Phosphonate is only intended to be used on trees that do NOT have sudden oak death (SOD). Once a tree is infected, it is of no use. It helps to boost the tree’s own immunity system against the pathogen. So, if a tree is very susceptible to P. ramorum (the pathogen that causes SOD), then it may still get infected and die, even with the phosphonate treatment. Really, the phosphonate just helps increase the odds that a moderately susceptible tree will be able to ward off infection. So, it is an odds game and you are just increasing your odds of success. Variables that contribute to success include tree susceptibility, disease pressure in the area, hosts present in the area, and environmental conditions.
Research has identified coast live oak individuals that may be somewhat resistant to SOD, possibly because of the presence of some chemicals in the bark and phloem. However, there is no information yet on how genetics and the environment may affect this trait.
Tanoak has some mother trees that produce SOD-tolerant seedlings and some that produce seedlings that respond very well to phosphonate treatments. These tanoak families are at UC Berkeley, but are not currently commercially available.
Yes, you can apply phosphonate to your oak trees to help protect them from sudden oak death. You can find it in many Bay Area garden supply stores.
If you apply it topically to the bark, you will also need the surfactant Pentra-Bark® and you will need a sprayer. If you choose to inject it, you will need enough injectors to treat your largest tree (1 injector every 6 inches around the circumference). Treatments should be applied between November 1st and December 15th for best results.
For details on how to apply phosphonates, go to www.matteolab.org, “Treatment and Diagnosis” (at top of page).
My coast live oak trunk is oozing. I sprayed the bark in January. Can you estimate how long it will be before the tree fails and we have to remove it?
The symptoms on your oak may be caused by a range of issues. If oozing is accompanied by the presence of fine sawdust, then the tree is dying. Even if it is still green you may want to consider removing it if its failure may cause harm to people or property. The fine sawdust is caused by beetles tunneling in the tree. Oaks are only attacked by beetles when dying. If no sawdust is present, then the tree’s condition may be reversible.
Unfortunately, it is difficult to determine what may be the cause of the symptoms you describe. Sudden Oak Death (SOD) can attack an oak tree if California bay laurel is within 60 feet of the oak. You can use the free SODmap Mobile App to determine if you are in a high or moderate risk zone for SOD. To find out how to do that, go to www.sodmapmobile.org. There is also a YouTube video you can watch at https://youtu.be/zE0_q3EmIfs. If the information you gather suggests that it may be SOD, then repeat the phosphite bark application (such as Agri-Fos® combined with Pentra-Bark®) in the fall between October 30th and December 15th. You may also want to consider removal of bays within 30 feet from the oak. Go to http://nature.berkeley.edu/garbelottowp/?page_id=909 to find out about upcoming treatment training sessions to learn more about treatment options. If there are no bays within 60 feet of your oak and the SODmap mobile risk is low, then it likely isn’t SOD.
If you have watered your oak, it may be a root disease such as the oak root fungus or Phytophthora cinnamomi root disease. Make sure you stop watering and expose the upper root system to the air to slow disease progression. If you have never watered your oak, then it may be a secondary disease brought on by the long drought (ex. oak die-back fungus). These are diseases that are strongly affected by the genetics of the tree and weather conditions. In this case, you may want to try watering the tree now and then once again in 2 weeks. Then water once a month starting October 15th. Do not water between July 10th and October 15th. Watering should be done using a low flow approach to ensure that the soil gets wet up to 1 foot down and that no flooding of the tree ever occurs. Unfortunately, if the secondary disease is too advanced, despite all efforts, the tree may still die.
The revised SOD treatment recommendations can be found at: https://nature.berkeley.edu/garbelottowp/?p=1039.
I have an oak tree that is leaking a dark substance 4′ up the trunk, but otherwise it looks healthy. I live in Alameda County. Do I need to be worried about sudden oak death?
Download sod map mobile and tap the risk button. If the risk shows up as high or moderate, call an arborist listed at http://www.suddenoakdeath.org/diagnosis-and-management/arborists-applicators/. If you get an insufficient data response, then see if you have any CA bay laurel trees within 20 yards of the oak. If you find any, do they have possible P. ramorum (pathogen that causes sudden oak death) symptoms (symptomatic photos: http://www.suddenoakdeath.org/library/photos/plant-symptom-photos/; host information: http://www.suddenoakdeath.org/diagnosis-and-management/hosts-and-symptoms/). If you do find questionable symptoms on bay, again, call an arborist listed at http://www.suddenoakdeath.org/diagnosis-and-management/arborists-applicators/ for a site visit.
Can coast live oak be used in a large-scale Bay Area tree planting project without exacerbating SOD?
My organization is considering launching a large-scale urban tree planting project in the Bay Area, with the goal of adding one million trees to the urban forest inventory within 15 years. We are interested in coast live oak (CLO) as a major component of the effort for a number of reasons, including the ease with which seed can be collected and planted, drought tolerance, habitat value, high potential for carbon sequestration and rainfall interception, and status as a “signature tree” of the local landscape.
