LOCUST DISEASES 221 



in a smooth roll. The pores on the under surface are barely 

 visible. 



Cause. 



The yellow wood-rot of locust is caused by the fungus Formes 

 rimosus. It is similar in appearance to Fomes igniarius except 

 when it is broken open the older layers of tubes do not show 

 the white filling. The spores from the tubes on the under 

 surface of the sporophore infect the locust at branch stubs or 

 through the tunnels made by the locust borer. The mycelium, 

 after destroying the central portion of the heartwood, reaches 

 out along the medullary-rays and initiates the bands of decay. 

 The yellow wood-rot fungus is not known to continue growing 

 in dead wood and timber made from affected wood is said to 

 last as long as sound timber. For further details concerning 

 the life history and control of wood-rotting fungi, see page 64. 



References 



Sohrenk, Hermann von. A disease of the black locust (Robinia 



pseudaoacia L.). Missouri Bot. Gard. Ann. Rept. 12:21-31, 



pis. 1-3. 1901. 

 Schrenk, Hermann von, and Spaulding, P. Black locust disease 



caused by Fomes rimosus. In Diseases of deciduous forest trees. 



U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 45-46. 1909. 



Brown Checked Wood-Rot 



Caused by Polyporus sulphureus Fries 



The heartwood and sapwood of locust is often reduced to a 

 red powdery mass by the sulfur fungus. Oak, chestnut, walnut, 

 butternut, maple and alder are the other principal kinds of 

 trees commonly affected by the same rot. The sapwood and 

 bark may be invaded and the tops of the trees or large limbs 

 are thus killed. The sulfur-yellow and orange-colored fruiting- 

 bodies of the causal fungus are produced in late summer from 

 wounds or from the bark where the mycelium has invaded the 



