Plant Industry - Plant Protection Section
Sudden Oak Death (SOD)
Ramorum Leaf Blight, Ramorum Dieback
- a nursery plant disease that threatens oaks -
Sudden Oak Death (SOD), ramorum leaf blight and ramorum dieback are all names for a recently-discovered plant disease caused by the fungus-like microorganism Phytophthora ramorum. It has killed thousands of oak trees in California and Oregon in the past decade. More information is provided at the following website: USDA-APHIS-PPQ Phytophthora ramorum/Sudden Oak Death, the California Oak Mortality Task Force (COMTF), and the North Central IPM Center and PRED Program.
Although some eastern-U.S. oak species are highly-susceptible to SOD, the disease is not known to be established in landscapes, natural areas, or forests in States other than California and Oregon (as of 1/1/13). However, since 2004, it has been detected on ornamental nursery plants in many States, primarily in connection with infected plants moving in the nursery trade from the west coast. The known host range of is very broad and includes commonly-grown ornamental plants like camellia, viburnum, pieris, rhododendron, and many others. Although SOD does not usually kill these non-tree hosts, it causes symptoms such as leaf-spots, defoliation, twig and branch dieback, or blighting that can easily be confused with symptoms caused by other plant diseases or environmental stresses. Infected plants can easily escape detection. Laboratory analyses are necessary to confirm the presence of SOD in all cases.
NCDA&CS is concerned about the possible introduction of SOD into North Carolina on ornamental plants. Nurseries and nursery dealers often buy-in ornamental plants from other States where Pram is known to occur. Despite the federal quarantine requirements intended ot prevent the movement of the disease into other parts of the U.S. on infected plants, the measures are not 100% effective. Infected plants could still be shipped into NC, purchased by a homeowner or landscaper, and planted in the landscape where the disease could become established. From there, it could move into the larger environment and adversely impact our oaks and other trees. This is why NCDA&CS continues to survey and monitor plants in nurseries and nursery dealers on a routine basis for symptoms of SOD.
Activities in North Carolina
The first detection of SOD in a nursery in NC occurred in 2004. The NCDA&CS received a federal “trace-forward” notification that thousands of plants possibly infected with SOD were shipped over the previous year from an infested nursery in southern California to more than 1,200 locations in 39 states. Seventy of these locations were in North Carolina. NCDA&CS personnel inspected all of these locations, and SOD was eventually found in nine of them -- but only on plants shipped directly from the infested nursery. Those plants were destroyed. Based on subsequent surveys conducted by NCDA&CS and NC Forest Service personnel, SOD did not spread within the nurseries onto other plants nor become established in the surrounding natural areas surrounding the nurseries.
In the three-year period from 2004 to 2006, NCDA&CS personnel surveyed a total of 319 nursery and nursery dealer locations as part of a USDA-APHIS-PPQ-funded national survey. They also conducted numerous “trace-forward” investigations. Summary maps show the extent of the effort in North Carolina during this time period. Except for the 2004 locations already mentioned, there were no additioal detections. The NC Forest Service also conducted surveys in natural and forested areas and these were also nagative.
From 2007 to 2010, NCDA&CS continued its participation in the national survey of nursery and nursery dealers (250 locations total) and handled additional “trace-forward” investigations. The disease was detected at one NC nursery dealer in 2008 and there again in subsequent years despite eradication efforts and the application of other federally-mandated protocols. Monitoring and other regulatory activities are continuing at that location.. In 2009, SOD was found at another nursery dealer location, but it was not re-confirmed after the initial regulatory activities were completed. In 2011 and 2012, surveys continued in conjunction with the general nursery inspection program. There were no new detections.