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Contents (this page):
Distribution

Signs and Symptoms
Control Measures

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Oak Wilt


leaf showing symptoms of oak wilt
bronzing of leaves




Distribution of Oak Wilt in the United States 

distribution of oak wilt in US




Symptoms and Signs of Oak Wilt


bronzing of leaves
wilting, chlorosis, and flagging

Symptoms of oak wilt include chlorosis, bronzing (necrosis) of leaves, flagging, 
wilting, premature leaf fall and death. 



aerial photo showing patch of dead trees
Circular areas or patches of dead trees are characteristic of oak wilt as seen in these aerial photographs.
aerial photo showing dead trees



 
Typical leaf symptoms. This leaf and others like it would have been shed from the tree. 



 
vascular discoloration
vascular discoloration is limited to outer sapwood

Vascular discoloration is typical of trees with oak wilt. Note that the discoloration is
limited to the outer sapwood region. 



notice crack in bark side-view of pressure pad

Bark on diseased oaks may be cracked open by a structure produced by the fungus 
called a pressure pad. To the right is a side-view of a pressure pad.


pressure pad notice mycelium surrounding pressure pad reproductive phase of fungus is formed here

Pressure pads:  Note the mycelial mat surrounding the pads. It is here and on the pad that 
the reproductive phase of the fungus is formed. 



sapfeeding beetles feeding in area of pressure pad
One means of dissemination of Ceratocystis fagacearum is by insects. Here two sapfeeding beetles (nididulids) are feeding in the area of a pressure pad. Spores (conidia and ascospores) of the fungus are sticky and easily adhere to the body of the insect. 


note whitish mass of sticky ascospores

Perithecia of Ceratocystis fagacearum. Note the whitish masses of sticky ascospores. 



Cultures of Ceratocystis fagacearum isolated from diseased trees. The fungus produces mycelium that is distinctive in color and odor. 
cultures of Ceratocystis fagacearum


oak wilt can spread through root grafts

Another means of spread of this fungus is through root grafts. 




Control of Oak Wilt


eliminating root grafts is one control

A means of control of oak wilt is to eliminate root grafts between diseased and healthy trees. 
This may be done mechanically as shown by these slides.  Removal of susceptible oak species 
within 50 feet of a diseased tree is practiced in many states.  Stumps of cut trees are treated with a herbicide to prevent sprouting.  Pruning and forest activities that could result in wounding during 
spring or summer should be avoided. 
 

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This website was prepared by Becky Bernard.
Last updated on 04 February 2008 by M.J. Munster