Advice for the Home Gardener from the
Help Desk of the UC Master Gardener Program
of Contra Costa County
Gardener's Request: We just moved into a 30-year-old house in the East Bay hills, and we expect to stay here a long time. We have numerous oaks and Bay trees on the property. We've heard from neighbors that we should get those trees reviewed by a trained arborist familiar with Sudden Oak Death (SOD), e.g. identification, disposal, and potential danger to other trees in your neighborhood. Can you please recommend sources?
MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your questions about your oak tree and how to identify sudden oak death (SOD). The links below include information on identification, disposal, and potential danger to other trees in your neighborhood.
Accurate disease diagnosis can be difficult because the symptoms caused by SOD (Phytophthora ramorum) are very similar to those caused by other fungi, insects, or adverse environmental conditions. The only way to confirm a P. ramorum infection is to take a sample and analyze the affected plant tissue in a certified laboratory. Several of the links include guidance on laboratories.
External symptoms of SOD canker development can include the bleeding of a thick, sticky sap. It oozes out of the bark, not from a crack or hole, typically smells like the inside of a wine barrel and is a deep burgundy but can vary in color from nearly black to an amber-orange. This brochure, A Homeowner's Guide to Sudden Oak Death, has a good image of the sap on a coast live oak:
California bay trees are the primary carrier of SOD fungus. You should see symptoms of infection on the leaves if they are infected. SOD shows as leaf spots and usually brown tips surrounded by a yellow halo: https://nature.berkeley.edu/garbelotto/downloads/sod_diagnostic_report_final.pdf
The recommendation is to remove bays within 30' of susceptible oaks. http://nature.berkeley.edu/garbelottowp/?p=1063.
Here are some local contacts with local links for more information and possible tests of your trees:
The SOD Blitz Project informs and educates the community about Sudden Oak Death, gets locals involved in detecting the disease, and produce detailed local maps of disease distribution. The map can then be used to identify those areas where the infestation may be mild enough to justify proactive management:
California Oak Mortality Task Force for information and how to find arborists they have trained to identify and sample for SOD infection:http://www.suddenoakdeath.org/
Contra Costa County
Department of Agriculture
2380 Bisso Lane
Concord, CA 94520
And, finally, here is the link to the UC Pest Note with even more detailed information about SOD:
Best of luck to you!
Help Desk of the UC Master Gardener Program of Contra Costa County (SLH)
Note: apologies... an earlier posted version required a minor editorial change for clarity.
Notes: Contra Costa MG's Help Desk is available almost year-round to answer your gardening questions. Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone: (925) 608-6683, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.edu/HortCoCo/ You can also subscribe to the Biog.