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.

Workers spray a vineyard in Rutherford to kill the eggs and larvae of the European grapevine moth. The moth has been found in Fresno, Mendocino, Sonoma and Solano, but the biggest infestation has been found in Napa county. (Press Democrat photo)

“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.

Some growers and winery leaders doubt the moth can be eliminated from Napa, though that outcome still remains a goal of county agricultural officials. Nonetheless, they expressed confidence that they can cope with the insect just as they have met other threats, including phylloxera, orange tortrix and vine mealy bug.

“We're not going to be eradicating it,” said Michael Silacci, winemaker at Opus One winery in Oakville. “We're going to be controlling it ... You do not eradicate Mother Nature.”

Silacci sent workers Tuesday to spray an abandoned vineyard across the highway from his winery, with the owner's permission.

“It's those abandoned pockets that are going to be a problem,” Silacci said.
Growers also are emphasizing the need to routinely wash tractors and other equipment before moving them to other vineyards.

No one knows for sure how the moth arrived in Napa, though some theorize it came in on farm equipment or on illegal cuttings from Europe.

The tiny creatures, two of which can fit on an adult fingernail, are poor long-distance flyers. They have “a short fuel tank,” as Neal put it. But discoveries of the moth in other counties demonstrate its adeptness at hitchhiking to new areas and taking up residence.

Brian Tench, owner of Tench Vineyards on Silverado Trail, said he has yet to actually find a grapevine moth in his vineyard. But after the pest was trapped on either side of his 42 acres, he decided to spray anyway as a precaution.
“We're surrounded,” said Tench, walking past a pond inhabited by box turtles, goslings and a blue heron.

Other growers are just as determined to stop the moth's spread, said Tench, who first planted grapes on the property almost 40 years ago.

“I don't know of a single grower in Oakville that isn't on top of this,” he said.
In Sonoma and Mendocino counties, agricultural officials are gearing up for anticipated quarantine areas. They have been educating growers about the very practices underway in Napa, including the sanitation of grape bins and other equipment moving in and out from infested areas.

Linegar said a property owner already has agreed to remove and burn abandoned vines in a vineyard north of Ukiah where a single grapevine moth was recently found. With 28 more trapped in a nearby vineyard, Linegar said he is looking for the same kind of cooperation from wine operations that bring grapes or equipment in from Napa.

“The industry brought this pest here, and they're going to have to be the ones to step forward and do the right thing,” Linegar said.
Unlike the light brown apple moth, another foreign pest that feeds on hundreds of types of plants, the grapevine moth eventually will die off without grapes.

But with grapevines a common feature in Wine Country backyard and commercial landscapes, the fight in time may spread beyond the farms. In Chile, where the pest was found throughout the country in recent years, agricultural officials required that some home grapevines be sprayed or stripped of fruit, said Monica Cooper, a moth expert and the Napa County director for the UC Cooperative Extension.

“If eradication is your goal,” said Cooper, “you may have to do something with your backyard grapes.”