States ban California plants as fear of oak disease grows

SACRAMENTO -- Concern over a disease that has blighted coastal forests is prompting more states to close their borders to California-grown plants that could harbor a fungus-like microbe blamed for killing tens of thousands of oak trees.

The restrictions are being made at the height of the spring shipping season for California nurseries, which constitute a $3.3 billion industry. The state's growers export a fifth of their plants and expect to lose millions of dollars.

In the past month, four states -- Florida, Kentucky, Louisiana, and West Virginia -- have banned all live plants from California, after one California nursery discovered after it had shipped some diseased plants to nurseries in Florida and Georgia that some of its stock had been infected .

Georgia, Alabama, and Mississippi have banned California-grown camellias, rhododendrons, viburnums, and dozens of other plants known to host the tiny organism that causes sudden oak death syndrome.

Seven other states -- Arkansas, Delaware, Indiana, Minnesota, Montana, Tennessee, and Utah -- have also put up quarantines or have otherwise begun requiring certification that plants from California are pathogen-free. Canada has also put some restrictions in place.

''We've been fearing the arrival of this disease," said Denise Feiber spokeswoman for the Florida Department of Agriculture and Consumer Services.

''There are so many unknowns associated with this disease," Feiber said, ''that the threat and risk to Florida's $9.9 billion nursery industry is very substantial, let alone its risk to our natural environment."

California nurseries, backed by state officials, are pressing the US Department of Agriculture to draft guidelines that will standardize how states across the country handle the risks associated with the plant pathogen.

''We're working with the USDA and the other states to come up with a protocol. We need to find something more workable for nurseries," said Jay van Rein, a spokesman for the California Department of Food and Agriculture.

''What you're looking at is economic protectionism in those states like Florida," said Karen Suslow, cochairwoman of the nursery committee of the California Oak Mortality Task Force. ''It's a matter of getting to know the facts. They're kind of where we were two years ago when we didn't know a whole lot about the disease."

Biologists were puzzled when certain species of native oaks and tanoaks in California's Fog Belt, from Big Sur to the Oregon border, began dying a decade ago. It took researchers five years to identify the culprit: Phytophthora ramorum, a microorganism that produces trunk cankers that girdle trees to death.

Late last month, the US Department of Agriculture expanded statewide a quarantine that was already in place in 12 California counties for the past two years, most in the San Francisco Bay Area. As many as 1,500 nurseries must undergo inspection before they can resume out-of-state shipments of plants at risk of hosting the microbe.

The USDA has ordered a nationwide survey to determine whether the pathogen has spread beyond California and a small area in Oregon or whether it exists elsewhere in a benign form.

Of particular concern is the spread of the pathogen to red oaks and pin oaks in the Appalachians and the Midwest.

''We don't know how this pathogen will react in the eastern United States, and a lot of people don't want to take that chance of finding out," said David Rizzo, a plant pathologist at the University of California's Davis campus who helped identify the cause of the disease.

''But maybe the cat's already out of the bag," Rizzo said.

Not since the outbreak of Dutch elm disease in the late 1980s, which devastated North America's population of native elms, has there been such widespread concern about infestation. A century ago, a fungus began killing off the giant chestnut trees that were once common in the eastern United States and were, at the time, the largest hardwood trees in North America.

''It's happened before," said Steve Oak, a forest pathologist for the US Forest Service in Asheville, N.C. ''If it were to get a foothold here, it could do serious damage. Oaks are the most abundant hardwood genus in the east."

''We really don't know what could happen," he said. ''One possible outcome is that it will be totally benign in our environment. And at this point, none of us want to gamble that."

The pathogen's origins are still unknown. A similar strain appeared in Europe at about the same time as the oak die-offs in California. The European strain seems to afflict the same species of plants as that in California, but the plant mortality in Europe is highest among ornamental shrubs such as rhododendrons.

The California strain appears to be fatal only to certain trees, although dozens of shrubs and plants used for landscaping can carry -- and spread -- the disease.

Symptoms range from blotchy lesions on foliage to cankers on trunks and branches.

In March, inspectors discovered that some camellias at a Monrovia nursery in Southern California were infected, prompting nurseries in other states to inspect recent shipments.

It hasn't been good for business, said Richard VanLandingham, Monrovia's chief executive officer.

''It's having some impact. No doubt about it," VanLandingham said. Thus far, he said, the company has lost at least $1 million -- an amount that could double if out-of-state quarantines extend into the summer.

''We are doing everything we possibly can to cooperate," VanLandingham said. The nursery, among the state's largest, is in the process of destroying thousands of plants and is taking steps, he said, ''to make sure we don't create any additional problems."