UCCE Orange County Master Gardeners
University of California
UCCE Orange County Master Gardeners

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New Pest in the Landscape causes Foamy Bark Canker

There is a new threat to our coast live oak trees.  A fungus associated with western oak bark beetle is causing the decline by spreading what is known as “foamy bark canker disease”.  This has been found in urban landscapes in Los Angeles, Orange, Riverside, Santa Barbara, Ventura and Monterey counties.

Find more information, including photos of trees with symptoms of the disease, at the Pests in the Urban Landscape blog and the Eskalen Lab website.

Symptoms occurring on the trunk and main branches include wet discoloration seeping through entry holes caused by the western oak bark beetle. Peeling back of the outer bark reveals dead tissue surrounding the entry hole, and multiple entry holes may be observed on each tree. Initially, a reddish sap may ooze from the entry hole, followed by a prolific foamy liquid, which may run as far as 2 feet down the trunk.

Currently, no control methods are in place to control the fungus or the beetle. When the infection is at an advanced stage, the coast live oak tree dies. 

If you suspect that you have found these symptoms of the foamy canker on your coast live oak tree, please contact either your local University of California Cooperative Extension farm advisor, pest control advisor, county Ag Commissioner office, or Dr. Akif Eskalen at UC Riverside. For more information visit www.eskalenlab.ucr.edu.

If you can’t find the answer on the site, don’t despair! We also have the capacity to personally assist you through our hotline.  Just contact us by email or by phone (voicemail) at 949 809-9760 and we will respond to your inquiry.
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