Sudden Oak Disease Ravages Southern California, May Move East

PORTLAND -- Dying oak trees in the San Francisco Bay area were the first sign of a disease now considered a threat to a $13 billion U.S. nursery industry, the largest in the world.

"They looked around and all of a sudden there were dead oaks all over the hillsides," said Bob Linderman, the chief of a U.S. Department of Agriculture research lab at Oregon State University. "That's how it got its name."

Sudden oak death disease first appeared in ornamental shrubs in Europe in 1993 and within two years had begun killing trees in California. It later infected a commercial nursery in Southern California that shipped plants and shrubs around the country without suspecting the potential risk.

Last month, Agriculture Secretary Ann Veneman announced her agency would spend $15.5 million this year to help halt the spread of Phytophthora ramorum, the scientific name for the fungus that causes sudden oak death.

It can kill oak trees and seriously damage a broad range of other trees and shrubs, including rhododendron, camellia, big leaf maple and Douglas fir. The fungus is related to the plant disease that causes potato blight and triggered famine in 19th century Ireland.

The federal Animal and Plant Health Inspection Service, or APHIS, recently launched a national survey to assess the extent of sudden oak disease which threatens both nursery crops and wild forests.

The fungus already has been reported in 15 states where California nursery crops were shipped. At least 10 states have banned shipments from California, officials say.

The regions considered at high risk are the West Coast and the central South. In California, whole stands of coastal oak have been wiped out in some of the 13 counties listed as infected. The section of the Appalachians that stretches through northern Alabama and Georgia through Tennessee, North Carolina and Virginia also is an area of concern, although the disease has not been detected in the wild there.

"Florida is also a high-risk state because of its location, demographics and the volume of plant shipments passing through there," said Nolan Lemon, an APHIS spokesman based in Raleigh, N.C. He noted that nearly 80 percent of all the fresh-cut flowers imported into the United States pass through the APHIS inspection station in Miami.

The sudden oak death fungus spread through infected camellia plants shipped from nurseries in Los Angeles and San Diego counties in Califorina. The most current records show a total of 102 nurseries in 15 states received the infected plants, most of them from the Monrovia nursery in Asuza, Calif., which has destroyed infected stock worth millions of dollars.

The infection came as a surprise to the industry and regulatory agencies because the fungus generally spreads through water and cannot survive the hot, arid climate of Southern California, said Katie Bloome, Monrovia spokeswoman.

"They forgot the power of shade cloth and sprinkler irrigation," said Everett Hansen, a botany professor at Oregon State University who specializes in forest pathology.

The California Oak Mortality Task Force, a consortium of scientific and government experts, has been formed to track the disease, and Oregon State is serving as a clearinghouse for other states to coordinate their efforts.

The origin of the fungus remains a mystery. It may have come from Asia, and could also have spread by wind in addition to water.

"We don't know where it came from, and when we don't know, there's lots of room for speculation," Hansen said.