76 MANUAL OF FRUIT DISEASES 



mental trees are often filled with cement or asphaltum blocks. 

 Whether or not this practice is to be followed in the apple or- 

 chard depends upon the extent of the injury and the exposure 

 of the orchard to wind. As a general rule the filling of cavities 

 with any substance is not within the province of the practical 

 orchardist ; the operation does not pay. But in any case the 

 interior surface of the cavity should be coated with a wound- 

 dressing. 



REFERENCES 



Schrenk, H. von, and Spaulding, P. Diseases of deciduous forest trees. 



White heart-rot caused by Fomes igniarius. U. S. Agr. Dept. 



PL Ind. Bur. Bui. 149 : 25-37. 1909. 

 Atkinson, G. F. Studies of some shade tree and timber destroying 



fungi. Polyporus igniarius. Cornell Univ. Agr. Exp. Sta. Bui. 



193 : 239-247. 1901. 

 Hartig, R. Die Zersetsungserseheinungen des Holzes. Polyporus 



igniarius Fr., pp. 114-123. 1878. 



BLISTER-CANKER 



Caused by Nummularia discreta Tul. 



This disease, which is known as blister-canker, and Illinois 

 canker, was first given attention in Illinois in 1902. Since 

 that time it has been reported from the following states : 

 Arkansas, Indiana, Iowa, Kansas, Missouri, Ohio, Oklahoma, 

 Nebraska, New Hampshire, New York, Virginia and West 

 Virginia. Besides its occurrence in the United States, the blister- 

 canker is found in Germany, Italy and Cuba, although it does not 

 appear to have assumed great importance in these countries. 



In certain states, as, for example, Missouri, and the southern 

 portions of Illinois, Indiana and Ohio, this is the most injurious 

 canker disease of the apple. It is said that within the last few 

 years orchardists in Kansas, Missouri, Oklahoma and Nebraska 

 have lost more than a million trees from it. The injury con- 



