San Jose Mercury News, March 11, 2004

The microbe that causes sudden oak death has been found in a large wholesale plant nursery in Los Angeles County, the farthest south that the pathogen has ever been identified.

While there is no evidence that the fungus has spread from Monrovia Nursery into the surrounding region, the size of the nursery -- and the nationwide scope of its business -- has scientists worried.

" The nursery does a lot of shipping, so there is great concern about potential spread" of the microbe, said Katie Palmieri of the Sudden Oak Mortality Task Force. The news was announced at a meeting of the task force in Rohnert Park, hosted by Sonoma State University.

" There is particular worry about shipments back East, and if sudden oak death could take hold there," said Palmieri. Disease experts are now inspecting specimens of plants sent from the popular and respected nursery, which produces 22 million plants each year.

Since being detected in 1995 in oak trees in Marin County, the highly contagious disease has killed tens of thousands of oak trees along the California coastline.

Twelve counties in central coastal California -- including Santa Clara, Santa Cruz, San Mateo and Monterey -- have been hardest hit.

To the far north, a nursery in Vancouver, B.C., also was found to have the disease.

At least 40 different plant species can act as hosts for the fungus, which is related to the organism that caused Ireland's devastating potato blight.

Although it does not kill most of the species, scientists say it is unprecedented to have a pathogen spread across so many native plant species so quickly.

No symptoms of its pathogen, called Phytophthora ramorumas, have yet been detected on the East Coast or in the Appalachians.

But it has turned up in forests in British Columbia and the Netherlands. Earlier this month, a strain of a disease was found in two formal gardens in England.

The disease was discovered on several varieties of camellia in the Los Angeles nursery after a "trace back" investigation from a nursery in Stanislaus County, where an infected plant was found, according to Palmieri.

All of the infected plants have been destroyed and nearby plants are quarantined and inspected regularly for symptoms, she said.

Tests of the surrounding environment did not find any traces of disease, suggesting it had not spread outside the nursery, Palmieri said.

Sudden oak death spreads through airborne or waterborne spores. Although many infected plants do not sicken, others die quickly. Symptoms include oozing cankers on the bark and canopies that quickly turn from green to brown. Treatment is available to help individual trees.