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ILLINOrS NATURAL HISTORY SURVEY CIRCULAR 46 



Fig. 68. — Red, black, and other oaks in the red oak group, when affected 

 by oak wilt, usually wilt and die over a period of several weeks or during 

 a single growing season. In most cases, wilt of leaves appears first on 

 branches in the upper portion of the crown of the affected tree. The wilt 

 progresses downward and inward until all the foliage is affected. The tree 

 in the center of this picture has many branches without leaves, and leaves 

 on the remaining branches are wilted and dead. Located in Ingersoll Park 

 at Rockford, this tree was the first oak in Illinois from which the oak wilt 

 fungus was obtained. The tree, which died in 1942, showed brown streaking 

 in the current-season wood typical of the oak wilt disease. 



