Scourge Threatens State’s Wine Producers
Maverick vintner Randall Grahm watched with dread for three years as the symptoms spread through his 30-acre vineyard. First, the edges of the leaves of his prized Santa Cruz Mountains grapevines became “scorched.” Then the fruit clusters shriveled into raisins.
Finally, he and his vineyard manager dejectedly ripped the vines out one by one and began contemplating a move from the verdant hamlet of Bonny Doon to the hot and dry Livermore Valley, east of San Francisco.
Count Grahm as the most profound sufferer to date in California’s battle against Pierce’s disease, a potentially disastrous pest-borne scourge that is sending tremors through California’s wine industry.
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Alarmed grape growers have launched an unprecedented effort with university researchers and state officials to try to control the problem--the worst to plague vineyards since a root louse known as phylloxera forced the costly replanting of thousands of wine country grapevines beginning in the late 1980s.
“Hot spots” of the devastating--and incurable--Pierce’s disease are surfacing as vintners in the Napa Valley and Sonoma County are enjoying tremendous demand for premium wines but have seen recent grape harvests squeezed by bad weather and phylloxera damage. The prospect of further reductions in yields--which could boost wine prices for consumers--has vineyard owners scurrying to find a fix.
“It’s a war,” said vineyard manager Rex Geitner, vice president of a Napa Valley task force seeking to raise funds for research.
Grape growers are not the only ones battling the first major outbreak of Pierce’s disease since the 1940s. Farmers of alfalfa, peaches and almonds are also scrambling to figure out how to hold at bay various types of sharpshooters, voracious if minuscule leaf-hopping insects that inject deadly bacteria into plants.
With new strains of the disease popping up in Brazil’s citrus fields and coffee plantations, farmers throughout the world are watching to see whether California can succeed in curbing the epidemic.
Known as Anaheim’s disease in the 1880s, when it wiped out Southern California’s flourishing grape-growing trade, Pierce’s disease has already set back North Coast vintners and growers $18 million. That is still a pittance contrasted with the $500 million or more that phylloxera has cost. But expenses related to Pierce’s disease promise to soar as farmers and gardeners statewide rip out host vegetation and replant a variety of crops and ornamental plants.
The name Pierce refers to Newton B. Pierce, California’s first professionally trained plant pathologist, who was dispatched to the state in the late 1800s as a special agent to the U.S. secretary of agriculture after Southern California grape growers pleaded for government help.
His 1892 publication on “California vine disease” characterized the problem, but Pierce, a specialist in bacterial pathogens, ironically never was able to find the true cause--a bacterium known as Xylella fastidiosa. Another entomologist named the disease for him in the 1930s.
Given the devastation that occurred in the 1880s, it is not surprising that California vineyard owners are atwitter over Pierce’s disease. The good news is that the ailment does not affect the quality or safety of wine. In infected vines, the bacteria, carried by the tiny blue-green sharpshooter, plug the system that carries water throughout the plant. The grapes wither into raisins and therefore are not harvested.
But the problem packs a double wallop for vineyard owners: There is less crop to sell, and the grower must bear the cost of replanting and forgoing a crop for three to four years before new vines mature.
“The possibilities of a major epidemic are always in the back of growers’ minds,” said Alexander H. “Sandy” Purcell, a UC Berkeley entomologist regarded as the leading authority on Pierce’s disease. “The specter of a situation such as occurs in the Gulf Coast states or coastal Los Angeles County looms as a threat.”
In those regions, Pierce’s disease has rendered commercial vineyard development futile. Even homeowners attempting to cultivate backyard crops find that the vines are soon wiped out.
The disease’s various offshoots affect plants differently, with the most severe damage occurring in grapevines, according to Purcell.
“Alfalfa dwarf” symptoms, found mostly in Southern California, take as long as a year to appear after infection. The disease reduces an alfalfa field’s productive years.
“Almond leaf scorch,” evident in Northern California and the Central Valley, does not kill the plant, but production is greatly reduced and parts of the limbs die back each year.
