Bleeding Oak Tree


While visiting a project site in Marin County with our favorite arborist’s Ray Moritz and Janel Yoshimoto this morning, we came across some oak trees with symptoms of Sudden Oak Death (SOD). We noticed a spot on the bark that appeared to be “bleeding” with a thick sap which is a common symptom of SOD. Sudden Oak Death has been killing native oak trees along Northern and Central California’s coastal communities since 1995. The disease is caused by a pathogen called Phytophthora ramorum and there are two host for the pathogen: bark canker host and foliar hosts. Diseased oaks and other tress are often attacked by other organisms that end up killing the tree and we found out today that it would only take about 48 little bugs to kill a beautiful heritage oak tree. I guess it takes one bug to penetrate through about 3″ of girth of the tree and when more and more bugs begin to penetrate the tree then it see’s the white light at the end of the tunnel and begins it’s slow descent into tree afterlife. Amazing how tiny little critters can take the life of an old and massive tree. Not all trees will die and the rate can vary from tree to tree depending on the health and severity of the problem that persists. There are about 40 other plant species that can be affected by SOD such as rhododendron, laurels and a variety of other species so look beyond your oaks for symptoms of “bleeding” and leaf spots.

More information about Sudden Oak Death can be found at:



~ by seamstudio on February 15, 2008.

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