PATHOGENICITY OF THE CHESTNUT BARK DISEASE 1 

 Clarence F. Korstian '11. 



A conservative estimate of the value of the chestnut in 

 the State of Pennsylvania would aggregate no less than $60,- 

 000,000. With so large a capital involved, it can readily be seen 

 why the Commonwealth of Pennsylvania was one of the first 

 states to take up the campaign against the chestnut tree bark dis- 

 ease. Pennsylvania has already lost over $20,000,000 from this 

 disease. An Act was passed by the State Legislature in 1911 pro- 

 viding for an appropriation of $275,000 to be used for the investi- 

 gation and control of the chestnut bark disease in Pennsylvania. 

 The expenditure of this sum was controlled by the Pennsylvania 

 Chestnut Tree Blight Commission consisting of five citizens of 

 the State, who were appointed by the Governor and served with- 

 out salary. 



HISTORY AND DISTRIBUTION. 



In the latter part of the year 1904, Merkel (10)- reported 

 a peculiar form of disease attacking the American chestnut, 

 Castanea dentata, in the Bronx Zoological Park in New York 

 City. A study of the infection was then undertaken and pure 

 cultures of a fungus were successfully isolated by Murrill (12), 

 who later described this fungus as Diaporthe parasitica. Because 

 of its formation of ascospores within well-defined perithecia it 

 rightfully belonged among the Pyrenomycetes. The question of 

 its nomenclature will be reserved for later discussion, since there 

 has been considerable difference of opinion concerning its proper 

 taxonomic position. Clinton (3 & 4) advanced the theory that 

 the fungus alone is not entirely responsible for this serious epi- 

 demic. He maintains that winter injury resulting from the severe 



iKevision of a thesis presented to the Faculty of the Graduate College, 

 University of Nebraska, in partial fulfillment of the requirements for the 

 degree of Master of Forestry, February, 1913. The major portion of the 

 data herein presented was collected while the writer served as Research 

 Assistant and Assistant Pathologist of the Pennsylvania Chestnut Tree 

 Blight Commission. Grateful acknowledgement is made to Dr. P. J. An- 

 derson and Mr. S. B. Detwiler for the many helpful suggestions and valu- 

 able criticism in connection with this work. 



2Bibliographic citations refer to "Literature Cited", p. 65. 



