126 MANUAL OF TREE DISEASES 



sapwood of deciduous trees when they have been severely 

 injured. Otherwise the catalpa is the only tree in which this 

 fungus is known to cause a distinctive heartwood decay. 



Symptoms. 



The affected trees may be recognized by the holes in the 

 trunk where the old branch stubs have rotted. Insects and 

 birds remove the decayed wood and use the hollowed-out areas 

 in the trunk for habitations. In cross-sections of the trunk, 

 the first indications of the decay show as pale colored areas. 

 The spring-wood of the annual rings becomes reddish with small 

 whitish areas. Later both the spring- and summer-wood of 

 the annual rings are similarly affected. The decayed wood then 

 becomes straw-yellow and is very soft and brittle. The de- 

 cayed area enlarges rapidly and eventually the sapwood may 

 be invaded. The decay may extend into the branches and 

 roots. Coppice is usually affected if the wood of the stump is 

 decayed. 



The fruiting-bodies of the causal fungus are formed where 

 the bark is dead or on the affected wood when it is cut from 

 the tree. They are thin, tough shelving structiu-es, hairy on 

 top and marked with variable yellowish and brown shiny zones. 

 The imder surface is yellowish or white and covered with small 

 pores. The fruiting-structm-es are annual bodies but they 

 persist through the winter and may revive and shed spores in 

 the spring. 



Cause. 



The yellowish soft wood-rot of hardy catalpa is caused by 

 the fungus Polystictus versicolor. The spores from the tubes 

 on the under surface of the fruiting-bodies are wind-borne 

 and cause infection when they lodge in branch wounds. When 

 the trees are planted close together, the lower shaded branches 

 die and remain attached to the tree for some time. When 



