FRESNO — Just as Napa seems to be getting the best of a grape pest that can spoil entire crops the tiny moth has popped up in yet another wine region.
On Wednesday, state and federal agriculture officials expanded the state's quarantine area to Nevada County in the Sierra Nevada foothills after traps there detected two European grapevine moths. It's the ninth California county where the movement of plants and equipment is now tightly controlled.
The discovery of the moths 60 miles northeast of Sacramento was a setback for agriculture officials and growers who had been celebrating recent success in controlling the grape-killing pest in Napa County, where it first was detected in 2009.
Spring trapping has netted just 90 moths in Napa as of Wednesday, compared to 70,000 caught between Jan. 1 and April 1 a year earlier.
"Growers have been doing a really great job of treating and really knocking it down," said Steve Lyle, spokesman for the California Department of Food and Agriculture.
The moths feed on grape flowers and clusters as well as stone fruits and can produce three generations in a season. They spread through the regional movement of plants, fruit and equipment.
Until last month the bugs had been confined to 2,000-square-miles in Napa, Sonoma, Solano, Mendocino and Santa Clara counties as well as the San Joaquin Valley.
State agriculture officials will continue to work with homeowners inside the quarantine areas to combat the moth on private property. Officials prefer to remove fruit in the core infestation areas, but Lyle said they will spray with an organic bacterial agent if the homeowner prefers. Commercial growers are responsible for their own eradication.
Agriculture officials are unsure how the moths made their way to the Sierra foothills but suspect they must have hitchhiked on plants or fruit.
"We have a large number of wineries for the number of acres we have planted," said Jeff Pylman, county agriculture commissioner. "We have a lot of grapes going out of the county and a lot coming in."
While the eradication cost to growers in the state's premiere 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's the county's biggest crop and the fourth-largest commodity, behind cattle, irrigated pasture and rangeland.
"The success we've had in Napa gives us cause to believe that this is an infestation that we can ultimately eradicate," Lyle said.