ILLINOIS NATURAL HISTORY SURVEY 



CIRCULAR 53 



brown discoloration (Fig. 3, 4, and 5) described above. In dying and 

 dead trees invaded by bark beetles, the fungus grows in the galleries 

 made by the larvae or grubs of the beetles (Fig. 6). These galleries 

 are in the inner layers of bark with groovings on the outer surface of 

 the sap wood. 



Fig. 4. — The removal 

 of bark from branches 

 that wilt in early summer 

 usually reveals long, 

 broken, brown streaks on 

 the surface of the sap- 

 wood. 



Fig. 5. — Brown discoloration 

 of the outer surface of sapwood 

 on the trunks of wilting elms is 

 a common symptom of Dutch 

 elm disease. 



