Thursday, March 11, 2004 (SF Chronicle)
Nursery reports oak disease
Infested plants have been sold out of state -- scientists shocked
Peter Fimrite, Chronicle Staff Writer
Ornamental plants in the largest nursery in California -- a place that
distributes flora around the country -- have been infested with spores from
the tree-killing disease known as sudden oak death, it was revealed
The discovery of Phytophthora ramorum in camellias at Monrovia Growers in
Azusa (Los Angeles County) means that the highly contagious disease has been transported to other states and may have been introduced into highly
susceptible oak forests in places like the southeastern United States.
The news hit like an earthquake as forest pathologists from around the
world gathered Wednesday at Sonoma State University for a California Oak
Mortality Task Force meeting.
Steve Oak, a forest pathologist for the North Carolina office of the U.S. Forest Service, said a great many of Monrovia's plants are shipped to the southeast, including places near the southern Appalachian Mountains, where Northern red oak trees make up 80 percent of the forest canopy in some places.
"We have a pathway that was theoretical before, but now is likely," he said during a break in Wednesday's conference. "The threat is very real."
It is especially troubling in that region because the oaks have replaced
the forests of American chestnut trees killed in one of the worst blights in world history. The chestnut blight, first discovered in 1904, killed some 3.5 billion trees in 50 years, essentially wiping out the entire species.
"It's a huge nursery with thousands of plants that went all over the
place," said Susan Frankel, a U.S. Forest Service plant pathologist who is
working with the state Department of Food and Agriculture on the problem.
"Hundreds of nurseries are now going to require inspections. Hundreds of
thousands of plants will have to be destroyed. We're very concerned for the
forests of the United States, for the nursery industry and trade. It's
The news of yet another infestation was a major setback after two years
of progress fighting the fungus-like scourge that has killed tens of
thousands of California's majestic oaks. The widening swath of destruction
seemed to have slowed in the past two years, especially in the Bay Area, and
an effective phosphite treatment was developed and approved for use on
But there were signs of trouble last year when Phytophthora ramorum,
which is the scientific name for the disease, was discovered in camellias in
a small nursery in Washington.
It meant the disease had spread to another state -- but infestations had
been found before in nurseries and isolated, so it wasn't yet a disaster.
However, Frankel said, the camellias were eventually traced back to
Monrovia. Testing of plants there confirmed Monday that six varieties of
camellias were infected, the first such infestation in arid Southern
The major concern is that the 500-acre nursery does $30 million annually
in out-of-state shipments, Frankel said, and many of the plants sent out
over the past year may have been infected. That means they may serve as
hosts and spread the disease to wildland areas.
Steve Lyle, spokesman for the California Department of Food and
Agriculture, said lab samples are being taken and analyzed to determine how
extensive the Monrovia infestation is. "Surveying is ongoing at other
nurseries in California as well to see if the fungus has spread even
further," Lyle said. Katie Bloome, the spokeswoman for Monrovia Growers,
said shipments of all plants that are susceptible to sudden oak death have
been halted and she is confident the problem can be eradicated. "We're
on top of it," she said.
Meanwhile, forest pathologists from the United Kingdom and the
Netherlands outlined during the conference how Phytophthora ramorum has
spread from nursery plants to forested areas. It seems to be especially
deadly for beech and red oak trees in Europe.
Curiously, the microbe in Europe -- which was recently also found in the
Pacific Northwest -- is a different mating type from the one that dominates
in the United States. Scientists are desperately trying to keep the two
types apart for fear that they will mate and create an even more virulent
form of sudden oak death.