Oak disease attacks redwoods, Douglas fir
Discoveries in Sonoma, Santa Cruz counties confirm scientists' fears, will trigger new restrictions on logging

By MICHAEL COIT/THE PRESS DEMOCRAT/September 5, 2002

The disease killing California's oaks also threatens the state's majestic redwood groves, scientists said Wednesday, citing findings from Sonoma and Santa Cruz counties.

Researchers said the disease also was found on Douglas fir.
UC scientists aren't yet certain if the disease will prove fatal to either tree, but they said the findings confirm their worst fears about the disease, which has killed tens of thousands of oaks trees.

"This is kind of a worst case scenario," UC Berkeley scientist Matteo Garbelotto said. "Those two hosts are not only ecologically important but also economically important."

Garbelotto and UC Davis scientist Dave Rizzo discovered the microbe that causes sudden oak death and have led the effort to find a cure. They said redwoods and Douglas firs are essential to the health of coastal forests.

Gov. Gray Davis said Wednesday's announcement "significantly raises the stakes." He called on President Bush to provide $10 million to bolster $2 million in new state funding to fight the disease.

The spread into redwoods and Douglas fir means logging companies will face new restrictions under state and federal quarantines aimed at preventing the disease from spreading beyond 12 coastal counties where it has been found.

Scientists were surprised that the disease moved into the two trees because they are conifers and far different from oaks and the other host plants.

Sudden oak death appears to spread more easily than most plant diseases.

The two types of conifers bring the number of affected plant families to 10 with a total of 17 specific hosts.

"Not all diseases kill everything. But now that we have these two hosts, almost every woody plant species in all these forests in the coastal areas can be infected," Rizzo said.

"Now, each one of those hosts is going to be impacted in a different way. But the cumulative affect may change a lot of ecosystems. It's just going to look different," he said.

The disease might wipe out some host plants and shrubs and reduce forest diversity. In other instances, tree stands could be diminished.

Above Glen Ellen in Jack London State Park, where some of the infected redwoods were found, the disease already has wiped out many tanoak stands and killed some coast live oaks.

"If redwoods are affected, that would certainly be alarming. You're covering most of the trees that occur in the plant communities of the parks," said Greg Hayes, a supervising ranger for the state park's Silverado District, which covers areas of Sonoma, Napa and Lake counties.

At Jack London Park, he said, "the groves that we have are significant because they're often along creek areas and trails that pass through mixed vegetation. They provide the shade in the park that make it possible for people to hike through on hot summer days."

The infected Douglas fir trees were found in Fairfield Osborn Preserve, the research site Sonoma State University operates east of Rohnert Park on the other side of Sonoma Mountain from Jack London. The disease has killed a black oak and some coast live oaks there.

"We're losing individual trees on a case-by-case basis over time," said Julia Clothier, preserve manager.

While Clothier said there's plenty of fear about how the disease might progress, she also said findings made at the preserve and other sites have helped scientists learn more about how the disease spreads and harms plants and trees.

"It's nice to be at the center and to have those discoveries being made here," she said. "We're just learning about this. Something's going on and it's interesting."

On both redwoods and Douglas fir, needles and very small branches turned brown, with the fir branches wilting or dying.

Only saplings appeared infected and the disease was not observed on trunks. But scientists cautioned that not enough is known to assess whether trees might die or other potential ecological impacts.

The other known hosts are: Coast live oak, black oak, tanoak and Shreve oak, rhododendron, manzanita, California huckleberry, madrone, California bay laurel, California buckeye, big leaf maple, California coffeeberry, Toyon and California honeysuckle, as well as arrowwood in Europe.

Sudden oak death has been found in 12 counties, including Sonoma, Napa and Mendocino.

State and federal quarantines aimed at keeping the disease in check regulate the movement of host trees, plants and materials out of those areas and California.

Redwoods and Douglas fir are two of the state's most heavily logged trees.

While timber companies remove branches before hauling logs out of forests, a quarantine requirement to also remove bark could hamper operations and limit the use and sale of some products.

"We need to make sure it doesn't become a huge bottleneck," said David Bischel, president of the California Forestry Association.

Timber companies operating in the four logging counties covered by the quarantine -- Humboldt and Mendocino, and to a lesser degree Sonoma and Santa Cruz -- now haul some of their trees to mills outside those counties. Bark is removed at the mills for a variety of uses.

Bischel said the restrictions don't seem reasonable given that their foresters have not found sudden oak death on lands where trees are cut. "We've been managing those forests and we don't find it in those forests," he said.

Scientists noted the quarantine is needed given the range of the two trees.

Redwoods are found in coniferous forests and range along the coast from the Oregon border to Monterey.

Douglas fir are found in hardwood and coniferous forests and range from British Columbia to Santa Barbara County and east into the Rocky Mountains.

Coastal woods also are a major draw for hikers, campers and other visitors to state and national parks. Signs have been posted in some parks urging users to wash boots and bike tires before leaving and not to collect wood or plants.

Sudden oak death was first observed in Marin County in 1995. Five years later, Garbelotto and Rizzo identified the cause: a fungus-like microbe called Phytophthora ramorum, which is related to the fungus thought to have caused the Irish potato famine and the death of Port Orford cedar trees in the Pacific Northwest.

Experiments have revealed that the microbe survives in rainwater, soil and leaf litter.

Scientists suspect it spreads through the air and infects host plants other than oaks and then is spread to oaks in rain splash. The microbe apparently builds up in bay foliage and then spreads to oaks.

You can reach Staff Writer Michael Coit at 521-5470 or mcoit@pressdemocrat.com.

Return to previous page