Unconfirmed sightings of the bug in the Santa Maria Valley and other areas of Santa Barbara County have growers there squirming. There is no known cure for P.D. -- other than replacing dead vines with new ones, which can then be infected themselves -- and no effective way to control the glassy-winged sharpshooter at this time.
"Never in the history of viticulture has there been such a threat," said Corky Roche of Roche Vineyard Consulting in Monterey County, who recently toured Temecula. "If this pest becomes established and we can't fight it, it's all over for the wine industry in California."
Although California grapegrowers have fought P.D. on and off for the past century, the vigorous glassy-winged sharpshooter flies higher and farther than any of the common carrier insects found in vineyards in the Napa, Sonoma, Mendocino and Central Coast appellations. Native to the southeastern United States, the sharpshooter can live in numerous habitats -- including prime vineyard land.
So far, more than 500 acres of the 3,000-acre Temecula appellation have been devastated, "with at least a 50 percent infection rate of the remaining vines," according to Kathy Charles, director of the Temecula Valley Growers' Association. The region's vines have been dying without even showing warning symptoms.
Though growers in southern California are on heightened alert, the reaction elsewhere in the state has been more subdued. "Most growers in the Central and North Coast appellations have no idea what [the glassy-winged sharpshooter] is capable of doing," said Roche. "They take the attitude that they've dealt with Pierce's Disease before; it's an annoyance and a killer, but it's nothing new. They have no idea that this is not the P.D. they've known and faced before.
"This is not a Temecula problem, but a dangerous threat to the California wine industry," Roche continued. "We need to pool the resources of the entire industry to do whatever it takes to beat this thing."
To learn more about Pierce's Disease: