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ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



Smooth Patch. — Smooth patch, sometimes called smooth 

 bark or white patch, is a fungus disease of the outer bark of 

 white oak. It causes the outer rough bark to slough and leaves 

 irregular to circular, smooth, light gray, depressed areas in the 



Fig. 6.5 {top). — Dothiorella cankers on oak develop as oval to elongate, 

 dark brown, depressed areas in the bark of affected branches. A conspicuous 

 ridge is visible between the diseased bark on the top and the living bark on 

 the bottom of the section of branch in this picture. 



Fig. 66 ^center). — Fruiting bodies of the Dothiorella fungus develop 

 as pustules in the dead bark of oak and erupt through irregular openings in 

 the outer bark. 



Fig. 67 ibottom). — In an oak affected with Dothiorella canker, the sap- 

 wood beneath the diseased bark is discolored dark brown to black, and 

 streaks of discoloration extend into the adjacent living wood. 



