SAN FRANCISCO -- California's drought appears to be reducing the spread of a disease that threatens to wipe out huge swaths of oak trees in the state, a newspaper reported.
Preliminary results of surveys taken between April and June show between 2 and 10 percent of California bay laurel trees in 17 western counties tested positive for sudden oak death. Bay trees are major hosts for the pathogen and spread it to oak trees.
The infection rate for bay laurels is between 20 and 80 percent when rainfall is plentiful, the San Francisco Chronicle reported on Sunday (http://bit.ly/V5IVXM ).
Sudden oak death has killed hundreds of thousands of oak trees in California. Scientists say the drop in the infection rate gives them a chance to go on the offensive and target the host bay trees.
Seven trees were taken down recently in one area.
"The approach is to basically inflict a strike on the pathogen so that it will exist in fewer places and, as a result, its outbreaks will be smaller," said Matteo Garbelotto, who heads the Forest Pathology and Mycology Laboratory at UC Berkeley. "When we take down these trees, we are taking away the place where the disease finds shelter during these harsh times. We can't get rid of the pathogen, but maybe we can go from having 70 percent of the oaks being killed to maybe less than 5 percent of the oaks being killed. That's really, really significant."
The surveys were conducted in counties between Fort Bragg and San Luis Obispo by volunteers. Researchers at Garbelotto's lab analyze the results.
Information from: San Francisco Chronicle, http://www.sfgate.com