California grapegrowers are employing a variety of tactics to fight the latest pest in their vineyards—the European grapevine moth (EGVM). So far, small-scale spraying of low-impact pesticides seems to be keeping the insect under control, but as it spreads to more counties, concern remains.
The EGVM, native to southern Italy, has spread throughout Europe and to North Africa, Russia and Japan. In 2008, it was reported in Chile. The moth's first sighting in North America was in September 2009, in a Napa Valley vineyard where the pests had destroyed 10 acres of Chardonnay grapes. Since that time, the moth has been identified in seven California counties.
The moth lays its eggs on vines, and the larvae eventually burrow into grapes. The damaged fruit can attract botrytis and other molds that then may spread to healthy grapes.
The moth’s rapid spread has kick-started containment efforts by growers and agriculture officials. Experts at the University of California's Cooperative Extension have recommended spraying so-called low-impact pesticides in any and all vineyard properties located within 1,000 meters of a site where moths have been trapped. The Extension has released a list of suitable low-impact pesticides, including three approved for use in organic vineyards. The low impact sprays are not supposed to harm beneficial insects.
The appearance in California vineyards of the Australian Light Brown Apple Moth triggered aerial spraying over Monterey and Santa Cruz counties two years ago. But after some residents complained of respiratory problems, protests led the state to stop spraying. With the EGVM, the focus has been on confining spraying to agricultural properties and using pheromone-laced twist ties to disrupt moth mating cycles.
"We are within the quarantine area, so we're following the requested protocol by spraying with [the pesticide] Intrepid," said Steve Thomas, director of vineyard operations at Kunde Family Estate in Sonoma. "We'll have to tarp our trucks to haul fruit off the property, and we'll have to compost the grape skins of both our own grapes and those of any growers that come in to us." Fortunately, Thomas says he's been able to combine the Intrepid spraying with his regularly scheduled sprayings for mildew, saving on labor costs.
Growers in the quarantine area will still be allowed to move their crops to market, but they must do so in ways that keep the pest from spreading. The state recommends cleaning tractors and equipment before removing them from vineyards, and making sure grapes don't spill on the way to wineries.
Lauren Pesch, vineyard and orchard manager at Long Meadow Ranch, a certified organic property in the Napa Valley, says she has used Dipel, one of the sprays approved for use in organic vineyards. Pesch said that, to date, no moths have been found on the property, in part, she believes, because of its remote location and its elevation above the valley floor in the Mayacamas.
Pesch's father, Frank Leeds, director of vineyard operations at Long Meadow and Frog's Leap Winery in Rutherford, has been spraying Dipel at Frog's Leap. "We've not seen any sign of this insect,” Leeds said.” We're using pheromone-laced twist ties in the vineyard to disrupt mating practices should moths appear here. They've dealt with it in Europe for years and we don't want to see it get established here."