic species and varieties, 
however, are less susceptible to the blight, not only in their native habitats 
but they have exhibited also such resistance in experimental plots and 
orchards in this country. Some of these trees have indicated a marked 
resistance to the blight. 
‘In view of these facts, the United States Department of Agriculture has 
collected thousands of nuts from such blight resistant trees in Korea and 
Japan.. The seedlings obtained from these nuts will be observed for their 
hardiness and their ability to resist the blight in various parts of the United 
States. Over 2,000 of these trees have been planted in the vicinity of 
Ann Arbor, Michigan and an additional number have been set out in south- 
western Michigan. (Plate VIII B.) 
Realizing the desirability of securing more immediate results, efforts have 
been made to graft scions from Asiatic trees on American stock. In spite 
of the fact that the scions from many foreign trees have shown resistance, 
the stocks have succumbed to the blight, resulting,,of course, in the death 
of the entire tree. Experiments in grafting scions from various foreign 
varieties in Asiatic stock are now in progress at Washington and in other 
localities in the United States. 
Attempts have been made also to hybridize American stock with native 
chinquapin and with various species and varieties of Asiatic stock. Although 
it is at present too early to predict the results of these experiments, it seems 
reasonable to assume that they should yield a highly resistant tree which 
will produce nuts equal in size and quality to the native chestnut. 
q 
