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Oak-killing disease found on a tree in New York state
Case on East Coast raises new questions

Peter Fimrite, Chronicle Staff Writer

The discovery 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.

The infected 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.

Forestry 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 southern Oregon.

"Nobody knows 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."

An intensive 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."

Sudden oak 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.

A nationwide 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 restrictions.

"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."

The Nassau 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 survey.

Working under 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.

Those results have been submitted to the federal agriculture department's Animal and Plant Health Inspection Service, but the results are not yet complete.

"The notion 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."

Britton said 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.

David Rizzo, 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."

E-mail Peter Fimrite at

Root of the Problem

Scientists square off over causes and treatments of Sudden Oak Death

By Tara Treasurefield

Forest 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."

Before 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.

The 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.

But two 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?

Nature vs. Nurture

Most 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. ramorum research.

Leading 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."

Landscape 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."

Root Causes

It really 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. ramorum.

The 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 roots.

Klinger's 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.

In addition 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.

"There are 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 says.

Klinger's 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."

But 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.'"

Magic Bullet?

Pat Robards, 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."

Trees will 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.

In 2002, 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."

But 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 rates.

Building Stronger Trees

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.

"Statewide, 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."

Arborist 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."

But what 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.

Moritz also 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?"

How about from the ocean?

"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. ramorum]."

That's 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."

But Cornell 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.

Scott Gough 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."

As for 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 Californians.

"If they 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.

"If they could just know that the ways that indigenous peoples cared for trees is tree care at its finest."










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