39 CONNECTICUT EXPERIMENT STATION REPORT, 1912. 



healthy one. * * * Dry weather checks the disease by sup- 

 pressing spore production. * * * Winter injury is not common 

 over the whole range of the bark disease, but may be locally 

 important in producing lesions through which the parasite 

 enters. Winter injury bears no other relation to the bark 

 disease." Metcalf (35, p. 225) in 1912 said again: "No definite 

 evidence, experimental or otherwise, has been adduced to show 

 that a tree with reduced vitality is more susceptible to infec- 

 tion, or that the disease spreads more rapidly in such a tree 

 than in a perfectly healthy and well nourished tree of either 

 seedling or coppice growth, provided that such reduced vitality 

 does not result in or is not accompanied by bark injury by 

 which spores may gain entrance." 



Now, if the condition of the host bears no relation to the 

 rise and spread of the disease, the writer knows of no satis- 

 factory explanation for its sudden and destructive appearance 

 in this country except its importation from some foreign 

 country. The evidence to date, however, is very strongly 

 against the idea that it is an imported pest, as we shall show 

 later. Among the farmers in Connecticut who have been able 

 to watch this disease rather closely there are many who believe 

 that the weakened vitality of the chestnuts has had considerable 

 to do with its development and spread in this state. The 

 writer more than anyone else has advocated this view, and we 

 propose to give here the reasons we have for holding it. 

 Briefly expressed, they are as follows: 



The chestnut blight was brought to sudden prominence just 

 after the severe winter of 1903-04, which injured and killed 

 fruit and forest trees in general along the coast and water- 

 courses, of which New York City was the central point. The 

 resulting enfeebled condition of the chestnut enabled the blight, 

 a previously inconspicuous parasite, to spring into sudden 

 prominence on these trees and to gain credit for the death of 

 others which had been largely or entirely due to winter injury. 

 Since then we have had one or two severe winters, and more 

 especially several dry summers, that have injured not only the 

 chestnut, but other forest trees over an extended area. Due 

 to its successful attack on the weakened trees, the blight fungus 

 has perhaps acquired an added virulence that has enabled it to 

 attack apparently healthy trees, especially those of sprout 



