'SUDDEN OAK DEATH' PLAUGES MARIN
By Richard Halstead
Excerpt from The Marin Independent Journal


Look closely at Marin's hillsides, and you'll see the telltale blemishes of the scourge - the wilted, brown canopies of dying coast live oaks that wreath the landscape. "Just driving down the freeway you can spot the dead oaks quite easily now," said Mike Greene, an arborist with Bartlett Tree Experts in San Rafael. Once the eye is educated, the lifeless skeletons seem to multiply - one here, another there, an entire stand of dying trees close by. The full extent of the problem, however, remains masked. "There are trees under attack right now that are still green. People will see them turning brown over the next few weeks. So this problem is getting worse even though people may not see it right now," Greene said. Something is killing the live oaks and their cousins, the tanoak, by the tens of thousands. From Mendocino County to the north and Big Sur to the south, the epidemic, first spotted in 1995 in Mill Valley, is spreading. "I've never seen this widespread a mortality in any of the oak woodlands in the state," said Rick Standiford, associate dean of forestry at the University of California at Berkeley. But the cause of what is being called "sudden oak death" remains a mystery. "We're still dealing with an unknown causal agent," said Marin County Agricultural Commissioner Stacy Carlsen.

Basing their research in Marin, a team of University of California plant pathologists, entomologists and oak ecologists are trying to isolate the variables and piece together the puzzle. Meanwhile, a consortium of Marin arborists, horticulturists, and public officials has formed to advise an increasingly concerned populace. The stakes are huge. The oaks are a key part of the forest ecosystem. The loss of decorative live oaks will be a major blow to property values. And the death of large numbers of the trees will leave Marin more susceptible to a major wildfire. "It's much worse than people have any idea," Greene said. Scope of the problem. Although the disease was spotted at least five years ago, questions connected with the phenomenon far outnumber answers. Researchers lack even a good estimate of the number of trees dead or infected. That should change soon.

Researchers have established 20 half-acre plots - in China Camp State Park and the Marin Municipal Water District watershed around Mount Tamalpais - that they're analyzing. The condition and location of each oak on these plots was first charted using Global Positioning Satellite technology. At the end of March, aerial photographs were taken of the plots. The infrared photographs will allow researchers to identify trees that appear healthy to the human eye, but whose leaves already are displaying the reduced moisture flow associated with the disease. In the study areas, 20 percent of the oaks are standing dead, and another 40 percent are already sick, said associate dean Standiford, who is overseeing the research team. The U.S. Forest Service is contemplating aerial photography over a much wider area later this year.

Emergence in Mill Valley
The disease was first officially identified among tanoaks in Mill Valley's Blithedale Canyon by Pavel Svihra, a horticulturist with the California Cooperative Extension Service. Initially, Svihra mistook it for a common oak root fungus. But the rate at which the trees wilted and died, a matter of weeks, quickly indicated otherwise. Soon more oaks started displaying the same symptoms: beginning with the oozing of a burgundy-red sap from their trunks that resembles blood. Svihra sounded the alarm but many foresters at the time weren't listening. "It's a minor peak in a natural cycle," Bruce Hagen, an urban forester with the California Department of Forestry, was quoted as saying in 1998. "I could not get people to understand the magnitude of this," Svihra said. That has all changed. Offensive mounted. Early this year, Supervisor Cynthia Murray led the effort to create a local task force to address the growing crisis. Murray convinced the county to chip in $5,000 and helped secure a $20,000 grant from the Marin Community Foundation to help pay for a task force coordinator. "The way this disease has moved from tanoaks to live oaks and now to black oaks is very frightening," Murray said. When Murray stepped in, Svihra was struggling to get the money to print informational brochures to distribute to homeowners. "It was overwhelming us," said Ellie Rilla, director of the university's extension program in Marin. The Marin Community Foundation will "certainly" consider additional funding if requests are made, said foundation chief executive Thomas Peters. "We haven't been approached yet," Peters said. The University of California has allocated about $50,000 to accelerate research into the cause of the oak deaths. Standiford also hopes to secure a $70,000 grant from the U.S. Forest Service.

