County, state join to fight moths
THE BLUE CIRCLES detail the area within 500 meters of a European grapevine moth detection, where county agricultural officials are asking residents with backyard vineyards to strip their fruit.
Courtesy of the Sonoma County Agricultural Commission
The new growth in vineyards this season means one thing to the California Department of Food and Agriculture: the threat of more European grapevine moths.
Since an infestation of the invasive moth was first detected in California in Napa in 2009, where it destroyed 10 acres of vineyards, the state agency has been working diligently to eradicate the pest through the use of quarantines, mating disruption pheromones and pesticides. The effort was largely successful at scaling back the number of moths found in commercial vineyards, but now state and county agencies are targeting backyard vines. Chief Deputy Agricultural Commissioner Lisa Correia said her department will be asking Sonoma County residents to strip the fruit from their hobby vineyards and backyard vines by the end of June, if their property is located within 500 meters of where a European grapevine moth has been detected (see map).
"It's the most effective way to control the moth," she said, "Rather than giving up their fruit, they can apply materials to the vines."
Correia explained that those wanting to continue growing their fruit can treat the vines with sprays and pheromone mating disruptors to kill any moths that make try to establish an infestation in the vines. Those interested in keeping the fruit should contact the Sonoma County Agricultural Commission's Grower Liaison Shelly Mochizuki at 565-2371 to get information about approved treatment methods.
"The next step is to do community outreach," Correia said, adding that state agriculture workers will be going door-to-door in both Napa and Sonoma county to inform residents about the need to drop their fruit or treat their vines.
The moth was first detected in Sonoma County in Kenwood in March 2010, sparking CDFA to put a section of the Valley under quarantine to restrict the movement of plant material and stem the spread of the moth. In 2010, 59 moths were discovered in traps across Sonoma County, with about a dozen detected in Sonoma Valley, including on Broadway, Denmark Street, Old Winery Road and Arnold Drive. As more moths were found, the quarantine was expanded to cover most of Sonoma Valley.
"The quarantine in Sonoma County does stretch from the very southern part of Carneros all the way to Geyserville," Correia said.
Although much of the county is under quarantine, Sonoma has seen only a small fraction of the moths found in Napa, where more than 70,000 moths were discovered between January and April of 2010. An aggressive response from commercial growers last year seems to have been effective, as only one European grapevine moth has been found in Napa and none have been found in Sonoma County in 2011.
"It's not what we're doing, it's what the growers are doing," said Steve Lyle, a spokesman for CDFA. "We did not treat the pest in Napa or Sonoma County."
In 2010, growers within 1,000 meters of a moth find were required to treat their vineyards with a pesticide spray able to kill the moth larvae. Several compounds are on the market, including some organic options. In 2011, the regulations were changed, requiring growers within 500 meters of a moth find to treat the vines with both a spray to kill the larvae and pheromone twist ties designed to prevent mature moths from finding each other to mate. Growers say there has been a significant added expense in treating the vines, but are eager to eradicate the pest.
"There's definitely an economic cost," said David Cook, proprietor of Cook Vineyard Management, which oversees five vineyards located within 500 meters of a moth find. He said the agricultural commission recommends growers spray their vineyards twice this year, and put out 200 pheromone twist ties an acre, at a cost of around $250 an acre - but added the effort is worthwhile.
"We want to eradicate this. We don't want to deal with this year after year," Cook said. "Now we need help from the local people with backyard vineyards."
Correia said CDFA has spent around $1 million trapping the moths in Sonoma County. The California Association of Winegrape Growers agreed to commit $80,000 to hire Mochizuki as the growers liaison.