With thousands of tiny moths already trapped in budding vineyards, Napa Valley grape growers have begun spraying pesticides against the latest threat to California's premiere wine region.
"We're in the hotbed," vineyard manager Michael Neal said of Oakville, the viticulture area south of St. Helena where the European grapevine moth first appeared in the U.S.
By the time government officials confirmed their existence there last September, grapevine moths had destroyed the crop in one Oakville vineyard and caused losses at several others. Since then farm inspectors trapped more than 29,000 moths in Napa County before removing some traps from the more-infested areas to give overworked lab technicians a break.
Small numbers of the grapevine moth, native to Mediterranean Europe, this spring also have appeared in Sonoma, Mendocino, Solano and Fresno counties. On Thursday, Sonoma County Agricultural Commissioner Cathy Neville announced that a single moth also had been found in a residential area of Healdsburg.
But Napa County, where the $462 million grape crop commands the highest prices in the nation, has by far the greatest infestation.
State officials estimate that at least 300 square miles of Napa County will be quarantined this year. Affected growers will still be able to move their crops to wineries, but they must follow rules to make sure that they don't spread the pest.
To date the campaign against the moth has been waged exclusively on farmlands, and has drawn no opposition from environmentalists. But the insects have been found within the city of Napa, and eventually Wine Country residents with backyard grapes or home winemaking operations also may be enlisted in efforts to eradicate the invader.
In Oakville, an area that includes such iconic Napa wineries as Robert Mondavi, it's common to see tractors spraying the vineyards with chemicals to prevent mildew and other diseases. This spring, farmers say they also must spray with pesticides or their grapes could be ruined.
"If you do nothing, you may not pick your grapes," said Neal, who watched as one of his workers drove a tractor that sent two fountains of spray onto vines. This spring as he sprays all 700 acres he manages with a chemical to fight mildew, he'll add pesticides such as Intrepid for conventional vineyards or Entrust for organic vineyards.
The UC Cooperative Extension said those pesticides have "low" toxicity to bees, tiny parasites that attack the moth and other insects that eat grapes.