SPRUCE DISEASES 329 



CuBoiDAL Wood-Rot 



Caused by Polyporus borealis Fries 



This wood-rot occurs in spruce and hemlock. No definite 

 statements are found in literature concerning its importance and 

 distribution in this country. The first evidence of the decay 

 in the wood is the appearance of fine parallel strands of mycelium 

 which burrow holes in the radial and tangential direction. 

 Later these strands of mycelium become larger and appear as 

 white cords in the wood (Fig. 28, page 186). Finally the 

 mycelium disappears, leaving numerous empty channels, and 

 the wood splits into minute cubes. For further details con- 

 cerning this wood-rot, see under hemlock diseases, on page 185. 



Brown Root- and Btptt-Rot 



Caused by Fames annosus PVies 



Practically all conifers are occasionally affected by the brown 

 root- and butt-rot. In Europe this disease is recognized as 

 one of the most destructive to conifers in the forest. In this 

 country it is found to some extent both in the eastern and 

 western forests, but it is not nearly so important as many 

 other root and trunk diseases. It occasionally occurs in pine, 

 spruce and fir, and may be expected in other conifers, including 

 juniper. The fungus causing this root-rot is sometimes found 

 on deciduous trees, but is considered both in Europe and North 

 America to be of negligible importance and probably never 

 parasitic on hardwood trees. The characteristics of the rot 

 seem to differ somewhat with the kind of tree affected, but since 

 these variations have not been described it is impossible to treat 

 them in detail. In the conifers with a low resin-content, the 

 decay extends upward in the trunk for several feet. This is 

 especially true in the firs of the western forests. In resinous 

 conifers, the rot is confined to the roots and butt of the tree. 



