March 10 (Bloomberg) — California grape growers have a new threat to deal with this spring, in addition to perennial concerns about frost and heat: The European grapevine moth has invaded Napa Valley, one of the top U.S. wine-producing regions.

More than 160 square miles (414 square kilometers) have been quarantined, including parts of Napa, Sonoma and Solano counties, after larvae from the non-native moth were discovered, the California Department of Food and Agriculture said yesterday in a statement.

The larvae were found in September near Oakville, about 60 miles (100 kilometers) north of San Francisco, the department said. It’s the first time the species, which is native to Europe and found in Asia, North Africa, the Caucasus and South America, was discovered in the U.S., according to the department.

“People need to be real vigilant and real committed to doing everything that needs to be done to get rid of it,” said Greg Clark, Napa’s assistant agricultural commissioner.
The exact rules for moving equipment and grapes out of quarantined areas haven’t yet been decided, he said, though they will likely involve power washing and sterilizing some items.

The larvae typically emerge in the spring, when the vines flower, and then feed on grape buds and flowers, potentially preventing grapes from growing and reducing the overall crop yield. Later generations of larvae enter the formed grapes and can expose them to rot and fungus, Clark said.
One grape farmer lost his entire crop last year, according to the Food and Agriculture department.

“People are concerned every time a pest comes in,” said Terry Hall, spokesman for the Napa Valley Vintners, which represents 375 wineries. He estimated Napa’s grape crop to be worth about $473 million. “It’s something you really have to respond to.”

— Editors: Stephen West, Jonathan Thaw.

To contact the reporter on this story: Ryan Flinn in San Francisco at rflinn@bloomberg.net

To contact the editor responsible for this story: Jonathan Thaw at jthaw@bloomberg.net