Forest officials in Humboldt County have launched a counterattack against an oak-killing disease that has been marching north in recent years.
Beginning last week, crews began to hack down and burn tan oak and California bay trees infected with the pathogen that causes sudden oak death, killing oak stands in more than a dozen coastal counties. The 50-acre stand being treated is in Humboldt Redwoods State Park between Miranda and Myers Flat along the Avenue of the Giants.
"We think this is a very strategic place to make a stand at," said Yana Valachovic, forest adviser for the University of California Cooperative Extension.
The disease, caused by the fungus-like pathogen Phytopthora ramorum, is more widespread in Humboldt County than it was only a few years ago. Surveying has found the disease to have spread from the Redway area where it was first detected in the county.
Scientists believe there are two forms of the disease, Valachovic said, one that kills oaks and one that just causes die-back on leaves and twigs. The idea of the experiment is to find out if removing the most productive hosts of the disease -- in this area bay and tan oak trees -- and reducing the abundance of spores can check its expansion to the north.
California Department of Forestry crews will pile branches and leaves and burn them, leaving logs on the ground, Valachovic said. She also hopes to burn the forest floor in some areas to compare that method with piling and burning.
There is reason to believe that it can make a difference. In 2004, the cooperative extension and the Humboldt County Department of Agriculture cut
an infected stand of bay trees in Redway, which appears to have kept sudden oak death from spreading in that area.
Aerial surveys by the U.S. Forest Service's Sudden Oak Death Monitoring Program continue to spot dying oaks, including in Northern Humboldt and in Del Norte counties, said Jeff Mai, a biologist with the program. Tests at the ground level show many of those trees are dying from other, native diseases, he said.
It's possible that the moisture-loving sudden oak death pathogen got a push from the warm, wet spring of 2005, and Mai expects that where it finds a suitable climate, it will thrive.
He said the Humboldt County effort is a huge undertaking, but not a fruitless one. Still, working on public property may be much easier than tackling the disease on various and vast private lands in the area, where participation in any such effort is voluntary, Mai said.
Mai also said that similar efforts in Curry County, Ore., appear to have had some success.
"Time will tell," Mai said.
Valachovic said there are no other ways to defoliate the trees on a broad scale other than using chain saws and fire. But the area that has to be contained has gotten bigger than Valachovic would like, and that will be a test for those methods.
"Is it too late? I don't know," she said. "We're trying."The Times Standard