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A troubling new strain of the epidemic has also been spotted in Southern California oleanders, the brightly flowering ornamental shrubs that line thousands of miles of the Golden State’s highways and adorn countless private gardens.
“Oleander scorch” has also ravaged many oleanders on golf courses and estates, particularly in the Palm Springs-Indio area of Riverside County and in Orange County, where landscape managers have made the logical decision not to replant them.
The usually hardy oleanders along the state’s highways--planted to cut down on the glare from oncoming cars’ headlights--carry a value of $50 million to $100 million, according to Caltrans estimates. Caltrans is working with University of California entomologists to determine the scope of the problem and possible treatments.
Purcell also is investigating new Xylella diseases infecting citrus and coffee that are wreaking havoc in Brazil.
In Northern California’s signature wine country, the prospect of wholesale destruction of vineyards has prompted aggressive action, especially in Pierce’s disease “hot spots” that have sprung up near creeks and rivers, the sharpshooter’s favored habitat.
“It’s a terrible problem at Preston,” said John Clendenen, vineyard manager of Preston Vineyards and owner of Clendenen Vineyard Management, both in Healdsburg in Sonoma County. “It’s something we’ve learned to live with, but it makes some parcels marginally economic because of replanting.”
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In a normal year, plant diseases would force the replanting of 100 to 200 vines in Preston’s 50 acres along Dry Creek. Because of Pierce’s disease, Clendenen is replanting 800 to 1,000 vines per year in that parcel, at a cost of $10 to $12 per vine. Even in areas far from creeks and rivers, Preston has noticed significant damage.
Geitner, vineyard manager at Spring Mountain Vineyard in St. Helena, is one of many vintners using daily or weekly counts of sticky yellow traps to monitor the number of sharpshooters in the vineyards. Seven to 10 insects on a trap is considerable, but Spring Mountain has seen as many as a couple of hundred on some of its 350 traps, a figure, Geitner said, that “makes a vineyard manager shake.”
North Coast vineyard owners have been granted a permit to use a pesticide that fights systemic ailments in plants, but it can be applied only twice a year in riparian areas and vineyards. Grape growers view it as a costly, controversial stopgap measure.
Grape growers generally would prefer to control the pest in other ways. Geitner is encouraging bat populations and erecting birdhouses to attract insect-loving birds, such as swallows and bluebirds. Growers have also taken to releasing beetles and ladybugs, which eat the larvae of offending insects.
In a few cases, frustrated growers--including Robert Mondavi Inc. and Preston--have chosen to pull out particularly susceptible vines and replace them with olive trees to make boutique olive oils.
Control, said Geitner, will be “a combination of a lot of small parts. We’re trying more sustainable [farming] practices that we might not have thought of.”
No one knows why, but wineries in the Santa Cruz Mountains have seen an explosion of Pierce’s disease.
Randall Grahm and his Bonny Doon Vineyard are the biggest victims. After the 1994 vintage, he pulled out 28 acres of Syrah, Viognier, Sangiovese and other unusual varieties.
Grahm’s hillside location in Bonny Doon, 10 miles north of Santa Cruz, had been, he said, a “wonderful place to grow grapes”--until sharpshooters began munching their way through his vines, spreading Pierce’s disease.
As he watched his vines shrivel, he considered replanting, but realized that there would be no guarantee that new vines would escape unscathed. “This problem seemed almost biblical,” he said. “I took it as a serious sign.”
So after 16 years of living amid comfortable temperatures in the mid-70s, Grahm plans to move to Pleasanton, east of San Francisco. Come harvest time two years from now, he expects to be crushing grapes in scorching 100-degree days.
Nearby in the Santa Cruz Mountains at David Bruce Winery, the onset of Pierce’s disease had a different outcome. Greg Stokes, vineyard manager, pulled out the winery’s stunted 25 acres in 1992 and replanted. This year, the winery began crushing some of its new grapes.
Stokes is keeping vegetation cut back and eliminating French broom and other host plants, hoping to hold reinfection to a minimum.
“There’s no place like this area for Pinot Noir,” said Stokes, noting that the site has been farmed with vines for more than 100 years. “That’s why we’re pressing on.”
