Posted: Thursday, June 09, 2011 12:00 PM
Courtesy of AgroAtlas
Lobesia botrana - European grapevine moth. Adult with brown forewings that have distinctive pattern composed of light cross-section strips with yellowish and metal dark blue spots; wingspan 11-15 mm.
Nevada County home to 'large number of wineries'
By TIM HEARDEN
GRASS VALLEY, Calif. -- The discovery of European grapevine moths in two traps near here isn't a signal that quarantines in other parts of California aren't working, a state spokesman said.
State and federal agriculture officials on June 1 declared a 103-square-mile quarantine in the Sierra Nevada foothills to contain the pest, which feeds on grape flowers and clusters as well as stone fruits.
The measures come as ag officials and growers have found success in controlling the plant killer in Napa County, where it was first detected in 2009.
Until the discoveries in Nevada County, the bugs had been confined to 2,000 square miles in Napa, Sonoma, Solano, Mendocino and Santa Clara counties as well as in the San Joaquin Valley.
The movement of the pest came "in spite of our best efforts," said Steve Lyle, spokesman for the California Department of Food and Agriculture.
"We don't know for certain that the source of the introduction came from a quarantined county," Lyle said. "The pest could exist someplace where we haven't trapped it yet, and the introduction could have been independent of a quarantined county. We don't know that yet."
Lyle said that "sometimes movement of plants means movement of pests, and that is likely what occurred here."
"We have a large number of wineries for the number of acres we have planted," Nevada County agriculture commissioner Jeff Pylman said. "We have a lot of grapes going out of the county and a lot coming in."
Under a quarantine, growers must sign compliance agreements that spell out specific measures they'll take to prevent the spread of the pest, such as making sure equipment used in the vineyard is thoroughly cleaned year-round, Lyle said. Green waste from the vineyard must be disposed of properly, he said.
In order for the grower to move product, the harvester, hauler and receiver also must be under compliance agreements, which Lyle described as a "complex system of safeguards."
Homeowners in a quarantined region face regulations, too. If they have stone fruit or grapes on their property, the fruit must be consumed on site and not moved off the property.
State agriculture officials will work with homeowners in the area to combat the moth on private property. Lyle said they will spray with an organic bacterial agent if the homeowner prefers.
The combination of spraying and a quarantine appears to be working in Napa County, where spring trapping had netted just 90 moths as of June 1 compared to 70,000 caught between Jan. 1 and April 1 a year earlier.
While the eradication cost to growers in the state's premier wine growing region has been in the millions of dollars, the value of Nevada County's 400-acre wine crop is just $1.4 million. Still, it is the county's biggest crop and the fourth-largest commodity, behind cattle, irrigated pasture and rangeland.
The Associated Press contributed to this report.