Napa County’s 575-square-mile European grapevine moth (EGVM) quarantine area will remain in effect for this coming season, but the University of California viticulture farm advisor for the county is optimistic that the effort to eradicate the pest will eventually get the quarantine lifted.

Monica Cooper, University of California Cooperative Extension viticulture farm advisor in Napa County, highlighted the efforts that have worked to dramatically reduce EGVM populations at a breakout session of the California Association of Pest Control Advisers (CAPCA) conference.

More than 1,200 miles in Napa, Sonoma, Solano, Santa Clara, Santa Cruz and Nevada counties remain under EGVM quarantine restrictions. The area in Napa is the largest. That is where EGVM was first discovered in September 2009.

Soon after the first discover of EGVM in the U.S., state and federal agencies quickly ramped up an eradication effort that has already proved successful in four California counties, Fresno, Mendocino, Merced, and San Joaquin, where EGVM was initially trapped. These counties were removed from quarantine restrictions last March after quarantine restrictions were successful.

Cooper said the highly organized, multi-pronged approach that included trapping, education targeting growers and backyard farmers, spraying, mating disruption and quickly reduced the population.

She said the keys to lifting the quarantine next season will continue to be communication and education; meetings with growers and public and non-profit organizations to help people understand the urgency of control and the economic losses.

She also conducted outreach efforts to homeowners whose vines could harbor the pest.

Cooper also used a newsletter to share timely information. She now has more than 900 subscribers.

Cooper, who started her new farm advisor job just five months prior to EGVM’s emergence, said she had to quickly learn everything about this new danger to agriculture.

“Some people wonder what they’re going to work on, but this new development made that decision easy,” she said. “It was pretty much determined when 25,000 acres are affected.”

Grapes are considered a preferred EGVM host and with other California crops such as olives, kiwi and pomegranates at risk, it’s imperative to stay focused on continuing the suppression efforts to obtain a successful conclusion, she says.

While Cooper noted that EGVM feeds on the flowers of other crops, she said the damage is done by the pest’s feeding during the developmental stages of grapes. The first generation larvae feed on the grape flower clusters during May and June followed by the next generation hollowing out the green berries during July and August. During late summer the third generation causes extensive damage through webbing and feeding inside berries and within the maturing bunches. She added that the feeding damage to berries also exposes them to additional infection by Botrytis and other fungi.

To read Cooper’s EVGM newsletter, go to