Napa Valley, Calif., grape growers, pest control advisers (PCAs), University of California entomologists and state and federal regulators have the European grapevine moth (EGVM) on the run — out of California.

Lucia Varela, UC North Coast IPM advisor in Santa Rosa, Calif., told the 39th annual California Association of Pest Control Advisers (CAPCA) conference that she is “cautiously optimistic” that a major EGVM infestation in the Napa Valley has been turned back.

She detailed some dramatic numbers to back up her optimism.

Last season 100,000 first-generation EGVM moths were trapped in the EGVM core infestation in Napa; 1,000 moths from the second generation were caught and just 250 from the third. Second- and third-generation EGVM are the most damaging.

EGVM was first identified in Napa in late 2009 where it destroyed the wine grape crop in at least one vineyard. That sparked a herculean effort in Napa around the core infestation area surrounding the towns of Oakville and Rutherford.

It has been surmised that EGVM found its way into the North Coast on plant material or machinery imported from Chile. However, Varela said federal and state regulatory officials “have not (yet) found a smoking gun.”

Acting quickly after the 2009 infestation, state and federal officials blanketed grape growing areas of the state with more than 40,000 pheromone traps to see where EGVM might have wandered from Napa.

It was identified last growing season in relatively isolated portions of nine counties and eight areas were quarantined. These quarantines are triggered by trapping two or more adult EGVM within a three-mile area during one life cycle. Fewer than 100 moths were trapped statewide outside of the Napa core infestation.

Populations trapped outside of Napa this growing season were “were very, very low,” she said.

By the end of the 2010 season, more than 2,000 square miles were under quarantine, which called for strict sanitation rules for moving product and equipment out of quarantine areas. Although trapped EGVM numbers were low, growers, UC entomologists and PCAs were recommending an aggressive control effort to prevent the establishment of a breeding population in those areas.

Ground zero, however, was Napa County.

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EGVM (lobesia botrana) is native to Southern Italy and is now found throughout Europe, North and West Africa, the Middle East and eastern Russia. It found its way to Japan and in 2008 was detected in Chile. That is where Varela, Walt Bentley, UC IPM adviser in the Central Valley and others first researched it on a trip there. What was learned there proved invaluable when EGVM invaded California high value premium North Coast vineyards.