Vineyard owners across California are on their guard after a potentially devastating moth was found at several sites in the Napa Valley.

The European Grapevine Moth, never previously known in the US, destroyed the entire harvest of a grape grower in the Oakville area last year, and has now been found at several other sites near Napa City and between Oakville, Rutherford and St Helena – prime Napa Valley vineyard land.

In response, the California Department of Food and Agriculture (CDFA) has established a quarantine zone of 162 square miles, including parts of Napa, Sonoma and Solano counties.

That means severe restrictions on the way that plants and fruit – including grapes and other crops – are handled and shipped in the affected areas.

'Grapes are our state's top crop,' said CDFA secretary A G Kawamura. 'This quarantine will help us ensure that the infestation doesn’t have an opportunity to spread.'

However, the CDFA is working with the US Department of Agriculture and county agricultural commissioners to see if the moth has already spread to other parts of California.

Larvae of the European Grapevine Moth, or lobesia botrana, feed on grape bud clusters or flowers in early spring, potentially restricting yields. If the moths take hold, third generation larvae feed on multiple ripening grapes and leave them open to the risk of rot.

News item from Imbibe.com, 12-03-2010 (updated 16-03-2010)