One phosphonate fungicide, Agri-Fos, is registered as a preventative treatment for P. ramorum for use on individual, high-value tanoak and oak trees. Treatment is not recommended in areas where infested plants are not already present.
Although there is no known cure, a preventative chemical treatment has shown promise in slowing spread of the pathogen. Ultimately, effective management of Sudden Oak Death requires early detection, quarantine, removal and destruction of infected plant material.
Application of phosphonate compounds has been shown to be an effective preventive treatment for sudden oak death (SOD), caused by Phytophthora ramorum, in coast live oak (Quercus agrifolia Née) and tanoak (Notholithocarpus densiflorus Manos, Cannon & S.H. Oh).
Phytophthora ramorum is a fungus-like organism that causes a disease commonly known as Sudden Oak Death (SOD). On the west coast of the United States it is a serious problem in California coastal oaks and bay laurel. It can also infect a broad range of nursery plants at which point it is referred to as Ramorum blight.
Sudden Oak Death may take up to two years to kill its host. Once a tree has died, it becomes habitat for a number of other organisms. Ambrosia beetles feed on the wood of dead trees. You may notice their characteristic white boring dust on the bark of trees that have been recently killed by Phytophthora ramorum.
The Pathogen
While most foliar hosts do not die from the disease, they do play a key role in the spread of P. ramorum, acting as breeding grounds for inoculum, which may then be spread through wind-driven rain, water, plant material, or human activity.
Oak wilt typically causes red oak leaves to turn brown around the edges while the veins remain green. Leaves are rapidly shed as the tree dies. Conversely, in live oak with the sudden oak death pathogen, the veins first turn yellow and eventually turn brown. Leaves are often retained on the tree after it dies.
Hosts, Symptoms, & Diagnosis
It can be lethal to tanoak, coast live oak, California black oak, Shreve oak, canyon live oak, and madrone saplings, while it may cause only a minor leaf or needle disease for other hosts such as California bay laurel, coast redwood, and Douglas-fir.
As with the red oaks, death can occur with a sudden browning of leaves throughout the entire crown, or more slowly with gradual leaf loss. P. ramorum infection in twigs can lead to shoot tip dieback or a shepherd's crook. Secondary organisms are likely to attack weakened and dying trees.
Since its discovery in California in 1994, Sudden Oak Death (SOD) has been responsible for the death of over one million oak and tanoak trees in California alone [7].
In yard settings where healthy oaks are extremely valuable to homeowners, and nearby oaks have oak wilt, homeowners may consider hiring an experienced, professional arborist to inject their healthy red or bur oaks with a fungicide containing propiconazole.
Phytophthora ramorum. Phytophthora ramorum is an invasive plant pathogen that causes sudden oak death, ramorum blight, ramorum dieback, and Phytophthora canker diseases. There is no cure for the diseases caused by P. ramorum.
Infected trees and their roots will usually die before root grafts can be re-established. The oak wilt fungus does not survive in the root systems of dead trees for more than a few years. The potential for spread of oak wilt through grafted roots is especially high after a diseased tree is removed or dies.
Herbicides. The easiest way to kill mature poison oak is to spray it with an herbicide. Use a product that contains either glyphosate (RoundUp, etc.) or triclopyr (Garlon, Ortho Brush-B-Gon, etc.)
If the leaves of your oak tree turn brown or black, this is a sign that the tree is dying. Other signs include a sudden decrease in the size of the leaves and a sudden change in the shape of the leaves. If you notice any of these signs, it is essential to contact a tree service company as soon as possible.
Once Sudden oak death infects oak trees, there is no known way to cure them. Therefore, most of the management practices discussed below are directed at preventing the spread of the disease to new plants or areas and protecting susceptible trees before they are infected.
Where does sudden oak death come from? SOD is caused by the fungus-like water mold Phytophthora ramorum, which was first recognized as a pathogen in 1995. Phytophthora ramorum can be spread over long distances through movement of infected plants or infested plant parts.
The following California counties have confirmed Phytophthora ramorum findings and are under State and federal quarantine: Alameda, Contra Costa, Humboldt, Trinity, Lake, Marin, Mendocino, Monterey, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz, Solano, and Sonoma.
Tree Injection With Systemic Fungicide: Trees within the buffer zone can be treated with a systemic fungicide (See Photo). Alamo is the product labeled for use in the control of oak wilt. It is applied by injecting the fungicide into the root flares. Alamo is most effective when applied as a preventive treatment.
Sudden Oak Death is a tree disease caused by the fungus-like plant pathogen Phytophthora ramorum.
If oak wilt infects one of the trees in the stand, the disease spreads through the common root system to adjacent trees and an oak wilt infection center begins.
It may be burned up or taken to an approved yard waste facility.