Agricultural experts on lookout for spread of plant disease

The fungus-like pathogen commonly known as Sudden Oak Death has already had a negative impact in the western United States. It was first reported in 1995 in central coastal California after it began killing thousands of tanoaks, coast live oaks and California black oaks. The disease also can infect a number of plants such as rhododendrons, camellias and viburnums.

The SOD pathogen was discovered last March in at least two California nurseries that ship plant material nationwide. The Tennessee Department of Agriculture banned imports of selected plants from California and halted all sales and movement of susceptible nursery products that could have already entered the state.

Teams of inspectors processed about 230 samples from 13 different sites at various nurseries, greenhouses and garden centers that received plants from California nurseries. Those tests last week revealed three positive cases of Sudden Oak Death at two Tennessee nurseries.

“This has been a massive undertaking,” said Anni Self, a plant pathologist with the state agriculture department. “We put a lot of man hours into checking these nurseries and plant dealers as quickly as possible.”

The infected plant material from the two nurseries in Tennessee will either be burned or double bagged and buried in a landfill, Self said. Exactly what will be done with the material will be determined by the U.S. Department of Agriculture, she said.

The situation with SOD should not deter the public from purchasing plants this spring, said state agriculture department spokesman Tom Womack.

“Whatever plant material was in question has been either tested and cleared or will be destroyed,” Womack said.

Sudden Oak Death, which is caused by a fungus-like organism, was first identified in 1993 in Germany and the Netherlands on ornamental rhododendrons. It was initially thought to be restricted to California and Oregon in the United States.

Florida, Georgia and Tennessee are among the southeastern states that could be prime candidates for the disease based on factors like climate and forest type.

The disease is most frequently found in camellia among nursery plants. Among oaks, northern pin oak and northern red oak are at least two eastern oak species that are highly susceptible to SOD.

Tennessee has at least 15 oak species that have commercial value, and oaks are included in about 85 percent of all forest types across the state. Their acorns are a major food source for a variety of wildlife.

George Hopper, professor and head of UT’s department of forestry, wildlife and fisheries, said oaks are the main component of Tennessee’s forests.

“Any threat to the oak species is a serious threat to Tennessee’s forest resources, both economically and ecologically,” Hopper said.

Sudden Oak Death is know to occur in the wild only in 12 coastal California counties. Federal and state scientists are about to expand a two-year-old survey to include high-risk areas across 23 states, including Tennessee.

Kurt Lamour, an assistant professor with the UT department of entomology and plant pathology, specializes in identifying the SOD pathogen through DNA samples.

Lamour is confident the interagency response team has surveyed all potentially infected plants that entered the state from California.

“I think in this scenario, based on a historical perspective with Dutch elm disease and the chestnut blight, they responded quickly and have the proper network set up,” Lamour said.

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On the Net:

Tennessee Department of Agriculture: http://www.tennessee.gov/agriculture/

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Information from: The Knoxville News Sentinel, http://www.knoxnews.com