218 MANUAL OF TREE DISEASES 



Yellow Root-Rot 



Caused by Sparassis radicata Weir 



In the Northwest the roots of larch are often destroyed by 

 this root-rot. Fir, spruce and pine are affected by the same 

 disease. The bark and sapwood of the roots are killed. Yel- 

 lowish fan-shaped plates of mycelium are found in the bark. 

 The medullary-rays and heartwood are also decayed and be- 

 come yellow or brown. The fruiting-bodies of the causal 

 fungus are peculiar. They are attached to the diseased roots 

 by long, fleshy stalks. New fruiting-bodies are formed each 

 year from the tip of the stalk. They are large, white, compact, 

 fleshy structures covered with curled and lacerated leaf-like 

 plates. These th in plates stand upright on the upper portion 

 of the fruiting-body or horizontally from the sides. The spores 

 of this fimgus are borne over the entire exposed surface of the 

 fruiting-body. For fiulher details concerning this root-rot, 

 see imder fir diseases, page 170. 



