To limit the spread of the European grapevine moth (EGVM) which was discovered in the United States for the first time last October in a Napa County vineyard, the California Department of Food and Agriculture recently established a 162-square mile quarantine, which covers parts of Napa Sonoma and Solano Counties.

It will also help free up money for state and local authorities to combat the pest, says Greg Clark, Napa County’s assistant agricultural commissioner.

“This quarantine is a formalization of something we knew was coming,” he says. “This pest is the real deal — it is a serious threat. Growers need to educate themselves about the biology of the pest, learn how to monitor and treat for it, and follow certain practices to prevent it spreading beyond their property.”

The boundaries of the quarantine area were determined by a technical working group consisting of EGVM experts from around the world, based on such factors as the biology of the insect, agricultural practices, and geography, Clark says.

Although EGVM feeds on the flowers and fruits of various plants, including blackberries, cherries, nectarines and olives, it prefers grapes. Feeding of the larvae damages the berries, attracting others pests, like fruit flies and ants. However the majority of damage is caused by fungi, which establish inside the burrows of feeding insects.

Last fall, 10 acres of grapes in one vineyard in Napa County suffered a total loss, mostly from Botrytis.

To monitor EGVM numbers, in late February, when the moths started flying following winter dormancy, the county set up 700 traps at the rate of 25 per square mile in a core. Elsewhere in the county, the state has put out 2,350 traps. An intensive statewide trapping effort is also under way.

Clark, Monica Cooper, Napa County University of California Cooperative Extension farm advisor for Napa County, and Lucia Varela, UC Cooperative Extension North Coast IPM advisor, have been conducting meetings over the winter to educate growers about the pest and control practices.

“The European grapevine moth isn’t a super bug,” Clark says. “Tools are available for growers to control it.”

Details about the quarantine and links to information about EGVM are available at www.cdfa.ca.gov/PHPPS/egvm