"It's an important symbolic victory for biotech's skeptics," Conko said. "It certainly is something that should make supporters of biotechnology, including myself, a little bit nervous."

Activists gathered 9,000 signatures -- more than needed to qualify the measure -- which county supervisors now may enact or put to voters in a special election as soon as May or June. If the measure is approved, Sonoma would become the fourth California county to ban raising genetically engineered foods.

Genetically modified wine grapes are not grown in Sonoma County but farmers are interested in using genetic engineering to develop products to replace pesticides, said Ben Drake, chairman of the California Association of Winegrape Growers.

Without biotechology, Sonoma County's world famous wine industry could be disadvantaged, said Henry Miller, a Hoover Institution fellow and past director of the US Food and Drug Administration's office of biotechnology.

"A ban could remove important technological tools for combating significant economic problems such as Pierce's disease," said Miller, author of the "The Frankenfood Myth: How Protest and Politics Threaten the Biotech Revolution."

The vine-killing disease is spread by the glassy-winged sharpshooter insect. Several colonies of the pest were discovered last spring in northern California.

Activists claim the value of biotech crops is outweighed by unknown health and environmental effects, a message they expect will resonate in Sonoma County as in neighboring counties.

"We talk about healthy farms and healthy organic foods for our counties, that's our trademark," said Frank Egger, a northern California environmental activist. "Stopping genetically engineered crops is an enhancement and a protection for today's farmers."

Voters in neighboring Marin County, an affluent area north of San Francisco, approved a ban in November. Last March voters in Mendocino County north of Sonoma County passed the nation's first county-level ban on genetically engineered crops.