Oak-killing disease found on a tree in New York state
Case on East Coast
raises new questions
Peter Fimrite, Chronicle Staff Writer
of a red oak tree in New York state infected with the killer disease
known as sudden oak death could force changes in a nationwide
quarantine of California nurseries as scientists re-evaluate the
spread of the mysterious microbe.
tree was found earlier this month inside the Tiffany Creek Preserve,
a 192-acre nature park in Nassau County, nowhere near any nurseries
that might have received diseased flora from California.
experts are at a loss to explain how the pathogen got to the
preserve or how long it has been there. The fungus-like organism,
known scientifically as Phytophthora ramorum, has more than 60 host
plants in the United States, but has, until now, never been found in
the wild outside of the coastal regions of Northern California and
what it means at the moment," said Kerry Britton, forest pathologist
for the U.S. Forest Service, in Washington, D.C. "The whole thing
seems very weird."
survey of the Nassau County preserve, including DNA samples from
every suspicious tree within a 20-acre section of forest, is being
conducted to determine if the infestation is more widespread,
according to Claude Knighten, spokesman for the U.S. Department of
Agriculture's Animal and Plant Health Inspection Service.
It's too early
to tell how big of a problem it is, Knighten said. "We're examining
and surveying the area as we speak," he said. "We've collected
several samples throughout the entire preserve and submitted those
samples to our lab. Once we get those results we'll decide what if
any action we'll take."
death has killed tens of thousands of oaks in the so-called "zone of
infestation," the 13 counties in California and in southern Oregon
where its presence has been confirmed.
quarantine of California nursery plants was started after the
discovery in March that Monrovia Growers, California's largest
nursery, was infested with the tree-killing disease. Some 600,000
plants in that nursery alone had to be destroyed, and the California
nursery industry estimates it has lost $50 million in revenue.
The disease has
also been found in nurseries and in nearby wildland areas in Europe.
The New York
oak tree's lack of any apparent connection to California is
particularly troubling to regulators and puzzling to scientists.
It could mean
that Phytophthora ramorum is a naturally occurring pathogen that
already exists throughout the country and, possibly, throughout the
world, according to some arborists and forestry experts. If that is
the case, then there is no reason for California nurseries to face
"The finding in
New York raises more questions about the distribution of P. ramorum
throughout the United States," said Don Dillon Jr., chairman of the
board of the California Association of Nurseries and Garden Centers.
"If it has been there for some time, it raises questions about the
whole nature of the pathogen. It may be naturally occurring in other
places. It could have come from back east and spread here."
County oak tree may be one of many infected trees on the east coast,
according to Ralph Zingaro, an arborist and the owner of Bioscape
Inc., a San Francisco organic pest management company. Zingaro is
the one who actually made the initial find after being hired by the
California Association of Nursery Growers and Garden Centers to do a
Dr. George Hudler, the head of the Plant Pathology Department at
Cornell University, Zingaro found what initial lab tests show to be
Phytophthora ramorum in trees in Pennsylvania and New Hampshire as
well as in the tree in New York.
have been submitted to the federal agriculture department's Animal
and Plant Health Inspection Service, but the results are not yet
that the nurseries are spreading this is false," said the outspoken
Zingaro, who has clashed with forestry officials in the past. "These
infections have nothing to do with California. As I and others have
been saying for over 10 years, the infection is opportunistic,
secondary and everywhere."
the New York find is strange in that there are no P. ramorum spores
on any of the understory host plants, which one would expect to
find. "If this is an infestation, it is doing something very
different than normal," she said.
the UC Davis plant pathologist who helped discover the pathogen,
said it's still possible that the area was contaminated, maybe even
by hikers who flew into nearby John F. Kennedy Airport from
California and then drove to the area.
"These days I
don't dismiss anything," Rizzo said. "It could be that it's native
there, but my guess is that if it was really there, somebody would
have picked it up before now."
