The discovery of three European grapevine moth has forced a
93-square-mile quarantine of grapes in South County. All bulk
grapes, harvest bins and equipment may not leave the quarantined
area after the Santa Clara County agricultural commissioner
announced an eradication plan today.
The discovery of three European grapevine moths has forced a 93-square-mile quarantine of grapes in South County.
All bulk grapes, harvest bins and equipment must follow rules for leaving the quarantined area after the Santa Clara County agricultural commissioner announced the quarantine and eradication plan Thursday afternoon.
The moths were found near Watsonville Road, north of Day Road and are third generation adult moths, which could become the most damaging version – as worms – if they become active in the springtime. Now and into the winter they will go dormant, but in the spring they will feed on ripening grapes and expose them to further damage through fungal infections. The moths can cause the grapes to brown and rot and can ruin an entire crop if they reproduce and spread.
“This is an extremely small number of pests. We are fortunate it’s confined to a small area,” said Kevin O’Day, the county’s acting agriculture commissioner.
The inspection will be most intrusive to grape growers at the epicenter of the discovery – including Jason-Stephens Winery and Rancho de Solis Winery – as well as residential growers within 400 meters of the epicenter of the infestation or about 10 to 20 residents, according to O’Day.
“(Monday) we’re contacting the homeowners of the area and asking if they would allow us to remove the fruit and dispose of it at a landfill,” O’Day said. He said traps are already being set around South County called “delimitation trapping” to determine how large the infestation may be and to eradicate the pests before the spring.
California tops the list in the nation of grape growers, and in 2009, the grape harvest was worth $2.74 billion – about a third of which was produced in the Napa Valley.
In South County, grapes are the eighth top-selling crop. Wine production in Santa Clara County in 2009 was worth $6.98 million, according to the Santa Clara Division of Agriculture. More than 5,600 tons were produced that year with about three to five tons produced for every acre.
“There are some concerns because we know how destructive the insect can be, but I believe we are taking some precautions to not transport the insects around the area,” said Vic Vanni, the owner of Rancho de Solis Winery and also the president of Wineries of Santa Clara Valley.
The Solis winery operates 16 acres and is about three miles from where the moths were found. Vanni said the quarantine won’t affect his winery as severely as it could others since they don’t export any products outside South County. Though they will have to double press the white wine grapes as part of the precautions asked of them by the county agriculture department.
“It’s good timing we found it now, rather than later during the harvest,” Vanni said.
Thirty-nine grape growers accounting for 620 acres of grapes will be affected by the quarantine. The grape growing season is coming to an end, with the harvest usually timed for October.
“It’s really scary,” said Jan Garrod, the Santa Clara County Farm Bureau’s president and owner of Cooper-Garrod winery in Saratoga. “The unfortunate things this is the end of the season. Now, they’re going to go into the ground, under the debris and we won’t see them again. I know the ag commissioner is going full barrel to see how extensive the problem is. Any time we have an invasive species like this, we got to get it right away.”
Last year, the European grapevine moth was discovered in Napa, Sonoma and Solano counties, causing a 162-square-mile quarantine and major concerns by the state’s most lucrative area for grape growing and winemaking. Statewide trapping ensued and quarantine restrictions are now in place in each of those counties.
The boundaries of the quarantine in Santa Clara County will generally be Llagas Road in Morgan Hill on the north, Foothill Avenue and New Avenue in Morgan Hill, San Martin and Gilroy on the east, Miller Avenue in Gilroy on the south and the Santa Clara – Santa Cruz County line on the west. The quarantine will regulate the movement of bulk grapes, harvest bins, equipment and other articles that may harbor European grapevine moth.
“We’re not sure how they got here, but they likely hitchhiked from an infested area. They could have come up from Napa last year in a bin or on trellis material. It’s unclear,” O’Day said.
The moth hails from Europe, South America, North Africa, Israel and now California. The first appearance of the species in the United States was in September 2009 in the Napa infestation.
The possible damage to South County wine growers could be extensive if not halted, and it’s dependent on whether they can be eliminated before the moths become larvae and spread. The traps are used only to detect how many moths may be in an area – not to eliminate them. If need be, pesticides or mating disruption strategies using pheromones could be the next step in eradicating the pests.
South County has slightly more than 1,500 acres of grapes – the largest cluster of grape growers in the county, Garrod said.
“It’s nothing to sneeze at. But I think (O’Day) is being optimistic. They’re putting the traps out there before these moths go into the dormant state. (In the spring), they’re going to be bigger. We don’t know what’s going to happen,” he said.
Staff writer Miranda Simon contributed to this report.
For more on the moth including a video, go to
