FIR DISEASES 165 



Red-Brown Sapwood-Rot 



Caused by Fames pinicola Fries 



The red-brown sapwood-rot is one of the most common dis- 

 eases of spruce, pine, fir, larch and hemlock, wherever these trees 

 grow. The fungus causing this wood-rot occurs less frequently 

 in living trees than it does on dead standing trees and logs. It 

 is thought that the fungus usually attacks living trees which 

 are badly wounded or in generally poor health. Vigorous 

 healthy trees are more rarely affected. The decay progresses 

 very rapidly and the wood is reduced to a light easily pulver- 

 ized mass. The wood of beech, birch, maple and other de- 

 ciduous trees is also destroyed by this fungus. 



Symptoms. 



In longitudinal section, the first evidence of the decay shows 

 as whitish spots or streaks irregularly placed. The white spots 

 have reddish brown centers. At this stage the wood is punky 

 and brittle. The spread of the mycelium from these centers 

 soon results in a uniform red-brown, easily pulverized mass of 

 loose fibers. The decayed wood shrinks in all directions, leav- 

 ing numerous cracks which are filled with white mycelial felts. 

 These felts are largely responsible for holding the decayed wood 

 from falling to pieces. 



The fruiting-bodies of the fungus are formed abundantly 

 and are the most conspicuous of the various shelf-fungi in 

 coniferous forests. When growing from wounds on living 

 trees, they are usually hoof-shaped. On logs and dead wood 

 they are broader and thinner. The upper surface is marked 

 by broad rounded concentric folds, each representing the re- 

 sult of a year's growth. From the center of the top to the 

 margin, the color varies from black to brown and reddish brown. , 

 The rounded margin is yellowish in the early summer and later 

 becomes reddish yellow or deep red. The surface of this bright 



