NAGS HEAD, N.C. -- Where picturesque oaks once stood, tens of thousands of ashen gray trees dot the hillsides along the northern California coast, victims of a disease called Sudden Oak Death.
An unsettling reminder of what could happen in the southern Appalachian forests if the organism that causes Sudden Oak Death is introduced into North Carolina's native and urban forests.
Although Sudden Oak Death (SOD) is a forest disease, the organism that causes this disease is capable of infecting a large number of woody ornamental plants that are commonly sold by nurseries and planted into urban landscapes.
Earlier this spring, the NC Department of Agriculture & Consumer Services confirmed that the fungus-like organism causing Sudden Oak Death, Phytophthora ramorum (pronounced Fi-TOFF-thor-ra ra-MOR-um), was introduced into the state in shipments of infested nursery stock from southern California.
Sixty-nine nursery and dealer locations in North Carolina received potentially infested nursery stock including camellias, and viburnums from a southern California nursery during the past year.
To date, camellias at nine North Carolina nurseries, dealers or garden centers have tested positive for SOD. Because approximately 6,000 plants sent to the 69 North Carolina nurseries were sold by the time the disease problem was discovered, we believe infected plants may have been planted into landscapes statewide during the past year. But to date, Sudden Oak Death disease has not been detected in any landscapes in North Carolina.
Plants were most likely sold in an easily recognizable green pot with Monrovia written in white lettering on the side. However, not all suspect plant material may have been sold in these containers.
The counties that had nurseries or garden centers that received potentially infected camellias or viburnums are located in Beaufort, Buncombe, Chatham, Clay, Cumberland, Davidson, Forsyth, Gaston, Guilford, Henderson, Hyde, Iredell, Jackson, Johnston, Lee, Lenoir, Lincoln, Macon, Mecklenburg, Moore, New Hanover, Orange, Pitt, Randolph, Rowan, Stanly, Surry, Union, and Wake counties.
Those who bought camellias or viburnums from January 2003 until March 2004 should inspect the plants for brown leaf spots or twig dieback symptoms. The microorganism is found only on the leaves or branch tips, and does not infect the roots.
In June 2004, SOD infected rhododendrons were discovered at a nursery in Columbia County, Oregon. Approximately 1,400 rhododendrons in 5 and 7 gallon containers were shipped from this Oregon nursery to Lowes Home Improvement Stores across North Carolina. Although the risk of these plants having SOD is low, some of these plants could be infected with SOD.
Homeowners and landscape professionals can submit leaf samples for SOD diagnosis thorough their local North Carolina Cooperative Extension office. The NCDA&CS will begin accepting suspect plant material for diagnosis beginning July 19.
- Collect no more than 20 leaves per plant. Do not collect healthy appearing leaves as these cannot be tested. Likewise avoid collecting completely dead leaves.
- Collect leaves with suspect leaf spots and place them in a plastic "ziplock" bag and
- Take them to your local Extension Center along with a submission form.
- Do not return any plants or leaf samples to the nursery or garden center where they were originally purchased.
- Do not move, dig, or destroy any plant that has already been planted in the landscape. Moving a plant could result in spreading the disease organism to other locations.
- Do not compost the plant or put it with yard clippings for curbside pickup as those materials may be mulched and spread back into the landscape. Fallen leaves should be collected, sealed in a plastic bag, and discarded with your household trash.
In addition, about 190 customers in North Carolina received bonsai camellias that could SOD-infected. These plants were shipped from a nursery distributor in San Diego County, California between March 2003 and March 2004.
Customers would have received these plants from one of six mail order retailers.
Customers receiving suspect plant material received letters from the US Department of Agriculture Animal and Plant Heath Inspection Service in April alerting them to this possibility. Customers received a second letter in June from the NCDA&CS inquiring about the plant's health and location. If you received a letter and have not responded, you are encouraged to do so.
Background:
Despite the name, Sudden Oak Death disease is not just restricted to oaks.
Camellias, rhododendrons, Pieris, mountain laurel, viburnum, and lilacs are among 60 different plant hosts or potential carriers of the disease.
Only above ground plant parts are affected. The roots of infected plants remain healthy.
On oaks, the organism causes bleeding cankers on the trunk that can eventually girdle and kill the tree. On the majority of host plants, however, the disease causes leaf spots and twig dieback, but very rarely results in plant death.
Infected oak and tan oak trees in California forests are typically found in close proximity to other host plants such as bay laurel that have infected leaves. As such, it would be unusual to have an infected oak tree with a bleeding canker without the presence of other nearby foliar plant hosts such as mountain laurel or camellias. The disease is not known to spread from oak to oak.
Symptoms:
Camellia. The appearance of the leaf spots can be quite variable on Camellia. Generally the leaf spots are light to dark brown in color, may appear to be greasy, and often start at the tip of leaf and progress down the middle of the leaf toward the point of attachment. As the disease progresses, concentric rings of dead tissue may be observed on the infected leaves. Infected camellias may also drop their leaves, leaving sparse or barren stems.
Viburnum. The disease on Viburnum is somewhat variable, but the leaf tips are often affected first, and the brown discoloration spreads toward the base of the leaf in a V-shaped pattern. Tissue may initially appear soft and wet, but will become dry with age. Small branch tips may also be killed, causing the foliage to wilt. (Note: hole punches in leaves were made to remove leaf disks for analysis for Phytophthora ramorum the cause of Sudden Oak Death.)
Rhododendron. On rhododendron, brown leaf spots with diffuse margins often start at the tip of the leaf and move toward the petiole along the midrib. The tips of the branches may also become infected and spread from the petioles to the leaves resulting in v-shaped lesions starting at the base of the leaf. Affected branch tips may turn brown and wilt.
