Grapevine Moth Spotted in Santa Clara

Pest puts 93 square miles under quarantine as California harvest begins

by Jane Firstenfeld
european grapevine moth solis winery
Within Santa Clara County's new EGVM quarantine zone, Solis Winery will press its 2010 Chardonnay wines twice to make sure the moths are nullified.
Gilroy, Calif. -- At the very last minute of a very late vintage, 39 winegrape growers in southern Santa Clara County are faced with quarantine restrictions after three European grapevine moths were trapped. The first of the third-flight generation adult males was found Sept. 15, and two more were found in close proximity within seven days, triggering the state-mandated quarantine.

The restrictions are the same as those imposed earlier this year in other California winegrape-producing counties, including Napa, Sonoma, Solano, Mendocino, Fresno, Merced and San Joaquin. Santa Clara County, south of the San Francisco Bay, harvested grapes from 1,000-plus vineyard acres in 2009, according to acting agriculture commissioner Kevin O’Day. The 620-some vineyard acres now under quarantine in the southwestern county represent about two-fifths of that production, O’Day told Wines & Vines.

Most of these are long-established, small family operations, some within the Santa Cruz Mountains AVA. Santa Clara County is a “net importer” of winegrapes, O’Day said. There is relatively little outward movement from the quarantined vineyards, so the regulations should not be too onerous for growers. The county’s ag department is working to obtain compliance agreements from all affected growers, wineries, green waste disposal facilities and transportation companies. The California Department of Food and Agriculture has set out 15 delimitation traps to further define the range of infestation.

O’Day said that the relatively late discovery of the EGVM in Santa Clara County presents a somewhat different challenge than that faced earlier in the year for other areas, because the pest will be preparing to overwinter, obscured in dormant vineyards. He said the first traps had been set in March and April. The three late discoveries may be just the tip of the iceberg. The question now is, “How big is that iceberg?” he said.

An unwelcome souvenir?
O’Day noted that Santa Clara, home to the Silicon Valley, has a high-income, cosmopolitan, multi-ethnic population. He speculated that the EVGM might have come in from international travels or care packages sent from family members abroad.

Vic Vanni, owner of 4,200-case Solis Winery in Gilroy, also termed it “likely that someone transported” the moths to the area. Because his winery within the quarantine zone uses all the grapes from its 15 vineyard acres, the only difficulty he anticipates from the quarantine is a requirement that white wines must be “double pressed” at 2 atmospheres to eliminate any larvae or eggs in the must. Fermented on their skins, red wines generate sufficient heat effectively to “pasteurize” any living residual moths. Vanni, whose only white wine is Chardonnay, said his Puleo bladder press should do the trick with limited extra labor.

Countywide, O’Day said, harvest is in general about two weeks later than normal. Some early ripening varieties and vineyards are already in. Vanni said his vineyards experienced the coolest July in about 40 years and expected his harvest to start next month, about three weeks late.

Bill Cooper, winemaker at 2,800-case Cooper-Garrod Estate Vineyards, said that although his Saratoga operation is in the northern county, and outside the current quarantine zone, “We have a high level of confidence” in the county ag department. “We’ve had invasive pests before, and the county has always responded very quickly. They will work the issue, and we’ll have a happy ending,” he said hopefully.

Commissioner O’Day, for his part, praised the local industry for its prompt cooperation. Because of the late-season discovery, there is no hope for eradication until next spring, he said. His department plans to hold educational grower meetings, probably to be scheduled after crush. Details will be posted at sccagriculture.org when available.
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