Sudden Oak Death (SOD), also known as Ramorum leaf blight or Ramorum dieback, is a fungal disease of plants only recently discovered in Europe and the United States. It can cause two types of diseases: bleeding bark cankers that may kill the host plant, and twig or foliar blights that may not kill the host plant but may serve as a reservoir for the pathogen.
What causes SOD?
The causal agent or pathogen for SOD is Phytophthora ramorum. It was first identified in Germany and The Netherlands on ornamental rhododendrons in 1993. In June 2000 it was isolated from dying oak trees in California.
Where is it originally from?
The geographic origin of P. ramorum is unknown. The European and North American populations, however, are thought to be distinct populations moved independently from another location.
Where besides California has SOD been found in the United States?
Besides California, SOD has been confirmed in Oregon, Washington, and in at least 5 Florida and 5 Georgia nurseries. It has also been confirmed in British Columbia.
What plant species does SOD affect?
Presently, the host range for SOD is broad. To date, it has naturally infected and killed or injured at least 28 host species and has been recovered from an additional 30 plant species. Examples are various species of west coast oak, coast redwood, and Douglas fir, which are all susceptible to bark cankers. Examples of hosts susceptible to twig or foliar blight are species of Camellia, Rhododendron, Vaccinium, and Viburnum. Visit the following site for the most current and complete lists of regulated and associated hosts: www.aphis.usda.gov/ppq/ispm/sod
How does SOD spread?
SOD most likely spreads through infected plant material, rainwater, and soil. Moist, cool, windy conditions are thought to spread the pathogen by dispersing spores from the leaves of foliar hosts.
What are the symptoms of SOD?
On trees susceptible to the most virulent form of the disease, large, bleeding cankers form on the trunk or main stem accompanied by browning of leaves. Infected trees may die within several months to several years after initial infection. On leaves of other hosts, dark gray to brownish lesions with indistinct edges indicate infection. The lesions can occur anywhere on the leaf, in vascular tissue, or on the petiole. Some hosts with leaf lesions defoliate and eventually show twig dieback.
Has SOD been found in New Jersey?
No, at the time of this posting the disease has not been found in New Jersey.
Is there concern that SOD could spread to New Jersey?
Yes. Undetected infected nursery stock shipped from an area or nursery where SOD has been confirmed could spread the disease.
Has stock from infected nurseries been shipped into New Jersey?
Yes. Two large nurseries in California located outside of 12 quarantined counties tested positive for SOD in March 2004. In 2003 the two nurseries shipped a significant number of plants to retail nurseries, garden centers, and individual consumers in New Jersey. No shipments, however, have been made from either facility to New Jersey in 2004.
What is being done about shipments of plants susceptible to the disease?
On 9 April 2004, the USDA issued an order restricting the interstate movement of host plant material from the entire state of California. Those restrictions include requirements that nurseries be inspected and tested for the presence of P. ramorum before regulated nursery stock is moved out of state.
In New Jersey, the New Jersey Department of Agriculture (NJDA) and the USDA - Animal and Plant Health Inspection Service (APHIS) are tracing the movement of plants that may be infected with SOD. NJDA staff and APHIS officers have jointly visited the retail nurseries and garden centers that received the potentially infected shipments to stop the sale of any remaining nursery stock, and are working with Rutgers New Jersey Agricultural Experiment Station (NJAES) Cooperative Extension to test plants that had not yet been sold. The NJDA sent an advisory letter with a USDA - Forest Service color fact sheet on SOD to consumers who received plants directly from the Californian nurseries last year. The NJDA plans to send an advisory letter and a copy of the fact sheet to nurseries and garden centers throughout the state to alert them to the symptoms of SOD.