166 MANUAL OF TREE DISEASES 



colored zone app^rs as if varnished. The under surface is 

 yellowish brown and covered with minute pores. 



Caiise. 



The red-brown sapwood-rot of conifers is caused by the 

 fungus Fomes pinicola. Infection occurs in wounds which ex- 

 pose the sapwood of the tree. The wood fibers are not de- 

 stroyed completely but are reduced to weak thin-walled struc- 

 tures with numerous cracks and fissures. The life history and 

 control of wood-rotting fungi is more fully discussed on page 64. 



References 



Schrenk, Hermann von. Polyporus pinicola (Swartz) Fr. In Some 



diseases of New England conifers. U. S. Dept. Agr. Div. Veg. 



Phys. and Path. Bui. 25 : 24^31, pis. 3-5, fig. 2. 1900. 

 Atkinson, G. F. Polyporus pinicola. In Studies of some shade tree 



and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. Bui. 



193 : 222-227, flgs. 80-81. 1901. 

 Hedgcock, G. G. Notes on some diseases of trees in our national 



forests. IV. Phytopathology 4: 181-188. 1914. 



Stringy Red-Brown Heartwood-Rot 

 Caused by Echinodontium tinctorium EUis and Everhart 



The destructive stringy red-brown heartwood-rot of fir, 

 spruce and western hemlock is a common disease of these trees 

 in western United States. White, Alpine, grand, noble and 

 Douglas fir, Engelmann spruce and western hemlock are known 

 to be affected by this wood-rot. The older stands of firs in the 

 northwestern forests are so badly damaged by this rot that 

 they are practically worthless. 



Symptoms. 



The first indication of this heartwood-rot is noticeable in the 

 branch stubs through which the fungus finds entrance to the 

 heartwood. The wood of the branch stubs is a rusty brown 



