The Grape Industry’s Little Pest

California just received $17 million to battle the European grapevine moth. Is it really such a threat?


The Rutherford Grange is an old wooden building with white stucco finish, just off the well-traveled wine road of Highway 29. Adjacent to big-name vineyards, it stands as a reminder of the area’s blue-collar roots: unfussy, with a cracked wood threshold and bare light bulbs on the cement porch.

Rutherford is, today, one of the premier wine regions in the state. It’s also ground zero in the battle against a new invasive species in California called the European grapevine moth (Lobesia botrana) or EGVM. On an unseasonably hot day during the first week of February, the Grange was packed with farmers and vintners eager to hear about the state’s plan for dealing with the pest. Napa Agriculture Commissioner Dave Whitmer delivered the message.

“Right now we’ve got this thing down,” he said of the moth, “and we’ve got our foot on its throat, and now’s not the time to let up.”

The first EGVMs were discovered close to Rutherford in late 2009 and have since been confirmed in 10 counties across the state. The plan for the EGVM in California is eradication, not control. The U.S. Department of Agriculture and the California Department of Food and Agriculture (CDFA) have established quarantine zones within a five-mile radius of any two confirmed moth or larvae finds, landing most of Napa County and large parts of Sonoma County in quarantine zones.

The moth itself doesn’t cause much damage to the fruit or the vine. The larvae, however, are voracious eaters that go straight for the fruit. Late generations of larvae are actually laid in the fruit, small enough to fit several on the head of a dime, and even the most assiduous farmer might not spot them until the crop is damaged. In 2010, federal dollars poured into the Golden State to trap and monitor the pest, and this year officials are doubling their contribution to the fight, calling the situation an “emergency” for California’s agriculture, even as some farmers and vintners deny the gravity of the situation, harking back to the controversial light brown apple moth scare of 2007.

Less than a week before the community forum in Rutherford, the first moth of 2011 had been trapped. Within quarantine areas, growers have been encouraged to spray pesticides even if they never see a moth, while sticky traps along with mating disruptors and pheromone lures are set year-round. In Napa, the program has been very successful in reducing the EGVM population, but whether complete eradication is possible is not clear.

“The good thing is that they are pretty easy to control,” Whitmer says. “The chemistry [of pesticides] is pretty soft.”

The European grapevine moth was completely foreign in North America until the 2009 Napa finds. Whitmer says that at the time, no one even knew what it was. Samples were sent to the CDFA, and within 48 hours of the species confirmation officials had pheromone lures from the Department of Agriculture and 350 traps set in Napa. The actual number of moths and larvae confirmed in 2009 was low, because detection occurred at the end of the moth’s lifecycle, but that year one Oakville grower had a 100 percent crop loss on an 11-acre Chardonnay vineyard. While his name is usually left out of polite conversation, that grower has become something of a cautionary tale.

“Where we first saw the pest,” Whitmer says, “it snuck up on a really well-respected grower.”

The following spring, in 2010, Whitmer and the CDFA led a $1.26 million campaign against the moth in Napa. The number of traps increased to 8,000 in the county, and roughly 15 extra workers were hired. Close to 100,000 male moths were trapped in Napa County before summer. Sonoma County officials set 4,000 traps, hired 18 seasonal workers and captured 24 male moths before summer. The shock of first-round trapping was enormous; one year the moth didn’t exist, and the next year more than 100,000 spread around the state.

The moth doesn’t move far on its own, so controlling its movement comes down to managing the movement of grapes and equipment used in vineyards. So far, farmers have had a lot of options concerning pesticides—or, as some growers have chosen, no pesticides at all.

Despite the rapid spread of this moth across California, not everyone is convinced the state is in crisis. Phil Coturri, a 30-year grower in the area who manages about 500 acres of organic and biodynamic vineyards in Sonoma and Napa counties, says the moth is serious, but perhaps not serious enough to warrant wholesale spraying. “I’ve seen the damage it can do,” Coturri says. “It’s horrendous. But do I think they’re freaking out a little bit? Yes.”

Coturri himself spent two months in Europe recently learning about the moth, and in his own vineyards, he plants auxiliary crops such as flowers that attract predatory wasps that feed on the larvae instead of spraying pesticides. “I think we wasted a whole bunch of spray and a whole bunch of money and a whole bunch of time spraying so much last year,” he says. “I think with diligent monitoring, we can control it.”

This is where some growers and the state disagree. Steve Lyle, spokesman for the CDFA, is blunt on the topic. “It’s an invasive species that doesn’t belong in California,” he says. Eradication is the goal.

But even for conventional growers, spraying large areas for a pest that hasn’t officially appeared defies conventional wisdom. Pesticides can cost growers between $50 and $60 per acre, mating disruptors cost about $100 per acre, and for organic growers, the cost is driven up by the increased frequency of pesticide application.

Martin Mochizuki, a Napa vineyard consultant and official liaison between Napa growers and Napa officials, says some growers want to wait until they see damage to spray. But “to wait until you see the larvae is too late,” Mochizuki insists. “I know one grower who waited. When it rained, you could see it on the webbing. You could see it shining from the road.”

The CDFA received a total of $7.8 million from the Feds to conduct statewide monitoring and quarantine programs in 2010, and at the end of the year, 10 counties had confirmed EGVM populations. Eight of those counties, including Napa and Sonoma, had areas of farmland under federal quarantine.

But there was progress, also. In California there are three generations of EGVM in a year. Each succeeding generation of larvae tends to do worse damage to the fruit, and under normal conditions grows larger than the previous generation. But by the third generation last year, in the fall, fewer than 300 moths were detected in Napa and just four male moths were trapped in Sonoma County. The Oakville Chardonnay grower was able to harvest again.

Almost all of the money marked for the EGVM is what officials call “pass-through” funds, meaning it comes from the Feds, goes through the state and is distributed to the county level. On Feb. 8, the federal government announced that it would release close to $17 million in emergency funds to battle the pest in California, more than twice the budget of last year. In response, Sen. Dianne Feinstein issued a statement of thanks to Secretary of Agriculture Tom Vilsack, saying, “As you know, this dangerous and invasive pest threatens to devastate the $34.8 billion agriculture industry in my state.”

Thirty-four billion dollars represents the entire state agriculture industry, rendering the statement a little dramatic, given the moth’s discriminating palate—in California, the larvae eat grapes, and in a pinch will eat olives.

Coturri has a different take on the pest than do state and local officials. “Are we going to eradicate EVGM in vineyards?” he asks. “I don’t think so. But we can control it.”

So far, Coturri has been controlling it well without pesticides, according to his account. He says his organic and biodynamic vineyards, even the ones in quarantine zones, are completely EGVM-free.

Sonoma County Library