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Oak wilt
Ceratocystis fagacearum
Synonyms
 
None 

Plant hosts
 
All Quercus species. Red oaks are more susceptible than white oaks. The pathogen can also infect chestnuts (Castanea spp.), chinkapin (Castanopsis spp.), and tanoak (Lithocarpus densiflorus).

Symptoms
 
In red oaks, the disease is characterized by a very rapid wilting of infected trees. Red oaks wilt from the top of the crown down, usually within 2- to 4-weeks. Individual leaves wilt from the leaf tip and margins to the leaf base, turning bronze or brown in color. The fallen leaves often remain green at the base. In white oaks, the leaf discoloration appears similar to early autumn colors, rarely resembling the symptoms seen in red oak leaves. White oaks typically die one branch at a time, taking several years to succumb to the infection. In both red and white oaks, the fungus invades the sapwood of infected trees causing a browning of the vascular tissue.
 
Symptomatic red oak leaf Cross-section of symptomatic oak branch
Images from Dave French and Jenny Juzwik (U of MN)

Transmission
 
Tree to tree spread is accomplished primarily through root grafts between neighboring oak trees. The fungus also forms sporulating mats underneath the bark of killed red oaks. These mats exude an odor that attracts sap- and bark-feeding beetles. The beetles become contaminated with fungal spores while feeding on the mats. When the beetles leave the mats to feed on wounded oak trees, they carry the pathogen's spores to those wounds.

Geographic distribution
 
In the United States, from the Lake states to Texas, and over to the East Coast from Pennsylvania to South Carolina.  Oak wilt is also present in Canada.  The fungus has been reported in four European countries (Bulgaria, Poland, Romania, and Spain) although none of these reports have been officially confirmed. 

Applicable regulations
 
Oregon has a state quarantine (OAR 603-052-0120) in place to prevent the introduction of oak wilt.
 
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