330 MANUAL OF TREE DISEASES 



Symptoms. 



The general symptoms of this root- and butt-rot are as 

 follows. The mycelimn invades the heartwood, sapwood and 

 bark of the roots. The most rapid progress is made in the heart- 

 wood. The first sign of the rot is a bluish discoloration of the 

 wood. The wood then becomes dirty yellow and finally 

 brownish or red-brown. While this color change is progressing, 

 black spots appear in the spring-wood of the annual rings. 

 Rapid decomposition of the fibers around the black spots results 

 in white areas with black centers. The white areas then coalesce 

 and result in the complete destruction of the spring-wood. This 

 leaves the layers of brown and brittle summer-wood as separate 

 sheets of tissue. These sheets shrink and, falling apart, cause 

 the root to become more or less hollow. While this process of 

 destruction is going on in the wood, white sheets of mycelium 

 are formed in the bark, which is killed. The same general 

 changes are shown in the heartwood of the trunk where the 

 amount of resin present does not interfere with the development 

 of the mycelium. 



The sporophores of the causal fimgus are formed on the roots 

 and base of affected trees. They appear as perennial, shelving 

 bodies with a light brown upper surface and white or yellowish 

 imder surface. The inner structure of the bodies is. white. 

 Small pores are apparent on the under surface. The sporo- 

 phores are also often found under the siu-face of the soil as 

 incrusting bodies on the roots and base of the trunk. 



Cause. 



The brown root- and butt-rot of conifers is caused by Fames 

 annosus. The spores from the tubes on the under sides of the 

 fruiting-bodies may cause infection through wounds in exposed 

 roots or possibly in fire scars and other wounds at the base of 

 the tree. The most eflScient means of spreading from tree to 

 tree is by way of the roots which come in contact with each 