Answer to the riddle
The culprit could be a fungus, bacterium or virus. Slices of diseased trees have been sent to several labs for testing. So far, no pathogen has been identified. New DNA analysis techniques will be tried next, said Brice McPherson, a University of California entomologist who began researching sudden oak death full time this year. "If we had more money, we could do a better job," Standiford said. Unlike agricultural products like wine grapes or tomatoes, there is no association to finance research of oak diseases, said arborist Greene. And it's uncertain whether finding the cause will solve the problem. "Whether what we find leads to a cure is completely up in the air," McPherson said.

Death takes wing
One thing is undeniable: the plague is a banquet for bugs. From inside trees that are dead or dying, tiny black beetles, about the size of a grain of rice, are now emerging and taking wing by the millions. The beetles can smell the sickness in the air. A pungent alcoholic odor emitted by distressed trees allows beetles to hone in on their targets. When a beetle finds a new victim, it uses the chemical language of insects - secreted pheromones - to broadcast the news to others. They descend on the hapless tree in hordes and bore into it: tiny mounds of sawdust, caused by the boring, spot infested trees. The beetles lay new eggs and introduce a fungus to feed the larvae. The construction of the egg galleries girdles and plugs the vessels in the outer sapwood that transport water and nutrients to the tree crown. The tree literally strangles to death. New broods of beetles emerge from the trees about twice a year - in spring and early fall. The role beetles play in killing the trees is still being debated. It is possible that the beetles carry and spread the disease. Typically, beetles kill only weakened trees. Some trees in which the flow of nutrients were blocked were dying before any beetle arrived, Standiford said. A dark, green fungus, hypoxylon, usually appears on the outer bark of dying trees. But researchers also question whether it is the ultimate cause of the trees' demise.

Global economy's price?
One possibility is that sudden oak death is caused by an exotic fungus. Similar oak die-offs have occurred recently in Mexico and Japan. "In my mind, it could easily be something exotic," Standiford said. Exotic fungi wiped out nearly all of the nation's chestnut trees at the end of the 19th century and, more recently, a majority of the country's elm trees. It is believed that a beetle carrying the Dutch elm fungus was transported to the U.S. on a log from Europe, Standiford said. As with human ailments, growing international mobility has greatly increased the spread of exotic plant diseases, Standiford said. In addition to imported logs, disease-carrying insects can hop a ride in the lumber used in marine freight containers, he said. "Our global economy has given us the chance to bring in global diseases from all over the world and it creates some real pressures on our native ecosystems," Standiford said. For example, the Northern California wine industry is trying to control the spread of an insect that carries Pierce's disease, a vine-crippling bacterium. It is believed that the bug was introduced to the state via ornamental plants from the southeastern United States. Do oaks face the same devastation as the chestnuts and the elms? "There is a chance - how high a risk, we don't know," Standiford said.

Along the barricades.
The lack of knowledge about what is causing the epidemic has triggered frustration among homeowners who are desperate to protect their treasured trees, Svihra said. "People are looking for a magic pill," Svihra said. None exists. Right now, the best advice he can give people is to spray healthy trees with Astro to protect them from beetle invasion. The spray - a relatively environmentally friendly pesticide - seems to help even trees that are already infested, as long as the bugs haven't reached critical mass, Svihra said. Some panicked homeowners want to spray every tree in sight, Svihra said. But he and agricultural commissioner Carlsen advocate a measured approach. It does no good to spray trees that are completely overwhelmed by beetles, and it is not prudent to spray oak trees lacking evidence that beetles are in the vicinity, Carlsen said. Ralph Zingaro, owner of Bioscape, makes no apologies for his no-holds-barred approach to responding to sudden oak death. "We're aggressive; we don't mess around. We're in the business of saving trees," said Zingaro, whose techniques include injections and topical applications of fungicides. Zingaro was hired by Nicasio resident John Wick to help save oak trees on his 439-acre ranch in Nicasio. In March, Wick paid to have 105 beetle-infested live oaks cut down, and removed from a steep section of his property by helicopter. The alternative - covering all the trees in plastic to trap and kill the beetles inside - would have created an eyesore on the property, Wick said. Thousands more oaks remain on the property. "I love the oaks. It is just heartbreaking to cut them down," Wick said. "The spectacular oaks along the ridgelines are part of the reason we bought the place," he said. Wick is sparing no expense to protect the remaining trees. On Zingaro's recommendation, he has hired workers to expose the root crowns of 4,000 oak trees so that a fungicide can be injected into them. He has also paid for soil tests. "We've taken hundreds of soil samples, thanks to the Wicks," Zingaro said. He says the soil's acidity is elevated. "There is something going on environmentally," Zingaro said. Horticultural adviser Svihra said oaks may have been weakened by recent droughts and increased development in the county. Standiford, however, doubts that environmental factors are responsible for the spread of the disease. Zingaro wouldn't say how much the Wicks have paid for his work. "But what they're paying us is a fraction of what these trees are worth. They're worth millions," Zingaro said. Kenneth Bovero, owner of Marin County Arborists in San Rafael, has also assisted with Wick's oaks. Bovero said he experimented with fungicides three or four years ago but has given up on them. "I didn't have a lot of success," Bovero said.

