42 FOREST TEEE DISEASES. 



ROOT FOMES. 



This fungus (Fomes annosus pronounced fomeez) 

 is considered in Europe one of the most dangerous 

 forest fungi, and is also destructive in the eastern 

 United States. Although at present apparently some- 

 what rare in California, it may prove to be more preva- 

 lent. It attacks almost all conifers of all ages and 

 some broadleaf trees. The infection starts in the roots 

 and spreads upward, destroying bark, cambium, and 

 sapwood and causing the sudden death of the tree. 

 The heartwood first appears streaky (bluish) and later 

 shows the very characteristic red rot, with small, elon- 

 gated, perpendicular white pits, often with a black cen- 

 ter (see Trametes pini}. Between the bark scales a very 

 fine mycelium appears. In resinous trees the rot is con- 

 fined to the butt, but in less resinous ones, such as firs, 

 it reaches far up the trunk. The disease spreads not 

 only by spores, but also from diseased roots to the sound 

 ones of neighboring trees. Whole groups of trees can 

 thus die within a very short time (see, however, Armil- 

 laria meUea). In this connection it should be remem- 

 bered that the sudden dying of groups of trees may 

 also be due to attacks by barkbeetles. 1 The perennial 

 fruiting bodies of the fungus are more or less crust 

 shaped, and porous, and usually grow on the roots, but 

 sometimes on the collar of the tree, though generally 

 below the surface of the soil. They are tan colored, 

 with a white underside and margin. 



1 See publications of the Bureau of Entomology. 



