About Sudden Oak Death (SOD)
What is Sudden Oak Death (SOD)?
- SOD is a trunk disease caused by the pathogen Phytophthora ramorum (P. ramorum) that leads to the rapid death of oaks and tanoaks
- SOD has killed well over a million native trees in California and Oregon
- Infection and tree deaths are spreading in Woodside and Portola Valley
- The pathogen is manifested by two types of diseases:
1. SOD/Bark canker hosts - the oaks and tanoaks that are experiencing the dramatic deaths in our neighborhoods and forests
2. P. ramorum Blight/Foliar hosts - suffer from leaf spots and twig dieback, but effects are rarely fatal. However, often transmitters of the pathogen to susceptible oaks
3. Tanoak is only host susceptible to both SOD and P, ramorum blight; hence most susceptible to infection
Which trees and other plants can be infected by P. ramorum?
Many trees and plants can be infected by P. ramorum. Locally, trees of greatest concern are tanoak, coast live oak, California black oak, Shreve's oak, and California bay laurel.
How can I tell if my plants have it?
- Definitive diagnosis requires a lab analysis of symptomatic plant tissue
- Visual pre-screening can be done using symptomatic photos found at: http://nature.berkeley.edu/comtf/photos/plant_symptoms_thumbnails.html
- Most common symptoms:
Bleeding cankers on the oaks and tanoaks (thick sap on the surface with dark infected patches underneath)
Leaf spots on the bayOaks and tanoaks near bay are most susceptible to SOD
- Go to http://nature.berkeley.edu/comtf/html/disease_diagnosis.html to access a question key that can help you determine if you should have your plants sampled for P. ramorum
Is there a cure for SOD?
No, but a tree that gets infected will not necessarily die. Tanoaks are the most likely to die if infected.
How does SOD spread?
The spores of the pathogen can be carried by boots, tires, horses hooves, pets, and also be wind borne. They are transferred relatively easily during the wet season. Bay laurel is the driving force for P. ramorum spread in California's forests.
Is there anything I can do to prevent the spread of SOD on my property?
- Remove smaller understory bay trees, or trim the lower branches of larger bays, close to oaks or tanoaks
- Treat healthy trees that you want to protect from possible infection Agri-Fos mixed with PentraBark is the only registered preventive treatment
It will NOT cure a sick tree, just help prevent a healthy one from becoming infected
- Clean and disinfect all gardening tools used on infected plants
- Carefully inspect plants (especially camellia and rhododendron) at nurseries for symptoms before buying them
- Avoid planting high-risk nursery plants near oaks and tanoaks
Can I treat my trees myself or do I have to hire a professional?
- The decision to hire a professional or spray the trees yourself is up to you. As with any spraying activity, read and follow the instructions carefully. This includes both application procedures and timing.
- The California Oak Mortality Task Force (COMTF) has a list of tree care professionals that have been trained to apply Agri-Fos (www.suddenoakdeath.orq). If you choose to hire a firm, make sure the individual sent to do the spraying has been trained.
Is there anything else I should do to prevent the spread of SOD in our area?
- Avoid known infested areas during the rainy season and spring months.
- Before leaving an infested area, clean your tires, shoes, bike, pet's paws or hooves, and equipment to ensure all organic material has been removed.
What should I do with dead trees that have been killed by SOD?
- If you choose to remove a dead tree, it is important to dispose of it properly.
- Burning downed material is optimal.
- Use larger pieces for firewood.
- Season logs in sunny, dry locations, away from roads and oaks and tanoaks.
- Chip and spread smaller tree parts in thin layers in a sunny location to promote drying.
- Material taken off site must be transported in a sealed or tightly tarped vehicle and taken to a certified disposal center. Ox Mountain is the only disposal site in this area certified to accept SOD material.
Where can I get more information about SOD?
The COMTF has a great website where you will find most of the information available on P. ramorum and SOD, at www.suddenoakdeath.org
How are our tax dollars being used to combat SOD?
- San Mateo County Department of Agriculture and Weights and Measures will conduct site visits (on staff available basis) to sample potentially infested material for laboratory testing at a state approved laboratory (650 363-4700).
- Both Portola Valley and Woodside are implementing spraying programs for trees along Town roadways and properties.
- Midpeninsula Regional Open Space District is doing research on SOD in its parks and has implemented management activities to help slow pathogen spread.
You can also download this information in PDF format here.
Prepared by Woodside & Portola Valley Conservation Committees from COMTF material 7/2007