Participants in the roadshow also heard a discussion of the threats posed by mealybugs that carry grape leafroll disease. Kent Daane, UC biological control specialist, said the problem is less pronounced in the San Joaquin Valley than it is to the north in the Napa-Sonoma region.

One reason for that, he said, is the warmer temperatures and longer season to the south. “The cooler regions are of greater concern,” he said.

The major culprit in the mealybug gang when it comes to spread of leafroll disease, is the vine mealybug because of its many generations, Daane said. “It’s a numbers game,” he said.

Daane said crawlers can acquire the virus that produces leafroll within an hour, and they can be spread by wind, by getting on wings of birds or clothes of workers.

Different strains of the mealybug can cause different levels of damage.

Insecticides that can control the pest include Movento, Clutch, Applaud and Assail.

Participants in the roadshow also heard discussions of threats posed by nitrates to the region’s drinking water, talk of how viticulture research is funded and a discussion of weed management in organic vineyards.

Thomas Harter, Cooperative Extension specialist for groundwater hydrology, had some good news: Vineyards are among crops with the lowest nitrogen inputs.

Jean-Mari Peltier, president of the National Grape and Wine Institute, said the Specialty Crop Research Initiative, a major source of funding for the grape industry, could expire after 2012 without congressional action.

Anil Shrestha, associate professor in weed science with Fresno State University, said mechanical devices — the French plow or Bezzerides — are best for weed control. But he recommended using varying approaches of control to avoid “a change in species, a shift from broadleaf to grasses.”