32( 



The New York Apple Tree Canker 



By Lex K. IIesleb 



(Abstracted from a tlu'sis pi'tseiited iu competition for the Eastman Prizo 

 in IJioloiry, Wabasli College.) 



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

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

 I'rof. 11. II. Whetzel for suggestions and i)hoto.gi'aphs. 



THE HOST 



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

 tion well worth consideration. That the apple as a:i agricultural product 

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

 tain statistics to find fairly accurate figures regarding the absolute dollar 

 value of a single crop. Gannett ("03)' estimates that the annual crop is 

 worth above $175,000,000. As an orchard product, the apple comprises 

 05% of orchard trees and produces 82% of the total bushels of orchard 

 fruit. 



THE DISEASE 



The term "canker" has c(tnK' 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. Consequently some modifying term is necessary 

 in order to indicate which canker is under C(insideration. Paddock ('l)O)- 

 first used the name New York apple tree canker, thus distinguishing it 

 from the European canker, Illinois blister canker, fire blight canker, and 

 ethers. 



The disease fre<iuently occurs ou twigs, where it is usually called "twig 

 blight," 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 ou 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. Twelfch Census of the Uuited States 1900: 74-78. 



' '99. Paddock, W. Thj Now York Apple Tree Canker. N. Y. (Geneva) Agr. Exp. Sta. Bull. 

 153:180. 1899. 



