Screening out grapevine virus spares Napa-Sonoma more than $60 million a year

Grapevine leafroll disease causes the plant's leaves to redden
and roll under at the edges. (Kate Binzen Fuller/UC Davis)

Providing disease-free grapevines and rootstock to California’s North Coast wine region is more than a good idea — it saves the industry more than $60 million annually, according to researchers at the University of California, Davis.

The findings were reported in a working paper released by the Center for Wine Economics at UC Davis’ Robert Mondavi Institute for Wine and Food Science. The complete paper is available online.

“This analysis places a dollar value on the efforts to prevent the spread of just a single disease in a single grape-growing region,” said Kate Binzen Fuller, the study’s lead author and a postdoctoral scholar in the Department of Agricultural and Resource Economics and Foundation Plant Services at UC Davis. “The overall benefits of such testing and certification are, in fact, dramatically higher.”

Even if growers have to pay a premium for certified, virus-free vines, the study shows that the benefits are between six and 10 times the cost.

Viral threat to grapevines

Viruses and related disease-causing microbes pose a serious threat to agriculture because there are no effective controls available to growers, other than destroying infected plants. In the case of grapevines, viruses typically spread over long distances through the movement of infected plants or the use of infected cuttings and rootstock for propagating new plants.

To prevent the introduction and spread of such viruses in grapevines, several clean-plant centers have been established throughout the United States, in partnership with the U.S. Department of Agriculture, to provide a large inventory of virus-screened plants to agricultural nurseries and growers.

The researchers found that the average annual benefit to a grower from replacing diseased vines in a vineyard was 39 cents per vine or $512 per acre, if noncertified vines or rootstocks were used in both the initial and replacement plantings. The benefit for replanting diseased vines climbed to 55 cents per vine or $727 per acre if certified plant material was used to both plant and replant the vineyard.

Overall, the researchers estimate that, for just grapevine leafroll-3 virus, the vine certification program yields a benefit of between 30 cents and 47 cents per vine, or between $401 and $616 per acre. If all growers in the region were to use certified planting stock, this would translate to a benefit of between $40.4 and $61.8 million per year for the North Coast region. This benefit translates to between 4.8 percent and 7.4 percent of the wine grape revenue for that region.