The European grapevine moth.
By Barry Eberling
A $59 million, six-year battle has all but eliminated a grape-maiming invasive pest that struck the heart of Napa’s wine country.
Napa County has spent $9.8 million and the wine industry $49 million fighting the European grapevine moth, the county Agricultural Commissioner’s Office reported. Money went to such things as detection, trapping, insecticides and quarantine compliance.
In addition, the U.S. Department of Agriculture spent $46.5 million fighting the moth in California. That makes for at least a $105 million statewide effort. By comparison, the Highway 12 widening in Jameson Canyon cost about $130 million.
The result: no moths have been found in Napa County since 2013.
“Hopefully about this time next year, we’ll be able to work with our state and federal partners and be able to declare eradication,” county Agricultural Commissioner Greg Clark told the Napa County Board of Supervisors.
Eradication means the federal- and state-imposed quarantine for the moth would be gone. Napa County would officially be moth-free.
But Clark doesn’t want people to become complacent. He’s not declaring victory. Signs remain posted along county roads with a photo of the European grapevine moth and the words, “Keep it on the run. Don’t let up.”
“If it’s present and we don’t know it, people might have a false sense of security,” Clark said.
European grapevine moth, AKA lobesia botrana, is a tan-brown-and-black moth about a quarter-inch long that’s native to southern Italy. Larvae feed on the inside of grapes in successive generations, hollowing them out and leaving excrement. That’s hardly a fitting image for the world-famous Napa Valley.
The moth made its first known United States appearance in 2009 amid the heart of the Napa Valley. Video shows moths swarming an Oakville vineyard in such numbers that it appears a person could wave a hand and hit a dozen.
That 11-acre block of chardonnay ended up a European grapevine moth disaster zone. Clark estimated the damage in lost crop at $150,000.
Rex Stults of Napa Valley Vintners recalled receiving an urgent call from then-Agricultural Commissioner Dave Whitmer after the first moth find had been made. He recalled Whitmer as saying the county had a really big deal on its hands that would take a broad effort to tackle.
“I remember looking at the problem that day and saying, ‘This is insurmountable,’ ” Stults told supervisors.
Bruce Phillips is managing partner at Phillips Family Farming, which grows grapes at Vine Hill Ranch west of Oakville on the slopes of the Mayacamas Mountains. He is among the hundreds of growers who faced the moth threat.
“It represented a huge risk to the industry,” Phillips said. “We’re very fortunate to have an agricultural commissioner and a level of focus that enabled us to mobilize against that threat.”
Napa County and the state and federal governments devised a battle plan.
In March 2010, the state Department of Food and Agriculture announced the creation of a 162-square-mile quarantine area mostly in Napa County to stop the insect’s spread. Grape growers and vintners would do such things as tarp truck beds transporting grapes to keep fruit from falling on the road. They would clean equipment leaving their property.
Grape growers within the ground zero used such tools as insecticides and a synthetic pheromone that keeps male moths from locating females, thus disrupting the insects’ mating.
Vine Hill Ranch remained out of the moth “hot zone,” Phillips said. Still, even though the moth didn’t migrate there, the ranch put out dispensers with the mating-disrupting pheromone.
The acres of vineyards treated for the moth fell from 22,000 in 2010 to 1,900 this year. In August 2014, the state removed 18 square miles from the quarantine area, including the Carneros area. Now the question is when the bulk of Napa Valley will be free of the quarantine.
Napa County remains under a European grapevine moth watch. Bright-orange, prism-shaped traps are deployed at a rate of 100 per square mile in rural areas and 25 per square mile in cities. More than 11,600 traps are deployed.
“We’re happy to see those little, orange triangles in our vineyard,” Yeoryios Apallas of Soda Creek Vineyards told supervisors.
The traps yielded:
—100,793 finds in 2010;
—113 in 2011;
—77 in 2012;
—40 in 2013;
Since then, not a single European grapevine moth has been found.
Although Napa County was the European grapevine moth epicenter, the moth turned up in other counties as well. Sonoma, Solano, Mendocino, Monterey, San Joaquin, Merced, Fresno, Santa Clara, Santa Cruz and Nevada counties all had moth finds.
But no moths have been found in the state this year, California Department of Food and Agriculture spokesman Steve Lyle said. One moth was detected in Cazadero, Sonoma County in 2014. All quarantines have been lifted except for portions of Napa and Sonoma counties.
A mystery remains, even as the moth appears to be on its way out.
“We never really determined how the European grapevine moth got here,” Clark said.