Adapted from an article found on
Treatment and Management

November 13, 2003

How can I confirm that my oak tree has Sudden Oak Death?
Because other organisms and injuries can produce symptoms very similar to Sudden Oak Death on oaks, homeowners will not be able to diagnose their trees with absolute certainty. However, there are some steps that can help you determine if Sudden Oak Death is a likely possibility. Specific information that you will need can be found on the website or be obtained from offices of the University of California Cooperative Extension, County Agricultural Commissioner, or California Department of Forestry and Fire Protection (CDF). First, determine if your oak tree is a susceptible species. To date, trunk cankers have only been found on the following tree species: tanoak, coast live oak, Shreve oak, canyon live oak and black oak. Of these, tanoak is the species most likely to be killed. Second, determine if you are in an infested area. Check maps available on the website or contact staff in local Extension, Agricultural Commissioner, or CDF offices. If you are outside of an infested area, your tree could still have Sudden Oak Death, but it would be less likely. Third, compare the symptoms of Sudden Oak Death with those on your oak tree. Symptoms are described in brochures and on the website. Fourth, check other susceptible tree and shrub species nearby. Do they have symptoms of Sudden Oak Death? The probability that your tree has Sudden Oak Death will be greater if your tree is a susceptible species, exhibits typical symptoms of Sudden Oak Death, and is located in an infested area where other trees and plants are showing symptoms of Sudden Oak Death. Confirmation of Sudden Oak Death, however, can only be done through laboratory diagnosis. Diagnosis of Sudden Oak Death based on visual symptoms is a judgment rather than positive confirmation. If you ask a tree care professional to make such a judgment, determine what training or qualifications enable them to do this. A Special Note: if you live in a county that is not known to have Sudden Oak Death but you suspect that one of your trees has the disease, notify a local office of UC Cooperative Extension, the County Agricultural Commissioner, or CDF.

If my oak tree has Sudden Oak Death, what are the chances it will die?
There is no way to determine if an individual tree will live or die. Each tree responds differently to infection, and experience tells us that it is rare for a pathogen to kill all plants it infects. Depending on a number of factors, some trees may never become infected, some may become infected and survive for various lengths of time, and others may become infected and die quickly. Because Sudden Oak Death is a new disease in California, it will take time to determine just how likely these different outcomes are for different species of trees. Initial observations tell us that tanoak has a high probability of being killed by Sudden Oak Death, but some are still expected to survive. Live oaks appear to have a lower probability of being killed by Sudden Oak Death, but many live oaks are still killed by the disease. Sudden Oak Death appears to kill trees by girdling the main stem or trunk. Therefore, the number and severity of cankers on the trunk is an indication of how susceptible the tree is and whether it will die. A green tree may already be dead if cankers completely encircle the stem. Bark and ambrosia beetles will attack trees that are stressed, dying or recently dead, regardless of whether the trees have Sudden Oak Death. The presence of fine dust in bark crevices, ranging in color from off-white to reddish brown, is a sign of beetle attack. Fruiting bodies of the fungus Hypoxylon occur on portions of the stem that are already dead. If the fruiting bodies or dust completely encircle the lower stem of the tree, chances are good the tree is dead even if its foliage appears relatively healthy. It takes time for the foliage of a dead tree to dry out and turn brown. Hence, a dead tree could have green leaves and still look alive for a period of time.

Are there any treatments that will cure an infected oak tree or prevent infection in a healthy oak tree? Are there any activities that should be avoided to prevent Sudden Oak Death?
There are currently no known cures or preventatives for Sudden Oak Death.

Should an oak tree with Sudden Oak Death be removed?
A tree with Sudden Oak Death needs to be viewed and treated differently than a tree without the disease, but the disease alone is not justification for removing a tree. An important consideration with respect to any tree is whether or not it presents a hazard to life or property. All trees present some hazard, depending on the tree's structural integrity and its potential to do harm should it fail. Preliminary observations suggest that Sudden Oak Death increases the risk of tree failure by providing an opportunity for sapwood decay fungi to enter the tree. Since heartwood decay is common in many older trees, sound sapwood is essential to the tree's structural integrity. If both the sapwood and heartwood are decayed, tree failure may be imminent. The decision to remove a hazardous tree ultimately lies with the property owner. In order to get an object assessment of hazard, contact a certified arborist or other qualified professional. Any dead tree has an increased risk of failure.

Will removing a diseased oak tree prevent the disease from spreading to nearby healthy trees?
The threat of spread is generally not a valid reason for removing an oak tree with Sudden Oak Death. If an oak tree has Sudden Oak Death, it will likely be surrounded by many other trees and plants that harbor the pathogen. Hence, removing one or even a handful of infected trees will have little or no impact on local disease levels and spread. The only exception would be if local regulatory officials (County Agricultural Commissioner or Department of Forestry and Fire Protection) determined that an eradication effort was warranted. Eradication would only be considered under very limited conditions--if the disease were newly established in an area, the infestation was small, and the area was well removed from any other infestations of Sudden Oak Death.

If I have my infected oak tree cut down, what should be done with the wood?
Regulations currently prohibit the movement of infected wood, plants, and plant parts to areas that are disease-free. This includes all host species, not just oaks. Local spread of the pathogen occurs naturally, but long-distance spread occurs when people move infected host material. If you have infected trees cut down, make sure the wood and other tree parts are not transported to disease-free areas. Avoid leaving wood next to roads where it could be picked-up and transported off-site by unauthorized parties. The simplest and best way to deal with infected wood is to leave it on site, for example by chipping the wood and using it as ground mulch. Larger pieces of wood may be split for firewood for local use. Do not stack oak firewood next to living oak trees since this can lead to insect attack on the living trees. If this is not possible, consider seasoning the wood beneath a tightly sealed, clear plastic tarp to prevent the buildup of destructive insects.

California Department of Forestry and Fire Protection TREE NOTE #3, Controlling Bark Beetles in Wood Residue and Firewood, provides specific guidelines for firewood tarping. If infected wood is removed from your property, make sure it is utilized or disposed of in a way that does not spread the disease. Contact your local Department of Public Works or County Agricultural Commissioner's office for specific recommendations on handling and disposing of the wood. If the wood is being sold as part of a commercial timber harvest, contact the California Department of Forestry and Fire Protection. Tools and machinery that are used to prune, cut, or chip diseased trees should be cleaned and disinfected before use on uninfected trees or in uninfected areas. Some commonly used disinfectants include Lysol®, Physan20®, or a 10% solution of industrial bleach (1 part bleach in 9 parts water).


Santa Ynez Valley Tree Care
P.O. Box 1147, Santa Ynez, California 93460

(805) 688-5580

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