A European grapevine moth has been trapped south of Healdsburg, the farthest outside the Napa Valley the invasive pest has been found, agricultural officials said Friday.
Three moths also have been trapped near Fairfield.
A spokesman for the U.S. Department of Agriculture said a quarantine will be established there, making Solano the third county in California where restrictions will be placed on growers due to the moth's presence.
About 10,000 acres of Sonoma County farmland is expected to come under quarantine due to moths trapped here and in nearby Napa County.
Earlier this week, agricultural officials confirmed that about 9,000 acres will come under two quarantines, one near Kenwood and one east of Sonoma. Another 1,000 acres near Knights Valley are expected to be quarantined due to moths found near Calistoga in Napa County.
Sonoma County Agricultural Commissioner Cathy Neville on Friday confirmed that a single moth was found south of Healdsburg and west of Windsor. A second moth must be found within three miles of the first discovery before the state will impose a quarantine there.
Meanwhile, agricultural inspectors in Napa have been finding traps loaded with the pest.
To date the state lab in Sacramento has confirmed more than 29,000 grapevine moths, said Larry Hawkins, a spokesman for the U.S. Department of Agriculture. A week ago, growers were told the number was 6,000.
Some traps are being removed from the most heavily infested area between east Napa and St. Helena, Hawkins said. Further trapping gains no new information about the infestation and inundates state lab workers. The more critical work, he said, is discovering the extent of the pest's geographical distribution.
Napa growers, meanwhile, have begun to apply pesticides to attack the moth eggs and larvae, Hawkins said. Growers have described the insecticides as low impact, including some approved for use on organic farms.
The Napa growers also are trying to disrupt mating among adult moths by using artificial pheromones designed to attract and confuse the male insects. The pheromones are injected into plastic twist ties, which are placed around the vineyards.
Grapevine moths, native to Mediterranean Europe, were first confirmed in the U.S. in September, when they were spotted in Napa Valley. They destroyed the crop in one Oakville vineyard and damaged other vineyards, state officials said.
Moth larvae burrow into and feed on the berries, often infecting the fruit with botrytis, or bunch rot.
Growers in quarantine areas can still ship their grapes to market, but they must agree to inspections or to rules that ensure that they don't help spread the moth. Those rules have yet to be formalized.
Nick Frey, president of Sonoma County Wine Grape Commission, called the new find a concern. Growers will have to take extra care when traveling between vineyards.
When a tractor arrives, Frey said, "you need to be sure it's clean, and when it leaves it will have to be cleaned again."