SODmap Mobile App
After SOD Arrives in Your Area
Topic:
Once SOD infections have arrived, what can be done?
Recommendation:
- If SOD is present in a portion of the property remember to:
- Schedule all landscaping and construction operations to occur first in the SOD-free area.
- Ensure that equipment is cleaned after work in the SOD infested area.
- Minimize all activities and operations in the Spring. Fall is the best work to avoid spreading infection through disturbance. Pruning of large branches and stems in multi-stemmed oaks should occur possibly in late November, and never in February-June.
- If the property is downwind and down slope from a dense mixed forest with significant infestation, ensuring that water runoff is properly channeled may be beneficial to avoid spread of the disease by water.
- Oaks that have a buffer area of at least 10 yards (10m) around the main trunk, devoid of any bay laurels or rhododendrons, are less likely to become infected. Identify valuable oaks and clear a 10 yard area around them by removing all small and medium bays, or by pruning large bay laurel branches of large trees that may come into the “buffer”. Bay laurels need to be treated with systemic herbicides at least a couple of weeks before being cut down, to minimize re-sprouting. Avoid all overhead irrigation and summer irrigation near oaks. For oaks over 32″ in diameter (80cm), 50-65 ft (15-20m) may be appropriate.
- If oaks are not infected they can be protected with a single yearly treatment of phosphonate in November and early December. If treating in the Spring for the first time, repeat in the Fall and switch to a single yearly Fall treatment. Treatments are not a cure but will increase resistance in about three quarters of treated plants.
- Phosphonate treatments have no known damaging side-effects on the environment and their action enhances the natural defense mechanisms in the plant. If injecting the product, we recommend alternating with bark applications every other year, to minimize wounding.
- Ensure you or your tree-care specialist has attended a workshop on how to properly apply the product. Topical bark applications require:
- Topical bark applications require removal of thick moss and tarping of shrubs or other small plants nearby.
- Injections require knowledge of appropriate timing, number of injections per tree, and injection technique, injections should not be performed in the Spring.
- No chemical treatment of bay trees is known to be effective, and other alleged treatments of oaks have been shown to be ineffective in controlled experiments.
- Additional treatments such as carving or scribing the infection out of an oak, or amending the soil near oaks with a thin layer of compost are still untested and we cannot recommend them. In addition, wounds may be detrimental to the tree and facilitate further SOD infection. To minimize such risk do not attempt to remove lesions in the Spring when infection potential is high. Lesion removal from oaks is still completely untested and could have unknown side effects.
Research behind the Recommendation:
The arrival of SOD in an area may be very gradual over time or may occur in a single year. Knowledge of SOD biology and disease distribution may help you prepare for the arrival of SOD and may allow time to protect valuable trees. The SODmap Mobile app, available for iPhone and Android, is an invaluable tool for visualizing SOD infections on the ground, in real time.
Dead oaks represent a significant hazard to people and property and increased fire hazard, however oaks that are infected by SOD and are apparently green may be equally hazardous. In SOD-infested areas, monitor closely oaks and tanoaks that are near homes, access roads, paths, yards, and play areas, and remove trees that show significant SOD symptoms and may be hazardous due to their location. Dead standing oaks, whether still green or brown represent a serious hazard for homeowners and are documented to fuel hotter fires that can kill medium sized redwoods.
UC Berkeley researchers have surveyed a large number of Coast Live Oaks, Tanoaks, and California Bay Laurels and determined that significant natural resistance to SOD is absent or very rare. However all three species have individual plants that may be more tolerant than others. Currently resistant plants are not available on the market, but several oak species (Valley oaks Blue oaks, Oregon oaks) are not susceptible to SOD.
Links and References:
Before SOD Arrives in Your Area
Topic:
What to do before SOD arrives in your area.
Recommendation:
To help prevent the spread of SOD in ornamental plants you purchase, ensure that they come from a facility that is regularly tested for P. ramorum. Make sure that wood from trees in SOD-infected areas is not moved to uninfected locations. Ensure that shoes, vehicle tires, and tools are free of soil and organic debris that might harbor the disease.
Careful brushing tools or air-blowing all soil and organic matter from them is normally sufficient to eliminate the risk of contagion. If driving on dirt roads during the rainy season in highly infested areas, wash the vehicle before returning home or visiting SOD-free areas. Preventative application of phosphonate compounds may help slow the spread of the disease in uninfected trees.
Familiarize yourself with the distribution of SOD using our SOD Disease Distribution maps, SODmap Mobile app, or OakMapper, and learn to identify early symptoms on bay laurels and tanoaks. The California Oak Mortality Task Force is a comprehensive source for the latest information on SOD. Contact your county Department of Agriculture officer for testing and participate in the SOD Blitz Survey Project held each year from April to June.
Research behind the Recommendation:
P. ramorum is dispersed aerially usually at short distances 100 yards or less, but occasionally up to 1-2 miles. Movement of infected plants or plant parts, soil, and water may lead to new infestations. The current distribution of SOD is updated on our maps each year. Only a lab test can confirm SOD and early detection of SOD is best to maximize chances of slowing its spread.
Links and References:
PCR Testing for Sudden Oak Death
California Agriculture: SOD Treatments
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California Agriculture Vol 63, Jan-Mar 2009
Tracks of an Oak Killer
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About the Author
: Erin Loury
B.S. (biology) University of California, Davis
M.S. (marine science) California State University/Moss Landing Marine Laboratories
Internship: Los Angeles Times (Kaiser Family Foundation health reporting internship)
This story on sudden oak death was my final project for the graduate program in science communication at UC Santa Cruz. It was a wonderful opportunity to delve into a topic that I previously knew so little about. I was fascinated to learn about the waterborne disease organism, the role of bay laurels as carriers, and the ability to protect a tree with Agri-fos. I am very thankful to Matteo Garbelotto for making this story possible. Matteo’s willingness to talk at length about the disease was crucial in helping me develop my understanding. My eye-opening trip into the field to see sudden oak death up close also helped me frame the story. I greatly enjoyed attending a SOD Blitz to record material for the podcast that accompanies the story. Reporting and writing this feature has helped deepen my appreciation for the beauty, fragility, and importance of oak trees.
How to Test for SOD?
UCB SOD Treatment Training Workshops
SOD Blitz Project
SOD: Bay Laurel Removal
Topic: 
Selective removal and pruning of California bay laurel (Umbellularia californica) trees as a strategy to protect oaks and tanoaks from SOD infection.
Recommendation:
For oaks between 3″ (8cm) and 32″ (80cm) diameter at breast height (DBH), remove small and medium sized bay laurels for a distance of 30ft (10m) around the tree. If large bays are present it may be useful to prune large branches that fall within the 30ft (10m) buffer zone. For oaks larger then 32″ (80cm) DBH, increase the bay-free buffer zone to 50-65 ft (15-20m).
Bays are persistent landscape plants that re-sprout quickly and produce lateral tillers in abundance. As a result they are difficult to remove permanently. Useful techniques include adding a spreader to the herbicide or applying the herbicide with a “hack and squirt” technique (see links below). For best results, apply the herbicide when the tree is alive, wait approximately a month for the chemicals to be distributed throughout the tree, killing the roots, and then cut it down
Research behind the Recommendation:
Managing the presence of bays, the primary carrier of P. ramorum, around high-value oaks and tanoaks can reduce the number of infectious spores in the environment. However, bays are important species in their own right and care must be taken not to disrupt their role in the environment, particularly along streams where they are particularly important.
