Sudden Oak Death Found in South Carolina

CLEMSON, S.C. – Clemson University department of plant industry officials reports the first confirmed identification of the pathogen that causes Sudden Oak Death, Phytophthora ramorum, in South Carolina this year. Other positive plants have been found in Florida, Georgia, Louisiana and Tennessee.

"One of the major concerns about Phytophthora ramorum in the Southeast is that it is a forest pathogen in northern California, which is an area with a climate similar to the southern Appalachian Mountains," said Christel Harden, assistant department head for plant industry, a section of Clemson University regulatory and public service programs that oversees agriculture activities for the state.

According to federal guidelines, all plants in the block where infected plants are detected and all susceptible host plants adjacent to the block must be destroyed. In addition, a 10-meter buffer area should be established around the destruction zone, and any host or associated plants must be quarantined for 90 days, monitored and retested if necessary.

Clemson University scientists have been monitoring nurseries, landscapes and forests of South Carolina for P. ramorum, a fungus-like organism. The pathogen has killed thousands of oaks and associated plant species in the coastal forests of California and southwest Oregon and attacked ornamental plants (causing a disease called Ramorum Blight) in nurseries and landscapes in the United States and Europe.

"It's not been a question of if the disease would come south, it's when it would arrive," said Steve Jeffers, associate professor of plant pathology and leader of the Clemson Public Service and Agriculture's monitoring effort. "P. ramorum likely would cause the deaths of many trees throughout the Smoky Mountain region."

Sudden Oak Death was first observed in the United States in 1995 in California's Marin and Santa Cruz counties on tanoak trees. It since has spread through 14 coastal northern California counties and one adjacent Oregon county.

"The pathogen first was discovered in Germany and the Netherlands on ornamental plants and has now turned up in at least 14 countries, including England, France, Germany, Italy and the U.S.," said Jeffers.

Southeastern researchers worry that the disease could have the same effect on Eastern forests as chestnut blight did in the early 1900s. Caused by a fungus from Asia, chestnut blight nearly wiped out the species within 50 years.

If the pathogen takes hold in the South, P. ramorum could cause significant damage to the region's forest and nursery industries. In South Carolina, forestry is an $835 million industry. Hardwoods cover more than half of the state's 12 million acres of forests. The "green" industry – turf and ornamental crops – is South Carolina's No. 2 agricultural commodity, valued at $290 million.

A primary concern is that Phytophthora ramorum easily spreads by moving and handling nursery plants, as well as forest shrubs and trees, that are hosts for the disease. Many Southern plants rank high on the list of hosts: camellias, rhododendrons, azaleas, mountain laurels, viburnums and pieris, to name a few.

The symptoms of the disease look like many common plant diseases: leaf spot, tip burn, dieback, leaf lesions and bleeding cankers. Symptoms vary greatly from plant species to plant species.

"Don't dig up any plants or destroy them until plants can be tested," said Jeffers. "Plants put out for waste pick-up may be shredded for mulch and will end up right back in the landscape. Likewise, diseased plants tossed on a backyard compost pile or left lying around can be a source of infection for surrounding plants."

Home gardeners and landscape contracotrs should monitor host plants in landscape settings, particularly camellias planted in the last two years, for symptoms of Sudden Oak Death. Report any sick shrubs mentioned above to the Clemson University department of plant industry at 864/646-2139 as soon as possible, so the plants can be tested.