Foamy bark canker—Geosmithia pallida
On coast live oak, pink to white frothy exudate on bark is caused by Geosmithia pallida. The fungus is spread by the western oak bark beetle, Pseudopityophthorus pubipennis.
Identification
Symptoms occurring on the trunk and primary branches include wet discoloration seeping through entry holes caused by the western oak bark beetle. Peeling back outer bark reveals brown, discolored phloem tissue and small beetle entry holes. At the initial area of attack, a reddish sap may ooze from the beetle entry hole, followed by a prolific foamy liquid, which may run as far as 2 feet down the trunk.
Life cycle
The fungal pathogen is transmitted from infected to non-infected oak trees during movement and feeding by adults of the western oak bark beetle. The fungal disease causes decline, branch dieback, and tree death.
Solutions
No control methods are known as of 2016. Be alert for new information on this problem.
If you suspect that you have found these symptoms of the foamy bark canker disease on coast live oak outside of areas where it is known to occur, please contact either your local UC Cooperative Extension office or county agricultural commissioner.
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Dieback on coast live oak
Foamy bark canker oozing liquid
Vascular tissue discolored by Geosmithia pallida
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