Root of the
square off over causes and treatments of Sudden Oak Death
ecologist Lee Klinger, Ph.D., stands just beyond the grape arbor at
the Laguna de Santa Rosa watershed preserve in Sebastopol. It's
early October, and Klinger is about to lead a workshop. Participants
will whitewash an oak tree with a blend of mineralized rock salt,
hydrated lime, crushed oyster shells and water, spreading trace
minerals and oyster shells beneath the tree. This is the way Native
Americans and other indigenous peoples protected trees from pests
and diseases, and Klinger is trying to revive it. "We can't just
leave trees alone," he says. "They need to be tended, as the Indians
tended them. We've got a lot of work to do, just to catch up."
putting the group to work, Klinger announces that he is on a
mission. His goal, he says, is to alert as many people as possible
that Sudden Oak Death (SOD) is a sham, and that oaks and other trees
are in urgent need of care. "Most of the oaks and other trees that I
see are stressed, or extremely stressed," he says. "I see lots of
dead leaves and branches, and sparse growth." But Klinger's most
important point is to insist that "almost all the dying trees can be
saved. Most of them don't even show evidence of disease. For the
ones that do, the disease is secondary. They just need nutrition,"
he says, in the form of minerals that are rich in calcium. This is
holistic medicine for trees.
prevailing view of SOD, which reflects the thinking of the
pathologists that defined it, is that of conventional medicine:
identify a symptom and apply medicine to treat it. The cause, in
this case, is thought to be a fungus called Phytophthora ramorum,
and scientists are diligently searching for ways to control it. To
prevent the disease from spreading, infected branches and entire
trees are cut away. Nursery stock that is known to carry the fungus
is strictly quarantined, and forest officials urge hikers to wash
the soles of their shoes, bikers to wash their tires and dog owners
to wash their pets' paws when they leave an infected area.
different approaches are at hand in protecting California's trees,
one holistic, the other based on the disease model of conventional
medicine. Which approach is more likely to save our trees?
Californians would probably vote for the conventional approach,
which has the decided advantage of being the only one they have ever
heard of. It has the seal of approval of leading authorities,
including the University of California, the U.S. Department of
Forestry, the U.S. Department of Agriculture, the mainstream media
and such trusted elected officials as Congresswoman Lynne Woolsey,
Congressman Sam Farr and Senator Barbara Boxer. Since 1999,
according to Katie Palmieri, public information officer for the
California Oak Mortality Task Force--a coalition of public agencies,
nonprofit corporations and private interests--some $50 million has
been spent researching the P. ramorum fungus. Forest
pathologist Matteo Garbelotto, Ph.D., of UC Berkeley reports that
over the past four years he and UC Davis plant pathologist David
Rizzo, Ph.D., have each raised some $3 million alone for P.
authorities notwithstanding, Michael Prudhomme of San Anselmo, who
whitewashed his first tree at Klinger's Sebastopol workshop, prefers
the natural approach. "It makes total sense to me," he says. "I have
lots of healthy oak trees and a few that appear to be sick. I'm very
interested in learning ways to care for these trees."
gardener Scott Gough, the caretaker of trees on 1,000 acres in Lake
County, also believes that Klinger is on the right track. "What he
says makes much more sense to me than anything else I have heard,"
Gough says. "He has the comprehensive picture of the whole thing
that's going on with Sudden Oak Death. That's a big deal."
is a big deal. Klinger has led research projects in forest
ecology worldwide for 20 years, for the National Center for
Atmospheric Research, the University of Oxford, the Chinese Academy
of Sciences and other prestigious institutions. Explaining what
prompted him to settle in California in 2002, Klinger says, "A major
driving force was the fact that Sudden Oak Death was here, and I
knew I had a treatment and I knew it wasn't the fungus that was the
primary cause." Back then, he had high hopes of collaborating with
Rizzo and Garbelotto. These two respected scientists serve as
advisers to the California Oak Mortality Task Force. But Rizzo
turned Klinger down because his lab was concentrating on P.
single-minded focus of California scientists on a fungus is
difficult for Klinger to understand, particularly since he sees the
same fungus as an opportunistic species that takes advantage of
trees that are already dying of other causes. Explaining that P.
ramorum kills a tree by growing a canker around the trunk, and
that the canker "bleeds" black sap, Klinger says, "Most of the oaks
that are dying do not have bleeding cankers. Given this, P.
ramorum is not the best explanation for why the oaks are dying."
