Local grape growers took comfort Friday that only one European grapevine moth has been found in Sonoma County, but were alarmed to learn that 6,000 such pests have been trapped just over the hill in Napa Valley.

"I found that appalling," said Tim Reuling, a Forestville grape grower who gathered with 260 other farmers and grape industry leaders in Santa Rosa.

The growers learned Friday that the grapevine moth likely has been in Napa for a few seasons, and that the state quarantine area adopted in March will soon nearly double in size to cover 300 square miles.

"This one's scarier than the other ones," Calistoga grower Ken Piters said of the various pests Wine Country farmers have faced in recent years. His vineyard could come under quarantine once state officials fix the new boundaries.

The grapevine moth, native to Mediterranean Europe, was first confirmed in the U.S. last September in the Napa Valley.

The pest destroyed the crop of one Napa vineyard and damaged other vineyards, a state official said Friday. The moth attacks the berries and can infect them with botrytis, or bunch rot.

The state established the first Napa quarantine in an effort to contain the moth. The quarantine rules are not yet final, but they likely will allow the transport of grapes if growers demonstrate they will take steps to prevent the spread of the insect.

Two weeks ago a single moth was found in an agricultural area near Kenwood. State inspectors have increased traps in that area and made daily inspections. But to date no new pests have been found.

"This is good news, and I'm just keeping my fingers crossed," county Agricultural Commissioner Cathy Neville told growers.

Under state and federal rules, a single moth doesn't trigger a quarantine.

The 6,000 moths found in Napa is more than 10 times the number of light brown apple moths that have been trapped in Sonoma and Napa counties in the past two years. The apple moth is an invasive pest from Australia that was first confirmed in California in 2007.

Larry Hawkins, a U.S. Department of Agriculture spokesman, said the higher number is partly reflective of intensive trapping in Napa and the grapevine moth doesn't appear to spread as rapidly as the apple moth, Hawkins said.

On Friday many growers peered into a microscope to see for themselves two grapevine moths, their wings adorned as with military desert camouflage. The tiny insects could fit together on one adult fingernail.

John Hooper, an official with the California Department of Food and Agriculture, told the growers that the moth may have been in Napa as early as 2007.

This year the state placed 25,000 grapevine moth traps around California, including 7,000 near Northern California Wine Country. Officials said those traps will reveal the extent of the moth infestation.

Napa growers soon will begin using pesticides on about 450 vineyards and other properties in an effort to eradicate the moth, Hooper said.

He expressed concern that environmental groups might object to the eradication program for the grapevine moth as they have done regarding the state's efforts to combat the apple moth.

Nan Wishner, a spokesman for Stop the Spray East Bay, said she was still gathering information, but the pesticides under discussion for grapevine moth sound relative low impact and approved for organic farming.

While pesticides can affect farmworkers she said, to date the eradication plans for the grapevine moth have been much less vast than the aerial spraying of artificial pheromones for mating disruption conducted near Monterey and Santa Cruz for the apple moth.

"No one is talking about spraying communities," Wishner said.

The large turnout at the Santa Rosa Veterans Memorial Building Friday signaled that growers take seriously the threat the moth poses to their industry. But questions still remain.

Some growers noted that grape growers throughout southern Europe have learned to live with the moth. Others voiced are worried that the pest will get established here.

"The light brown apple moth we can live with," said Wayne Hunnicutt, a grower in Freestone. "This you can't because it will destroy your whole vineyard."