State OKs Pesticide That May Help Fight Sudden Oak Death

The state has approved the use of a pesticide that could help protect oaks from a wide-ranging forest disease that has killed tens of thousands of trees along the Northern and Central California coasts.

But the treatment will have limited use and researchers stressed that it is not a cure-all for sudden oak death, a fungus-like disease found in 12 California counties.

“The likely areas where the treatment would be used include mostly private-owned land, but trees around high-use facilities in public parks may also be potential candidates,” said UC Berkeley researcher Matteo Garbelotto, whose experiments have found the compound effective in preventing or slowing infection. “It’s really meant for individual oaks or tanoaks that are at high risk for infection.”

First observed in 1994 in Marin County, the disease has infected more than two dozen tree and shrub species, including several types of oak, coast redwood and Douglas fir. Hardest hit have been oaks and tanoaks, in which it has proved more likely to be lethal than in some other plant types.

The treatment, a phosphorous compound sold under the brand name Agri-Fos, is a fungicide that has been used for a number of years to fight other plant infections.

Garbelotto’s experiments found that the compound, which can either be injected into the tree or sprayed, stopped growth of the pathogen if used in the early stages of infection in oaks and tanoaks. Its effectiveness has not been tested in other plant types, and it is not anticipated that it would be used in large wild-land tracts.

“As far as widespread spraying in national forests ... that’s not what they recommend at all,” said Sarah Yang, a UC Berkeley public information representative. “They haven’t proven that would be helpful. It didn’t kill the pathogen. It just stopped it.”

The treatment, approved Wednesday by the state Department of Pesticide Regulation for use by licensed pesticide applicators, is so far the only one registered with the state to combat sudden oak death.