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— Does the blue-green sharpshooter spell doom for San Diego's nascent wine industry? The question is serious for the county's largest winery, Escondido's Orfila Vineyards. This year, with a combination of a warm, wet winter and lush growth by the San Dieguito River, conditions are ideal for a population explosion of vine-sucking sharpshooters. After eating out the riverbank growth, the half-inch locust lookalikes will likely spread to munch through the 32 acres of spring leaves on Orfila's vines.

Sucking vines is one thing. Trouble is, the sharpshooters bring with them, hiding in their mouths, a bacterium that transfers into the vines, multiplies, and strangles the plants, slowly. The condition, known as Pierce's Disease, is the "single most formidable obstacle to the growing of European-type grapes" in California, according to Alexander Purcell, a professor of entomology at U.C. Berkeley.

This year, Leon Santoro, Orfila's manager and winemaker, is bracing for a major attack. He already has vines dying right outside the grape arbors where guests picnic and taste his wines.

"Look," says Santoro, 47, standing among his Chardonnay vines. He puts his hand on a bare plant. "This vine is probably a goodbye. A no-no. Pierce's Disease. Overall in the vineyard, I'm trying to limit the number of plants I have to dig up to about 5 percent. I'm an optimist. I hope I'm not fooling myself when I say 5 percent. Yet even that means losing over a thousand vines per year."

Here in the field of Chardonnay vines, the percentage is higher than 5 percent. "This plant will probably die before September. We just keep putting in more vines behind it. How many young vines do you see, and how many old vines? I'd say it's more like 10 to 15 percent of the Chardonnay vines [that have been struck by the disease]. Five years from now, there'll probably be no Chardonnay here. This is our last attempt at planting Chardonnay."

"Some growers are going to be wiped out by this," says county agriculture farm advisor Vince Lazaneo. "It won't happen overnight. It'll take several years. But certainly some growers are going to be wiped out."

It wouldn't be the first time. Back in 1882, also a period of warm, wet years, the sharpshooter, which is closely related to the cicada, discovered how delicious the imported grape vines were -- and devastated the Southern California wine industry. The disease completely eliminated viticulture from coastal L.A., the Santa Ana River basin, and most of San Diego's then 7000 acres of vines.

Now, a century later, the county has only 94 acres of vines. Seventy-seven of these produce for Orfila. Despite the small beginning, San Diego is starting to be taken seriously as wine-producing region again. "We made 20,000 cases of wine last year," says Santoro.

But the dreaded Pierce's Disease is back, encouraged by El Niño, spreading up from the San Dieguito River to nearby Escondido vineyards. San Diego County's vineyards were among the first to be threatened in the state, because of their location in the warm and unusually wet south.

Leon Santoro walks down his gentle hillside overlooking the San Dieguito River valley. To his right, the velvet green of a golf course, and beyond, million-dollar homes overlooking it. Here, the fields are strung with wires holding up rows of trained vines just coming into their green mantle. The branches of most have been trained into chest-high horizontal "H" shapes, for maximum exposure to sun and easy picking.

It takes a moment to realize the greening is uneven. Santoro points out plants with bare branches. Others with smaller leaves. "We've been fighting this since '94, when I became aware of it," he says. "The sharpshooter comes into the vineyard and feeds on the leaves. Not biting like a locust, but sucking the juices out of the leaf's 'veins.' And as they feed, they infect the vine. For years everybody thought it was a virus. Now they know it's a bacterium. And as it grows, it clogs the vine's ability to nourish all the shoots. Like a clot in our bloodstream."

It's serious, but Santoro insists this isn't 1882, when they didn't even know the disease's carrier was the sharpshooter. They didn't know that it was infectious. They didn't find out what insects transmitted it until 60 years later, in the early 1940s.

Still, Santoro's challenge is enormous. Because vines are always grafted, they can never adapt to this bacterial challenge. Like the conquistadors' colds, which killed unadapted Indians by the millions, his European vinifera grape vines have no defenses against the native Xylella fastidiosa bacterium that the native blue-green sharpshooter carries from vine to vine.

We look around for any sharpshooters, even checking the yellow sticky-paper traps at the end of each row. Nothing. It's still too cool. But Santoro says they're difficult to spot anyway: pioneers named it "sharpshooter" after the way it scoots behind a twig as soon as it sees you and looks back at you from behind its shelter.

"This particular disease is found in native vegetation," the county's Lazaneo says later. "It was here long before we [American colonizers] arrived -- or our vines. We just brought another host-plant for it to feed on."

He says native American grape vines (too acerbic-tasting for wine-making) have developed strategies for coping with the bacterium. The standard European varieties Santoro grows here -- Chardonnay, Merlot, Sangiovese, and Syrah -- never will, because (like Dolly the sheep) they are clones. Grafted plants.

Pierce's Disease used to be called "mysterious disease," "California vine disease," or, especially, "Anaheim disease." This dated from late last century when Anaheim was a retirement community for Germans from San Francisco seeking the bucolic existence they remembered from their native country. As in Germany, they planted long, narrow plots that made it easy for the breeze to help the sharpshooters travel from one vineyard to the next.

The bacterium, which may have arrived from the Gulf Coast states around the 1880s, developed a sweet deal with the blue-green sharpshooter. The mini-cicada happens to like the same sappy plants the Xylella loves to reproduce in, so the Xylella hitches a ride inside the sharpshooter's mouth. It couldn't have picked a better host. Sharpshooters fly to a zillion plants every day.

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