In what’s being heralded a “success story,” California is officially eradicated of the European grapevine moth (EGVM).
The good news means the lifting of quarantine restrictions in several grape-growing regions throughout the state.
The EGVM was first detected in a Napa County Chardonnay vineyard in 2009, the first time ever the pest was discovered in North America. Subsequent detections in the counties of Fresno, Mendocino, Merced, Nevada, Santa Clara, Santa Cruz, San Joaquin, Solano and Sonoma led to quarantine restrictions and a mass effort to determine pest numbers through trapping.
The last EGVM detection in California was June, 2014.
How the EGVM first wound up in Napa County remains a mystery.
“It is no easy feat to eradicate an invasive species, especially one like the European grapevine moth when it gains a foothold in a place as hospitable as California’s prime wine grape growing region,” said Karen Ross, Secretary of the California Department of Food and Agriculture.
Napa Valley wine grape grower Steven Moulds calls the eradication “a hard-fought victory.”
EGVM numbers quickly rose, particularly in Napa County, where trap counts in 2010 exceeded 100,000 moths from 3,800 traps blanketing the county. Quick collaboration between local agricultural officials, state and federal government agencies, and a group of international researchers including University of California wine grape specialists, helped identify the problem and recommend a course of action leading to eradication.
The EGVM, or Lobesia botrana, originates from southern Europe.
First and second generation insects feed on grape flowers and developing berries. By the third generation, larvae can cause great damage by feeding on grape berries, contaminating the fruit and exposing it to Botrytis and other infections.
Over the years, growers in the San Joaquin Valley and elsewhere outside of the Napa and Sonoma wine regions were able to quickly eliminate moth counts. As this happened, quarantines covering 2,334 square miles in 2013 fell to 446 square miles in 2014.
The Napa wine region took a mating disruption approach to eradication, while those in the San Joaquin Valley took a more direct approach by using labeled insecticides to kill the insect.
Napa County Agricultural Commissioner Greg Clark credits the collaborative effort between all parties involved, from local growers and staff in his office, to local and international university researchers, to the state and federal government, with the success achieved.
At the end of the day, Clark says the success of the eradication efforts needs to be pinned on local efforts.
“Eradication of the EGVM is an important accomplishment in itself, but this program is perhaps even more valuable as an example of what we are capable of as a community,” Clark said.