340 MANUAL OF TREE DISEASES 



Brown Checked Wood-Rot 



Caused by Polyporus sulphureus Fries 



The black walnut is at times affected by the brown checked 

 wood-rot caused by the sulfur fungus. Oak, chestnut, maple, 

 butternut, locust and alder are often affected by the same 

 disease. The wood is changed to a reddish charcoal-like sub- 

 stance which is split into cubes. These cubes are separated 

 from each other by sheets of mycelium. The sporophores of 

 the causal fungus are orange and sulfur-yellow and appear in 

 late summer. The symptoms are more fully described under 

 oak diseases, on page 247. 