The disease showed up at George Lucas' 6,000-acre Skywalker Ranch in Lucas Valley about two years ago, said spokesperson Jeanne Cole. "It's affected hundreds of trees. It's very, very sad," Cole said. Lucas is spraying trees on the valley floor adjacent to his buildings, she said.

The money pit
Tree owners are upset for a very good reason, said Ray Moritz, an arboricultural consultant based in Mill Valley. A U.S. Forest Service survey in 1971 found that trees contributed as much as 27 percent to appraised land value, Moritz said. "With the loss of these trees, people are going to lose a tremendous amount of property value," said Moritz, who has appraised single live oaks in Marin at more than $30,000. Sudden oak death "is a sudden hit to your checking account, too," said Rick Fraites, a Novato resident who recently lost his fourth live oak. Fraites started spraying his oaks after he discovered three dead trees at the end of last summer. He had the first three chopped down and disposed of by a tree service to minimize the risk of contagion. "This one must have been infested before we got to her," Fraites said. "I love the trees and the wildlife they bring. I hope we can get this under control, and it doesn't get catastrophic," he said.

Fuel to the fire
A catastrophe is just what could result if a fire were to break out now in the county's forested open space, firefighters say. The dying oaks are adding to the county's already heavy fuel load. The trees are particularly dangerous while the dead leaves remain on their branches, said Mike Swezy, a resource specialist with the Marin Municipal Water District. A fire now would "fly through the crowns" of the trees, Swezy said. Initially, the disease killed tanoaks, located in the cooler, more moist areas of the water district's 20,000 acres of open space, Swezy said. More recently, it has showed up in large numbers of coast live oaks and has been seen in some black oaks. Oaks are one of the most common types of trees on water district lands. There are probably 10,000 tanoaks alone, Swezy estimates. Some tanoak groves have been decimated. "There are places that look like somebody dropped a defoliant," Swezy said. "They create a suppression nightmare," said Tim Walsh, a fire captain specialist with the Marin County Fire Department. The loss of the trees will also open up the forest canopy and pave the way for highly flammable grasses and weeds, such as Scotch broom, Walsh said.

Ecological reverberations
The impact on the overall ecosystem of the forest is unpredictable, said Dennis Odion, a vegetation ecologist with the water district. The acorns, which the tanoaks supply in plentiful numbers, will be sorely missed by numerous animals including quail, squirrels, deer and wood rats, Odion said. Conservationists estimate more than 300 species of animals, more than 5,000 types of insects, and 130 rare, threatened or endangered plant species rely on oak habitat. "The oak tree is the centerpiece of the ecology here in Marin," said Mill Valley resident Phyllis Faber, a member of the California Native Plant Society. "The loss is potentially horrendous. It could change the nature of the state." The loss of the oaks could also diminish the watershed's ability to collect water, and could even affect the weather, Faber said. Said David Chipping, the Plant Society's vice president of conservation: "If the oaks went, the whole coastal ecology would collapse."

Contact Richard Halstead via e-mail: rhalstead@marinij.com
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