Napa, Calif. -- Napa County Agricultural Commissioner Dave Whitmer sent a message to local grapegrowers, wineries and other stakeholders summarizing progress against the destructive European grapevine moth (EVGM). “The situation today is quite different than it was only months ago,” Whitmer wrote.

This is good news for the wine industry both in and outside of Napa County, thanks largely to concerted efforts by local, state and federal government agencies and enthusiastic cooperation from the industry itself.

EGVM populations, Whitmer said, “were very high in some vineyards during the 2009 harvest.” He termed it likely that EGVM had spread from the first infested areas to other locations within and outside the county, “before we established regulatory controls and initiated an aggressive pest management strategy.”

Early this spring, adult first-generation moths were very high in localized areas of the county, but not elsewhere. In collaboration with the California Department of Food and Agriculture (CDFA), after these adult moths were delimited, egg laying and larval hatch were targeted, and pheromone mating disruption with Isomate-EGVM was initiated in infested vineyards.

“The treatment efforts have been very successful by any measure, significantly reducing populations in the second generation,” Whitmer stated.

While the mating disruption may have reduced the efficacy of detection trapping somewhat, he continued, “This could not account for the reduction from 100,509 to approximately 1,300 moths trapped in the first and second generations respectively. And though we have not completed the third generation adult flight, the numbers continue their decline with only a few detections over the past several weeks.”

Whitmer credited the Napa County wine industry and its associations with “full cooperation and support. “The industry has stepped up to do the treatments, and the cooperation has been tremendous,” he said. But vigilance, and compliance with quarantine regulations already in force, remain mandatory through and beyond the upcoming harvest.

Critical concerns, according to Whitmer, are “movement of equipment (bins, machinery, harvesters, etc.) and trellis materials (end-posts, grape stakes, wire, etc.), and the movement of the fruit of the grape.” Napa County has issued more than 700 compliance agreements to date.

“I am confident that the regulatory program we have developed with CDFA has effectively identified the important risks and is one that will effectively mitigate the movement of EGVM. With the public expenditures and industry commitment and expense (which is extensive) to treat for EGVM, there is obviously great incentive to prevent the spread of EGVM within Napa County as well as outside of Napa County. All of us involved in this effort are committed to do our best to prevent the spread of EGVM anywhere.”

Whitmer reported, “As the scope of the infestation became clear, we also worked closely with other affected county agricultural commissioners to develop and implement appropriate risk-based measures to avoid the spread of EGVM.”

Indeed, throughout the year, EGVM has spread to -- or been discovered in -- many of the most productive winegrape-growing regions in Northern California . Today, the CDFA officially announced the expansion of EGVM quarantine to San Joaquin County, where 96 square miles bring the statewide total to 1,995 square miles under quarantine. Find a map of the restricted San Joaquin area here .

As in Napa and other previously affected areas, “The quarantine primarily affects farmers as well as those who harvest, transport and otherwise process or handle crops. These business people generally sign compliance agreements that indicate how crops, vehicles, equipment and related articles are to be treated during the quarantine,” according to the CDFA. For specifics, see cdfa.ca.gov.

What next? Back in Napa, Greg Clark, assistant agricultural commissioner, told Wines & Vines, “EVGM has proven to be a very serious and significant pest, evidenced by the damage to last year’s crop. This is not a fight we’re going to win this year.” He acknowledged that industry stakeholders and government agencies “have done a spectacular job in addressing this threat,” and termed this very good news, but cautioned, “We need to temper that with diligence that will carry over into next year.”

He hoped that in 2011, the focus would be drilled down from all of Napa County to specific properties, to continue reductions in EVGM population. “We don’t want any EVGM,” he emphasized.

Clark said that existing quarantine requirements will remain in place 365 days a year, including restricted removal of pruning materials, cleaning and movement of equipment under compliant conditions. He suggested that the multi-disciplinary EVGM technical working group will provide recommendations for growers regarding what do in the vineyards between now and spring to maintain and increase control of the pest.ShareThis