A better explanation for the cause of tree death, according to him,
is a bit more complex, involving mosses, soil acidification and tree
theory about tree death came together in 1985, when he was
researching a massive decline of old-growth trees on Kruzof Island
in southeastern Alaska. One day he noticed that wherever trees were
dying, thick growths of mosses covered the ground and the trunks. On
a hunch, he began digging and probing with his shovel, discovering
that there were no roots in the soil under the matted moss. His data
later confirmed that mosses are highly acidic and that runoff from
them causes soil acidification. Industrial pollution such as acid
rain, acid fog and other factors also contribute to soil acidity,
all of which harm tree roots. And that, according to Klinger, is
what's really killing most of the trees that are dying in California
and other parts of the world.
to causing tree roots to die, Klinger says that if "left unchecked,
mosses degrade bark and create spaces where fungi and beetles can
get in. The moss will very slowly bring a tree down. People must
tend trees and keep moss off them with whitewash. Bark is like skin,
and whitewash decreases acidity. But calcium is just a start. Trees
need trace minerals, too." Klinger's work on mosses has since been
confirmed, peer-reviewed and published in several scientific
papers--and so has his work on peatlands.
lots of ancient peat bogs on Kruzof Island, many older than 8,000
years," says Klinger. "I excavated the bogs. Buried beneath them, I
found large stumps and other remnants of the old-growth forest, a
younger stage in the development of the ecosystem." Intact stumps of
oak forests have also been found beneath peat bogs in the British
Isles. Klinger believes that in 1,000 to 2,000 years,
peatlands--bogs, fens and swamps--will replace many of the
old-growth forests of today. "They'll remain peatlands until they're
destroyed by fire, glaciers, floods or a rise in the sea level," he
findings baffle plant pathologist Ted Swiecki of Phytosphere
Research, a plant-science consulting and research firm based in
Vacaville. "Trees have had mosses growing on them for centuries," he
says. "Trees are capable of sustaining moss on their bark. Lichens
grow on trees, they're happy. It grows on healthy trees and diseased
trees, and has no effect. Anything that grows equally commonly on
trees has no effect."
consulting arborist Ralph Zingaro, who owns Bioscape Inc. in
Petaluma, agrees with Klinger. To make sure that California's
forests don't evolve into peatlands during his lifetime, he thinks
it's a good idea to take care of trees. But that depends on the
people of California. "Do they want a bunch of dead trees, or do
they want a bunch of live trees?" Zingaro asks. "The trees need a
good dose of calcium. Otherwise, we'll just let nature take its
course and we've got a bunch of dead trees. There's nothing wrong
with that. Let nature take its course. Some people will say, 'Great!
I need the firewood.'"
a forest ranger at Marin County's China Camp State Park, is a great
fan of the California Oak Mortality Task Force. "A completely
unknown disease was addressed so quickly and thoroughly by
scientists . . . ," he says. "This was like being able to watch the
black plague and identify the cause of it and prevent its spread."
He hastens to add, though, that the fight against SOD is not over by
a long stretch. "What we're looking at now is an unknown wave coming
at us," says Robards. "For example, some large, very beautiful huge
trees were still producing green leaves with P. ramorum all
over the trunk. They're dead now. In China Camp, if they were
anywhere near a targeted area, we felled the tree. Early last summer
we took about 170 trees out, and 99 percent were coast live oaks and
black oaks. The trees we didn't cut down are still falling."
soon be falling in Humboldt County, too, but for good reason, says
Rizzo. "We're not going to eliminate [SOD]. In Humboldt County,
where it's just getting started, we can target it and really slow
down the spread of it. We can manage it aggressively by removing
branches and some trees that are showing infection." Rizzo and
Garbelotto also recommend the one brand of phosphite (a chemical
compound) that the Department of Pesticide Regulation has approved
to protect oaks and tanoaks from P. ramorum. Arborists have
used potassium phosphite fertilizer for many years, and by 1999,
Zingaro had discovered its effectiveness with oaks that are showing
signs of stress.
after Zingaro persuaded him to conduct some experiments with
phosphite, Garbelotto was suitably impressed with the results. Last
year, he developed a new way to apply the approved brand. "The
reason trees are not treated in general is because though you may
have a product that works well, there is no way to make it go where
it's supposed to," he says. After considerable research, he found a
way to deliver phosphite directly to the P. ramorum fungus on
tree trunks and make it stick. "You just spray the compound on the
bark," he says. "Many scientists around the world are trying it and
having positive results."
