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Pierce's Disease Devastates Vineyards in California's Temecula Region

Lynn Alley
Posted: September 16, 1999

Pierce's Disease, a deadly bacteria-induced vine disorder with no known cure, has hit hard in Temecula, one of California's two southernmost appellations. In the last several months, Temecula growers have lost more than 200 acres to P.D.

For more than a century, winemakers throughout California have been sporadically faced with Pierce's Disease, which is usually spread by the blue-green sharpshooter, an insect that breeds in prime vineyard sites near rivers and streams. However, this time around, P.D. is being carried by a new insect -- the glassy-winged sharpshooter, which Patrick Gleason, director of the Napa-based American Vineyard Foundation, called "the pterodactyl of sharpshooters."

This vigorous insect is capable of flying higher and farther than anything seen before in the state. Experts believe it arrived in Ventura County on nursery stock from its native southeastern United States sometime in 1990 and has since rapidly spread throughout southern California, feeding on ornamentals and agricultural plants in San Diego, Riverside, Los Angeles, San Bernardino, Ventura, Orange and Santa Barbara counties.

"If we don't lick this glassy-winged sharpshooter here and now, then three years down the road, there will be no more vines in Temecula," said John Moramarco, general manager at Callaway Vineyard & Winery, which has lost 42 of its 750 acres.

"You need to see this to believe it," said Bruce Kirkpatrick, a plant pathologist from the University of California at Davis and team leader of the American Vineyard Foundation's long-term research program for P.D. "The glassy-winged sharpshooter has appeared in Temecula in numbers that make the [carrier] population in Napa look minuscule."

Another observer, Napa County farm advisor Ed Weber, who recently toured Temecula, said, "This is overwhelming, and it scares the heck out of me."

A new outbreak of P.D. could soon threaten vineyards further north in California as the glassy-winged sharpshooter continues to spread. Alexander Purcell, an entomologist at the University of California at Berkeley, said that he had recently been presented with a specimen culled from the produce section of a local supermarket by one of his graduate students.

Steps are being taken throughout the state to address the outbreak of P.D. Riverside County recently declared a state of emergency in Temecula and allotted $125,000 in emergency funds, which were matched by the city of Temecula, to research the problem. The state legislature just passed a bill (AB1232), currently awaiting the governor's approval, to provide $2.2 million in emergency funds. And the North Coast Pierce's Disease Task Force -- a coalition of Napa, Sonoma and Mendocino area growers -- has voted to spend another $10,000 to study the problem.

To learn more about Pierce's Disease:

  • May 14, 1998
    An Old Pest Poses a New Threat to California Vineyards

  • Oct. 15, 1997
    California Governor Signs Bill to Aid Grape Growers Replanting Due to Pierce's Disease

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