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As Deadly Vine Disease Spreads, California Promises Funds to Fight It


Lynn Alley
Posted: April 4, 2000

As California vineyards face a deadly pest that could devastate the state's wine industry, the state Assembly's Appropriations Committee will take up a bill tomorrow that would provide $13.8 million in state funds over the next two years to fight Pierce's disease and the insect that spreads it.

Governor Gray Davis has already pledged his support to Senate Bill 671, which also includes plans for a wine industry match of 25 percent and a dollar-for-dollar match by the federal government. The bill, which could reach the governor's desk as early as April 13, has taken on new urgency as evidence mounts that the disease-carrying insect, the glassy-winged sharpshooter, is rapidly spreading north toward prime vineyard areas.

So far, the glassy-winged sharpshooter, which lives on a wide variety of agricultural and ornamental plants, has infested eight counties in southern California but is not believed to have reached North Coast vineyards yet.

However, in the past couple of weeks, sharpshooter eggs were found in San Luis Obispo County on a nursery shipment of magnolia trees destined for a winery in Edna Valley, and on ornamental plants sent to Alameda County, near San Francisco. In addition, old egg casings were found in Napa County, though experts believe the insects hatched before the plants arrived there. The discoveries resulted from a new nursery inspection program, known as the "blue-tag" system, which is being carried out by state nurseries and agricultural officials.

"We have not yet, at this point, found any live eggs or insects in Napa County," said Napa County farm advisor Ed Weber. "The bad news is that as we expected, the insects are moving north. The good news is that the blue-tag system is in place, and it's working."

The glassy-winged sharpshooter carries the bacterium Xyllela fastidiosa, which attacks plant tissue that transports water, killing infected grapevines within three to five years. There is no known cure for P.D.; the only solution is to rip up the infected vines and replant them.

While the bacteria can be transmitted by a variety of insects, the glassy-winged sharpshooter has spread P.D. with devastating rapidity because it can fly farther than other disease carriers. The glassy-winged sharpshooter first arrived in California on ornamental nursery stock shipped from the insect's native southeastern United States to Ventura County in the late 1980s. It then spread throughout southern California during the following decade.

In 1999, the alarm was sounded in the viticultural community when more than 500 acres of the Temecula Valley's 3,000 acres of vines were destroyed in just a few months.

Concerned growers, spearheaded by Corky Roche of Roche Vineyard Management in Salinas, have since enlisted the help of the state's ornamental nursery associations to control the spread of the insect from southern California to Central and North Coast appellations, and county agricultural commissioners are instituting the blue-tag program for plant inspections.

Nurseries in infested counties must now fill out a blue tag when shipping plants that can host the glassy-winged sharpshooter to unaffected counties. When a blue-tagged shipment arrives at its destination, nursery staff must arrange for the county agricultural commissioner's office to inspect the shipment before it can be sold.

When an infested shipment is identified, agricultural agents and nursery owners have three options: They can return the infested shipment to its point of origin; they can destroy the entire shipment; or they can treat it with appropriate insecticides, and then release it to the public.

According to Corky Roche, return of infested nursery stock will ensure that "the entire nursery industry will quickly get the message."

The monitoring efforts have already shown results, including the late March discoveries of viable sharpshooter eggs in San Luis Obispo County and Alameda County, as well as the old egg casings found in Napa County.

In addition to the new state funding and the inspection program, efforts are continuing to support research into a cure for P.D. At a March 23 meeting in Sacramento with members of the wine industry, Governor Davis not only promised his support for the $13.8 million in state funding, he also announced the approval of five major research proposals funded under a bill he signed last year.

The studies will examine how P.D. is transmitted, look at ways to rein in the sharpshooter and test biological controls for the disease itself, such as bacteria that may inhibit it, antibacterial agents and genetic resistance.

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Learn more about Pierce's disease in California:

  • Feb. 25, 2000
    Deadly Vine Disease in California Draws Congressional Attention

  • Feb. 14, 2000
    California Growers Battle Carrier of Pierce's Disease

  • Oct. 13, 1999
    New Pierce's Disease Carrier Spreads to Lodi

  • Sept. 16, 1999
    Pierce's Disease Devastates Vineyards in California's Temecula Region

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

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