This is the second year that the European Grapevine moth has been found in California, putting grapes, the top crop in the state—with $3.9 billion in annual gross production revenue—at risk in six counties. Napa County, where the $462 million grape crop commands the highest prices in the nation, has by far the greatest infestation. Now thousands of acres from Mendocino to Monterey have been quarantined and the federal government has announced $1 million in contingency funds to help nip this moth in the bud.
Native to the Mediterranean, the European Grapevine moth (Lobesia botrana) has been found in southern Russia, Japan, the Middle East, Chile, and northern and western Africa. How the moth arrived here is still a mystery; some experts theorize that it could have been brought in from illegal cuttings from Europe, although others think that it has been in the state for several years and we’re just now seeing an infestation. Considered a poor flyer, the moth might be hitchhiking its way around the state on trucks and farm equipment, further spreading its reach. Federal and state researchers are racing to find eradication options for the moth, whose larvae feed on grape flowers and developing fruit. Later generations eat mature grapes, predisposing the crop to fungal infections.

The California Department of Food & Agriculture (CDFA) and the U.S. Department of Agriculture (USDA) are working on an intensive statewide trapping effort to determine whether the moth has infested other areas of the state. According to CDFA Secretary A.G. Kawamura, more than 40,000 traps have been set statewide. In Napa County alone, some 50,000 moths have already been trapped. CDFA inspectors are also working with growers, nurseries, landscapers and others who handle plants and fruit to guard against further spread by regulating the harvest, shipping, and handling of affected crops and plants. In addition, the International Technical Working Group for the European Grapevine moth recently issued its recommendations for eradication.

Growers are already treating crops with what U.C. Extension experts characterize as low toxicity pesticides. CDFA has also approved two organic materials and CCOF, which provides organic certification to growers, has approved ISO-Mate EGVM, a pheromone treatment used to confuse adult male moths in search of a mate. Dr. Monica L. Cooper, the Viticulture Farm Advisor at U.C. Extension in Napa County, said that it’s unclear how well one treatment will work compared to another, though several ongoing trials will provide these data down the road.

With an estimated retail value last year of $17.9 billion, the California wine trade has reason to be concerned. “We are working with the State and federal governments and industry leaders from around the world on a plan for ensuring that this destructive pest does not get a long term foothold in Napa County or any other part of California,” said Elizabeth Emmett at the Napa County Agricultural Commissioner’s office. “At this moment, the financial impacts are related to the treatment, of course. Assuming the treatments do their job and we are able to substantially decrease or eradicate the moth, that would greatly decrease any potential crop losses.”

Jon Ruel, Vice President of the Napa Valley Grapegrowers and Director of Vineyards and Winemaking at Trefethen, doesn’t see the moth as a direct threat to wine sales, but more as a threat to the production of wine grapes. “It’s possible that higher farming costs could translate to higher bottle prices, but with so many other factors at play, including the current economic climate, I don’t see wineries raising their prices any time soon.” Ruel noted that Napa growers are still very concerned about the moth because, if left unchecked, it could impact both the quality and quantity of the grapes produced. He’s hopeful controls can be obtained without sacrificing commitment to sustainability.

Organic and Biodynamic growers are worried about the long term sustainability of their practices in the face of forced spraying to combat the spread of, or damage from, the moth. According to Josh Metz, general manager at Magnanimus Wines, moth movements from one infested location to another are facilitated by the continuous habitat which is a common feature of conventional mono-cultural farms. Metz noted that Biodynamic farms–which promote biodiversity by planting habitat breaks and multiple productive crop types–while not eliminating the risk of moth infestation, contribute to a lowered probability of infestation.

Glenn McGourty, a Mendocino viticulture and plant science advisor, said that the Agriculture Commissioner there is very sensitive to the needs of organic and Biodynamic winegrowers and will do whatever he can to insure that these growers won’t have their certification status compromised by being required to allow unauthorized insecticides applied to their crops. Metz noted that while the grapevine moth infestation presents immediate challenges to the winegrowing community, it also highlights potential limitations of certification programs designed with limited flexibility to address modern challenges, and suggests the need for continued review and revision of these programs as the nature of the agricultural landscape continues to evolve.