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ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



Woodrot. — Woodrot diseases, caused by fungi, produce 

 decay of the wood of trunks and large branches. Decay usually 

 develops slowly and may not noticeably shorten the life of an 

 affected tree. However, it causes serious losses in the produc- 

 tion of lumber and other wood products. Most wood-rotting 

 fungi produce fruiting bodies of the bracket type (Fig. 26) or 



Fig. 27. — Fruiting bodies of the mushroom-type, wood-rotting fungi 

 may develop on the trunks of trees or in litter around the bases of trees. 



the mushroom (toadstool) type (Fig. 27). Because these fungi 

 enter trees mainly through unprotected wounds, it is important 

 to treat wounds promptly to prevent infection. 



Vascular Diseases 



Most vascular diseases are caused by infectious agents 

 (fungi, bacteria, or viruses) which invade the tree and develop 

 in the sapwood or inner bark. These diseases may cause the 

 leaves on one or more branches to wilt and die or the entire tree 

 to die. Fungi and bacteria that cause wilt usually produce dis- 

 coloration of the young sapwood, especially that of the current 

 season wood. This discoloration, usually brown, may appear as 

 streaks or as diffused discoloration of individual wood rings. Two 



