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Phylloxera Threat to Growers Feared by Some, Downplayed by Others


Grape growers in Napa and Sonoma counties are monitoring a new strain of phylloxera to see if it has the potential to become as much of a problem to the California wine industry as it was worldwide 100 years ago, when it caused major devastation.

The phylloxera is a root louse that attacks grapevines and slowly destroys them. In the 1880s, a huge infestation nearly wiped out vineyards throughout the European continent and only the discovery that there were rootstocks that resisted the pest halted its spread.

The wide use of phylloxera-resistant rootstocks, particularly a type designated AXR-1, seemed to wipe out the threat of phylloxera in California, but in 1981 the tiny pest was discovered in Monterey, Napa and Sonoma counties. Since then, it has been watched by experts who recently discovered a new strain of phylloxera, known as "Biotype B," that attacks vines grafted onto AXR-1.

This led the University of California to set up a Phylloxera Task Force to study the problem. And although early data are scanty and inconclusive, the university this month sent out a notice to growers and nurseries against the use of AXR-1 rootstocks and recommending instead eight other varieties of rootstock, none of which are in wide supply.

Dr. James Wolpert, head of the task force, acknowledged that information thus far compiled is not conclusive evidence that the Biotype B phylloxera is a true threat to the industry, but he said that phylloxera is known to triple in population each year, meaning that it spreads so rapidly that it could turn into a threat.

However, Wolpert said some reports have blown the threat out of proportion and made it seem as if the industry faced instant devastation. Thus far, less than 100 acres of vineyard in Napa and Sonoma counties--which between them have about 63,000 acres of vines--are known to have Biotype B phylloxera.

A number of major grape growers and nursery owners are skeptical that the phylloxera problem is cause for alarm, according to Rich Kunde, owner of Sonoma Grapevines, the nation's largest producer of grafted grapevines.

"I don't think it's that serious," said Kunde. "When you consider the problems we have with fan leaf virus, Pierce's disease eutypa, and nematodes, which a lot of people feel are worse problems, I don't think phylloxera is that great a threat."

Even Wolpert wasn't prepared to state categorically that the phylloxera issue was one of monumental proportions.

"We have a limited amount of data right now, and what we don't know yet is what risk we are facing," said Wolpert. "A hundred years ago, it spread with a certain rate, and what we want to know is: at what rate is it spreading, and is the risk today the same risk that the industry faced 100 years ago?"

Ironically, Wolpert said, there is a possibility that the new phylloxera infestation, even if it proves to be more widespread than now believed, could be a blessing in the long run.

"You could say there is a glimmer of hope in all this," he said. "People are replanting a certain portion of their vineyards every year anyway, and as we know more about the new trellising systems and canopy management, this (phylloxera) may encourage them to take advantage of some of these new methods of growing vines, and what we may end up with is a better situation than we had before."

Moreover, Kunde noted that a number of growers simply don't believe the threat is worth worrying about.

"This morning alone I sold 6,000 AXR rootings, and the growers know of the university's recommendations," said Kunde. "But they tell me they have lived with it (phylloxera), and they know how AXR reacts and they are not scared at all. In terms of tonnage and quality, you can't beat AXR.

"One grower told me, 'I might lose my vineyard earlier than I should, but no one's proven that yet, and I'll have all that tonnage for the years that I have my vineyard.'

"Also, I think it's wise not to plant an entire vineyard with one rootstock anyway, so some AXR is still being planted."

Wolpert, however, voiced a cautionary note against talk that phylloxera is not a major problem: "We still don't have enough data, but we know that by the time 1/2% of your vineyard is infested, you're halfway to being dead."

Two organizations have set up toll-free telephone numbers that offer information on wine.

The Washington-based National Wine Coalition said its toll-free telephone number, which started last week, will have a recorded message from prominent wine makers on the uses of wine. The first one features Robert Mondavi speaking about wine with holiday celebrations.

The Coalition's message telephone number is (800) 283-WINE (283-9463).

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