OAK DISEASES 247 



will apply (see page 351). Care must be taken to remove the 

 affected wood beneath the cankered area or the mycelium may 

 spread into the healthy bark. 



References 



Heald, F. D., and Studhalter, R. A. The Strumella disease of oak 



and chestnut trees. Pennsylvania Dept. Forestry Bui. 10 : 1-16, 



pis. 1-12. 1914. 

 Buokhout, W. A. The undesirabiUty of red and black oak because of 



fungus disease. Pennsylvania Agr. Exp. Sta. Ann. Rept. 1899 : 



250-252. 1900. 



Beown Checked Wood-Rot 



Caused by Polyporus svlphureus Fries 



This important wood-rot is commonly found throughout the 

 United States in oak, chestnut, maple, walnut, butternut, lo- 

 cust and alder. It has also been reported, in white spruce in 

 Maine. In Europe this disease is important in certain conifer 

 as well as deciduous trees. Although not as destructive in the 

 forests of the Northeast as some other diseases, it is the most 

 common wood-rot of shade and ornamental oaks. The sap- 

 wood and bark are affected and the tops of trees and large 

 limbs are killed when thus girdled. The causal •fungus lives 

 saprophytically in all kinds of timber. 



Symptoms. 



The characters of the decay caused by the sulfur fungus 

 serve readily to identify it, even in the absence of the yellow 

 sporophores. The heartwood is usually first to be decayed. 

 Gradually, however, the sapwood and bark are invaded and 

 the living cells of these tissues are killed. The more com- 

 pletely decayed wood is often bordered by a wide slightly dis-- 

 colored zone. The decayed wood becomes reddish brown and 

 has the appearance of charcoal except in color. It is easily re- 

 duced to powder by a blow. In the process of shrinkage which 



