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Foamy Bark Canker Disease

Western oak bark beetle carrying disease that is infecting, and killing, live oaks

Drought, injury and others stressors make trees susceptible to pests and diseases. Now, foamy bark canker disease is the newest discovered threat to coast live oak in California. The disease is carried by the native western oak bark beetle. It has been found in multiple counties in Southern California and threatens to destroy California's coast live oak trees.


  • Widespread: Found in Los Angeles, Orange, Riverside, Santa Barbara, Ventura and Monterey counties
  • Misdiagnosed or overlooked: Resembles bacterial wetwood, polyphagous shot hole borer (PSHB), fusarium dieback, and as a result may have been ignored thus far.
  • More serious than similarly named diseases: Not the same as non-fatal bacterial alcoholic flux (also called foamy canker). When infection is in an advanced stage, the coast live oak tree dies.


The telltale signs of many tree diseases and borer infestations are the same. Unfortunately, since symptoms are so similar, it can be difficult to make a proper diagnosis.

  • Bark necrosis (death)
  • Multiple beetle/borer exit holes
  • Peeling bark
  • Prolific, foamy seepage
  • Reddish- or cinnamon-colored sap


Proper and immediate diagnosis is key.

  • Continued plant health care
    • Mulch
    • Fertilizer
    • Water
    • Judicious pruning during dormancy
  • Pest suppression (there is no known fungus control method at this time)

If you're worried foamy bark canker disease is affecting your landscape, contact your local certified Davey arborist for an inspection or get more information on the pest.

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