Other than for copper-based sprays, what control methods are available for cypress canker?

There are several  products that have been tested for controlling cypress canker. The following paper maybe the most useful one to compare products.
Della Rocca, G., Di Lonardo, V., Danti, R. 2011. Newly-assessed fungicides for the control of cypress canker caused by Seiridium cardinale. Phytopathologia Mediterranea. 50 (1), pp. 65-73.

The most effective active ingredients for preventive treatments appear to be Azoxystrobin and thiophanate-methyl.

A good approach to slow down the disease may consist of:

1) Cutting down infected trees to reduce the chance of contagion. If only a few tips are infected, prune branches rather than take down the entire tree.

2) Cut down all Leyland cypress as it is a major vector of the disease.

3) Treat remaining healthy trees with products containing azoxystrobin (an active ingredient less toxic than thiophanate-methyl).


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 There is also a YouTube video you can watch at 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 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.

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.

If the stump of a felled tree is left in place, can the roots to continue to grow?

A lot depends on when the tree is felled. If a tree is cut in winter, it is possible that the root system will experience an additional year of growth. What happens to the root system depends on many variables, including soil type and presence of other trees of the same species adjacent to the one being felled. If the same species is present and the root systems of neighboring trees are grafted, the roots may be kept alive by trees still standing.  Some species, like aspen, will actually sprout new shoots along the root system. Often a stump with roots that are alive will seal the cambium on the stump surface, resulting in a round bump along the entire circumference of the tree right over the cambial area (i.e. just inside the bark).



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.

Armillaria is slowly killing my Thuja hedge. What is a comparable replacement hedge that will give me the same amount of privacy and be resistant to this fungus?

The first question to ask is what type of irrigation is being used currently on the hedge. Most landscape oak root fungus problems are due to overwatering in summer months. However, Thuja orientalis (=Platycladus orientalis) is quite susceptible to Armillaria even without heavy irrigation as highly susceptible species do not require excessively high soil moisture to be killed.

Prior to any new planting, as much of the old hedge (including roots) should be removed. In addition, any other decaying wood should be removed. Replanting with plants that do not require supplemental watering is best. Some CA natives that make good hedges include: ceanothus, island mountain mahogany, manzanita, and toyon. Non-native possibilities include Leyland cypress and Japanese privet. Keep in mind though that even plant species listed as resistant to oak root fungus will die if overwatered.