The plan is to gather seed locally from many locations, and plant with minimal site preparation and no supplemental irrigation or other artificial life support systems. Trees will be monitored and cared for over time, and replanting will take place as needed to ensure that we continue to make progress toward our goal. Obviously we don’t want to exacerbate the sudden oak death problem. Our hope is that, on the contrary, widespread and large-scale planting with subsequent monitoring might help identify resistant trees. What recommendations do you have?
First of all, this is a really neat project and you are absolutely correct about the benefits of planting CLO. Based on the information provided, the following are recommendations for the project:
In addition to coast live oak, it would also be good to plant Oregon white oak in the northern greater Bay Area, valley oak in the middle portion of the Bay Area, and blue oak in the southern part of the Bay Area. The rationale for this is that diversity/biodiversity is always good and the three alternate oak species are immune to SOD. A good overall planting ratio would be 75% CLO and 25% other species.
The big issue is going to be when California bay laurel is present, as it helps to spread Phytophthora ramorum. CLO should never be planted within 20-25 yards of bay for this reason. Unfortunately, bay has become invasive and SOD is actually increasing its abundance, so where bay is at least 10% of the stand, plant the other oak species recommended above. In riparian areas, bay should be left untouched.
We have old camellias and a pittosporum on our property that are healthy, but growing very close to coast live oaks. Should they be removed to help protect the oaks from SOD?
When thinking about P. ramorum dispersal, it is important to think about spread at two scales. First, the pathogen establishes itself on transmissive host leaves (e.g. California bay laurel, tanoak, redwood, rhododendron, and camellia) by moving up to several hundred meters during conducive rain events. Then, as the pathogen builds up, infection can spread from a transmissive host to an oak if it is within 20 m from the oak. If incidence of transmissive hosts is low in your area, chances are that an oak will not become infected even if a camellia or pittospsorum is a few meters away from it, so there is no need to remove these hosts if there are few bay laurels or tanoaks in your neighborhood. The second thing to keep in mind is that SOD is not everywhere. You can use SODmap mobile to help determine current levels of risk for oak infection on your property. If risk is low or negligible, again, there is no need to remove these plants, but they should be monitored for symptoms. The last thing to keep in mind is that the maximum distance between a transmissive host and an oak depends on the size of the transmissive host and on how infectious it may be (i.e. how well does it sporulate). For both camellia and pittosposrum, if the distance between your oak and plants is 10 m or more, they probably represent a low risk. If they are 7 m or less, they may represent a risk if your neighborhood has plenty of transmissive hosts.
If a homeowner suspects SOD is affecting their trees, there are a few options to get them tested. SOD kills several oak species and tanoaks, but it is primarily spread via infected California bay laurel leaves. Parties interested in testing for the presence of SOD can contact their local UC Farm Advisor or county Department of Agriculture to find out if they accept symptomatic bay laurel leaves for testing. (Go to Hosts and Symptoms on the California Oak Mortality Task Force [COMTF] website to learn what symptomatic bay leaves look like.)
Another option is to participate in a spring SOD Blitz. These are community-based, volunteer sampling efforts that are organized in cooperation with the Garbelotto lab. Training dates and locations are posted February 1st of each year for the upcoming sampling season at www.sodblitz.org. Training and sampling take just over an hour each and happen on the same scheduled weekend.
For infected oaks, call an arborist. A list of arborists that have attended a SOD training within the last 3 years is available on the Arborists and Applicators page of the COMTF website. NOTE: This list is only intended to be an additional filter for those looking for an arborist. It is not a list of recommended professionals.
We have bays 100 feet downwind from a coast live oak that seems to be dying of SOD. How do we have our oak tested and how do we determine if the bays are carriers?
Oak testing is routinely done by arborists. It is a rather involved and tedious process that requires a fair amount of finesse and know how as it entails wounding the tree by shaving off the outer layer of bark to collect infected tissue. If you decide to have your oaks tested for SOD, consider going to the Trained Professionals List for arborists that have recently attended an official SOD seminar (Not intended to be a list of recommended professionals, this list does serve as an additional filter when trying to identify arborists that are up-to-date on the latest science-based SOD information.).
Alternatively, a less invasive method of determining the presence or absence of SOD on your property is to sample symptomatic bay leaves (See Hosts and Symptoms for SOD symptoms.). Keep in mind that any infested bay in the general vicinity (typically within 200 ft of an infected oak) may be the inoculum source for infection of your coast live oak. If bay sampling is your preferred method for pathogen detection, you can call your local UC Cooperative Extension office to find out if the California Department of Food and Agriculture is processing leaves from your county and, if so, what the protocol is for sample submissions. In lieu of submitting samples through your county, you can go to www.sodblitz.org to find out when a SOD Blitz will be held in your region (Dates for each year are posted by January 30th. Blitzes typically occur from March to June). Attending a blitz will afford you the opportunity to learn more about SOD, including the latest disease control strategies, during a 1-hour training session. At the end of the session you will be given all sampling materials and instructions for submissions. Blitz participants are free to submit as many leaves as necessary, meaning that you can send in all suspicious leaves from your property as well as from the neighborhood or nearby local parks. All leaves are processed at UC Berkeley and all sampling results are published in a database available at www.sodmap.org or through the free App SODmap mobile.