325 



The New York Apple Tree Canker 



By Lex R. Hesler 



(Abstnictt'd from :i thesis prrseiited in oomiietitiou for the Eastiuun Prizo 

 ill r.ioldgy, Wabash Cullege.) 



Much credit is due those who have aided in writing this paper ; to 

 I'rof. M. B. Thomas for valuable suggestions, to Prof. Donald Reddick and 

 I'rof. II. II. Whetzel for suggestions and pliotographs. 



THE HOST 



The economic importance of the apple tree makes the disease in ques- 

 tion well worth consider ation. That the apple as a"i agricultural product 

 has a vast relative value cannot be denied. We have only to turn to cer- 

 ti-in statistics to find fairly accurate figures regirdiiig the absolute dollar 

 \alue of a single crop. Gannett ('03)^ estimates that the annual crop is 

 worth above $175,000,(X)0. As an orchard product, the apple comprises 

 .".-% of orchard trees and produces S2% of the total bushels of orchard 

 fruit. 



THE DISEASE 



The term "canker" has come to be a general one, and is usually applied 

 lo any disease which causes the death of definite areas of bark on the 

 limbs and trunks of trees. Conseipiently some modifying term is necessary 

 in order to indicate which cnnker is under consideration. I'addock COO)- 

 first used the naiiia New Y(U-k apple tree canker, thus distinguishing it 

 fioin the European canker, Illinois blister canker, firo blight canker, and 

 ethers. 



The (lisi'tisc fre(Hiently occurs on twigs, where it is usually called "twig 

 Iilight." but this is confusing, since this term is applied to fire blight. 

 AVhen the disease occurs on leaves it is known as "frog eye." Black rot 

 refers to the disease as it appears on fruit. 



The earlier theories regarding canker lead us to believe that the dis- 

 eases under consideration probably were not the New York apple tree 



''03, Gannett, H. Twelfth Csnsus of the United Slates 1900: 74-78. 



"'99. Paddo:k, W. Th? Nsw York Apple Tree Canker. N. Y. (Geneva) Agr. Exp. Sta. Bull. 

 15}:180. 1899. 



