California remains on alert for the greatest threat ever to its wine industry. But finding a solution to save its grapes from Pierce's disease and the glassy-winged sharpshooter remains elusive.

Growers on California's North Coast are keeping a sharp eye out for the tiny insect called the glassy-winged sharpshooter, which is threatening the state's wine industry.

The sharpshooter doesn't do much damage on its own, but it spreads a bacterium that causes Pierce's disease, a fatal and incurable disease that kills vines within two to three years. It already has devastated vineyards in southern California and spread as far north as Sacramento in the northern part of California's Central Valley. There are fears that the sharpshooter will make its way to the coast in sufficient numbers to cause havoc in Napa and Sonoma, the heart of the state's premium wine industry.

A solitary sharpshooter and two masses of sharpshooter eggs were found in mid-September in Sonoma, but none have turned up since. Nevertheless, plans are being laid for ground spraying and tight restrictions have been imposed on shipment of nursery stock into the north coastal area.

Andy Beckstoffer, who farms more than 1,000 acres of vines in Napa and Mendocino counties, believes that there is a "better than even chance" that with proper diligence and locally applied spraying, the North Coast can escape the severe damage suffered in southern and central California.

"We have to be vigilant and step in with a spraying programme at the first sign of the sharpshooter," Beckstoffer said. "If we do that and don't go to sleep on it, we should be all right." Napa is particularly at risk, he added, because the bacterium that causes Pierce's disease is present, but it lacks an efficient host.

Meanwhile, stiff opposition to any spraying plans have surfaced among environmental groups, who fear that sprays will drift into private property and also hurt organic farmers who supply fresh produce for San Francisco's booming restaurant business.

Nick Frey, with the Sonoma County Grapegrowers Association, said opposition to spraying is a potential problem. "We would seem to be headed for a confrontation should the need to spray arise," he said.

The concerns over the glassy- winged sharpshooter and pesticides are heightened by a growing concern on the North Coast over the rapid expansion of vineyards. In 1999, for example, 9,000 acres of grapes were planted in Sonoma County, bringing the total to 52,000 acres. Sonoma County Agricultural Commissioner John Westoby said that county residents were demanding more input on whether to spray or not to spray.

Green - Areas at Risk
Red - Infested Areas
California Department of Food and Agriculture 4/8/2000

Opponents of spraying are calling for greater reliance on biological controls, such as the Mexican parasitic wasp that has been introduced into a test vineyard in southern California. Early results show the wasp may be effective as much as 80% of the time. "Like all biological controls, the wasp solution is not perfect, but it would be a big help in reducing risk of the sharpshooter spread," Frey said.

Greg Nelson, director of the North Coast Grape Grower Association, said: "We don't have any experience with this creature, and the reports are startling on how prolific and what a tough bug it is,'' said Greg Nelson, a Mendocino County grower. ``We know how many the officials have found, but what they don't know is how many got away.''

Last year, direct and indirect losses from Pierce's disease totaled about $46m, according to Martin Mochizuki of the North Coast Pierce's Disease Task Force.

Pierce's Disease has been endemic in California vineyards since the 19th century. In the past, it has been spread by the blue-green sharpshooter, a smaller and far less mobile insect than its larger cousin, which mean the outbreaks were smaller and easier to control.

"There will be some tough decisions made if we're going to protect this industry and prevent this pest from getting a foothold here," Napa County Agricultural Commissioner Dave Whitmer, told the San Francisco Chronicle.

"If we get into a situation where we can't grow wine grapes here, the economy is severely affected,'' Whitmer said. ''People come here for the wineries and stay at country inns. None of that would happen if we grew rutabaga.''