impressive as the short-term results of phosphite may be, it
wouldn't be accurate to describe it as a magic bullet. Though the
brand approved for use against P. ramorum is classified as a
fungicide, it doesn't kill the fungus. "It doesn't directly affect
P. ramorum; it simply enhances the defense mechanism of the
plant," says Garbelotto. In addition, the manufacturer cautions that
its product may lose disease resistance with repeated use at high
As Rizzo and
Garbelotto continue to focus on P. ramorum, other researchers
are finding evidence that the true culprit may be the acidification
of California soils. Under a grant from the California Department of
Food and Agriculture, Robert O. Miller, an affiliate professor of
soils and crop sciences at Colorado State University, tested the
acidity of 50,000 samples of California soils, most from
agricultural land, some from forested areas.
we found that 22 percent of the soils were moderately or strongly
acidic and 4 percent were very strongly acidic," says Miller. "I'd
expect the agricultural market to be putting a lot of lime on their
soils." Over the past two years, Klinger and Zingaro have collected
130 soil samples from forested areas infected with P. ramorum.
After comparing Miller's data with the samples he and Zingaro have
collected, Klinger says "the Sudden Oak Death soils are much more
acidic than what Miller is finding."
Craig Peterson, who owns Arborworks in Marin County, is also testing
soils for acidity. "We've always been told that the coastal soils
here are rich in calcium and that they're always neutral or
alkaline," he says. "I have not gotten one alkaline reading. All the
trees are suffering from a lack of calcium."
strikes other researchers as "too acidic" is normal to Rizzo,
Swiecki and consulting urban forester Ray Moritz, who serves on the
Oak Mortality Task Force's executive committee. Moritz says that
during all 27 years that he has been testing Marin County soils,
they have always been slightly acidic. "The neutral or alkaline
soils are the exception, not the rule," he avers.
disputes claims that acid rain affects Marin County soils. "Sudden
Oak Death made its first recognized infestation in Marin County,
where 85 percent of the time the winds are out of the west-northwest
off the ocean. There is virtually no industry in Marin County, and
the first infestations and the first huge die offs of tan oak were
west of the freeway. Where would that acid rain come from?"
from the ocean?
off the California coast is not producing as much acidity as further
north," says Klinger. "But a significant amount is. The closer you
get to the coast, the more acidic is the rainfall and the more
acidic is the soil. The lower the calcium in the soil, the closer
you get to the coast."
And so it
goes. Just as Sudden Oak Death researchers see no evidence that soil
acidity and acid rain are harming California's oak trees, they also
see no evidence that calcium would help them. "I have yet to see any
sound data that any of our forest trees are calcium deficient," says
Ted Swiecki. "Calcium deficiency has various symptoms, and they
don't show up on our trees. If a tree is in a more stressful
situation or it's declining, it tends to be at much lower risk of
developing the disease. We don't know exactly what controls it, but
relatively vigorous trees are the ones that are [getting P.
reason enough to avoid calcium, says Garbelotto. "One of the main
concerns that I have regarding the use of calcium is that it appears
that plants that are very healthy become more susceptible to the
disease. P. ramorum likes plants that grow very well because
they produce a lot of sugar. To use anything that would potentially
improve the general health of the tree may not necessarily mean that
it's going to be protected from Sudden Oak Death."
University forest ecologist Tim Fahey, Ph.D., says, "It would be
highly unlikely that making trees more healthy would make them more
vulnerable to disease infections." Fahey recently witnessed a
striking regeneration of sugar maple seedlings after calcium was
applied to a forest damaged by acid rain.
is also getting encouraging results with calcium. Last spring, he
began treating the stressed trees under his care with whitewash,
crushed oyster shells and trace minerals. "I have been watching
these trees for five years," he says. "The ones we treated in the
spring showed signs within a month or two of clearly new, vigorous
growth patterns. It's obvious that they are getting better."
Klinger, the California Oak Mortality Task Force has accepted two of
his papers, one on acid rain and soil acidity, and the other on the
treatment that native peoples used to protect the trees they relied
on for food, shelter and fuel. In January, Klinger will make formal
presentations on both papers at the Sudden Oak Death Science
Symposium in Monterey. He only wishes that he could reach more
could just know that there's a simple, nontoxic treatment that has
been used for thousands of years and that all this talk about the
fungus killing the trees is driven by the disease model, and the
disease model isn't working in human health and it doesn't work in
tree health either," he sighs.
could just know that the ways that indigenous peoples cared for
trees is tree care at its finest."