Mrz 25

Wine Country sounds alarm over grapevine moth

Tag: Oenologie,Regionensigi.hiss @ 21:11

Peter Fimrite, Chronicle Staff Writer

Monica Cooper, Napa County's viticulture farm adviser, fi... Officials have put 162 square miles of county land under ... The discovery of the European grapevine moth in Napa Coun...

The monster that is threatening to turn premium Napa Valley wine into rotting slime was quickly plucked out from underneath the peeling bark of a grapevine.

The white cocoon containing the beast was barely large enough to cover biologist Monica Cooper’s fingertip, but its presence is no more welcome in Wine Country than pod people from outer space.

Hundreds, possibly thousands, of European grapevine moths are now emerging from cocoons in dozens of vineyards in the heart of the world famous wine-growing region. It is the first time the pest has ever been seen in North America.

„This one is in the pupal stage,“ said Cooper, Napa County’s viticulture farm adviser and the director of the UC Cooperative Extension, as she squeezed out of the fuzz a tiny brownish-green creature. „They spend the winter in a cocoon.“

The discovery of the grape-gobbling pest has mobilized vineyard owners, biologists, local, state and federal agricultural officials in a regionwide effort to stop the alien invader. The California Department of Food and Agriculture recently placed under quarantine 162 square miles of land, mostly in Napa County with parts of Sonoma and Solano counties. The idea is to hit the moth hard now as it emerges from its winter dormancy.

„My immediate goal is to make sure it doesn’t cause growers any losses this year,“ Cooper said. „It would be great on top of that if we can eradicate it or suppress it enough so that it is not a problem, but we don’t know enough yet to determine whether we can do that.“

The moth, known scientifically as Lobesia botrana, is native to southern Italy and is now found throughout Europe, North and West Africa, the Middle East and eastern Russia. Grape growers in Europe have been fighting the fruit-filching fiend for at least a century, but the insect only recently found its way to Japan and Chile, where it was introduced in 2008 on harvest equipment.

The moth sometimes feeds on other fruit crops, according to experts, but it has adapted to the life cycle of wine grapes.

The grapevine moth is the worst vineyard pest to be introduced to the Napa Valley since the dreaded vine mealybug hit in 2002. It is considered a worse threat to crops – particularly grapes – than the light brown apple moth, which has been detected throughout California but has never been found in a Napa Valley vineyard.

First detected in Oakville

The juice-sucking invader was first detected in the Oakville area of Napa County on Sept. 15, but agricultural officials believe it was present throughout the summer. One grower in Oakville lost 9 acres of grapes, his entire harvest for the year.

The moths have curiously been found on Napa Valley Cabernet Sauvignon and Merlot grapes while in Europe they are known to prefer white wine grapes.

On Wednesday, Cooper pointed out two dead moths in one of the 3,000 sticky traps placed throughout the county. The warm weather is probably helping the insects, which only fly at dusk when temperatures are at least 54 degrees Fahrenheit.

Cooper said the moths will produce three generations of offspring during the grape-growing season. The adults, which are only about a quarter of an inch, will mate and lay eggs on the vines. The caterpillars that emerge will eat the flowers. The second-generation worms burrow into the fruit, introducing a fungus that causes „bunch rot“ in grapes. The third generation crawls under the bark and pupates for the winter, she said.

The trick now, Cooper said, is to learn as much as possible about the moth, how it got here, how far it has spread and what methods will be needed to prevent it from establishing a foothold in the rest of California.

Testing to reveal origins

Nobody knows yet how the bug got to California, but genetic testing will be used to determine where it came from, a process that could take years because DNA samples will have to be collected from all the suspect countries.

Meanwhile, food and agriculture officials are placing moth traps in vineyards throughout California in an effort to see if the moth has spread.

„If the trapping shows that the infestations are only in the areas where we found them so far, then maybe we can get rid of this pest, but if they are more widespread, then that it is probably not realistic,“ said Jon Ruel, chairman of the industry issues committee for the Napa Valley Grape Growers Association.

Ruel, who is also the director of viticulture and winemaking at the 480-acre Trefechen Family Vineyard, said growers will have to be very aggressive in attacking the grape-chewing bug.

The plan is to scatter throughout the region bendable wire devices that disrupt moth mating by wafting female pheromones into the air, tricking the males into a fruitless search for sex that ultimately results in death.

Bats that eat insects and wasps whose larval offspring feast on the innards of the moths will also be used. But the most common method to attack the pest will probably involve pesticides that have been effective in Europe.

„The fact that the grapevine moth has already spread as far as it has indicates to me that this pest is very dangerous,“ said Jim Verhey, the managing director of the Silverado Wine Growers. „We as growers have to respond to this threat by working together.“ E-mail Peter Fimrite at

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