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Disease Adds Redwoods to Its Victims

Flora: Sudden oak death is found in coastal varieties and in Douglas firs. The contagion has attacked 16 species of trees and shrubs.

September 05, 2002|BETTINA BOXALL | TIMES STAFF WRITER

Researchers have confirmed that one of California's most treasured trees, the coast redwood, has been infected with a highly contagious disease that has killed tens of thousands of oaks in the last several years.

Testing by University of California scientists shows that the Douglas fir also is susceptible, bringing to 16 the number of species of trees and shrubs that have been attacked by the disease--sudden oak death--in California.

Redwoods and Douglas firs are by far the most commercially valuable of the infected species, although the fungus-like disease, for which there is no cure, has so far been detected only in saplings and sprouts of the two species.

"What we think it means for commercial timberlands is nothing at this point," said Donn Zea, president of the California Forest Products Commission. "We haven't found anything."

The two tree types will immediately be subject to state and federal quarantine rules governing the movement of plants and tree products affected by sudden oak death. But it does not appear that the regulations will interfere with commercial lumber production to any significant degree.

Scientists said it was too soon to predict the disease's long-term impact on redwoods, which grow to towering heights and can live for two millenniums.

"By looking around, we have no indication this is really killing mature trees," said Matteo Garbelotto, a UC Berkeley adjunct assistant professor and a leading researcher on sudden oak death.

Testing by Garbelotto and UC Davis plant pathologist David Rizzo found infected redwood saplings at Jack London State Park in Sonoma County and Henry Cowell State Park in Santa Cruz County. The infected Douglas fir saplings were found on state research station land in Sonoma County. Researchers also have found DNA evidence of the disease on redwood sprouts in Marin, Alameda and Monterey counties, suggesting that it is in a number of locations.

"We think on redwood it's quite widespread," Garbelotto said.

Since it was discovered in Marin County tanoaks in 1995, sudden oak death has been found in a variety of trees and shrubs growing in the coastal forests of Central and Northern California.

"We have rarely seen a pathogen affecting so many different host species in the ecosystem and so many different parts. So what is the cumulative effect in time?" Garbelotto wondered. "Is it going to affect the overall productivity of the forest?"

The infected species have exhibited varying degrees of resistance to the disease, with tanoaks appearing to be the most susceptible. The infection could greatly reduce the tanoak population, which, though not commercially valuable, is important to wildlife.

Sudden oak death has been found in 12 counties, extending south from Humboldt to Monterey. The farthest inland it has been detected is Solano County.

Among other species affected are coast live oak, Shreve oak, big leaf maple, manzanita, madrone and California bay laurel.

Bay, madrone and tanoaks seem to play the greatest roles in spreading the disease, which is carried by spores that can travel through the air or in moist soil.

Regulators for months have been trying to iron out differences between federal and state quarantine rules on sudden oak death. So far neither set has had a major commercial impact.

"We think this is a very workable situation, and we want to do everything to make sure the disease is not spread into our commercial timberlands," said Zea of the Forest Products Commission.

Federal rules require logs to be debarked and certified free of the disease before they can be shipped out of state. Zea said inspections for the disease are already a standard part of timber harvest plans. And mills, where logs are usually debarked, are typically in the same county as logging sites. Some companies, such as Pacific Lumber, one of the state's leading producers of redwood, burn the bark to produce electricity, something they would still be allowed to do.

Selling bark for use as commercial garden cover may be another matter, but regulators could not say Wednesday exactly how that market might be affected.

In the wake of Wednesday's infection news, Gov. Gray Davis said he was asking President Bush for $10 million in federal funds to fight the disease.

"Today's announcement about sudden oak death in Douglas fir and coast redwoods significantly raises the stakes," said Davis, adding that the state is allocating $2 million this year to supplement $3.6 million approved last year.

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