When Sonoma County agriculture officials discovered a single light-brown apple moth on Aug. 14 in Carneros, they feared a second moth would turn up, triggering a quarantine that would restrict the movement of flowers and fruit in the area at a time when growers are scrambling to bring in the harvest. They feared things would get worse. Too late.
It turns out the moth they found was the second moth. Napa agriculture officials had discovered a moth in Carneros on the other side of the county line just two days earlier. That means the region, a popular source of Pinot Noir and Chardonnay for both counties, now faces a quarantine.
The light-brown apple moth, native to Eastern Australia, was first sighted in California near Berkeley in 2007. State agriculture officials believe it could have a potentially devastating impact upon California agriculture. It has a potential host range of more than 2,000 plant species, including crop plants such as grapes and citrus fruit, and trees such as redwoods and oaks. In the vineyard, moths lay eggs on grape leaves and the larvae feed on leaves and fruit clusters, leaving them prone to rot.
This is the first moth found in Napa County this year, but the fourth found in the combined Napa and Sonoma areas. The first quarantine was triggered by two moths found in an area northwest of the town of Sonoma this past spring.
As of this week, state and county agriculture officials were still working to define the quarantine area. Officials at the California Department of Food and Agriculture (CDFA) placed traps around the finds in an effort to determine whether there are other moths. "We'll be drawing up compliance agreements with the area growers that lay out the parameters around the movement of fruit," said Dave Whitmer, Napa County agriculture commissioner.
Nick Frey, executive director of the Sonoma County Winegrape Commission, said that under a quarantine, growers will need to have their vineyards examined by agriculture officials within 30 days of harvest. If no insects are found on the property, officials will supply each shipment of grapes leaving the area with a written statement certifying the vineyard to be moth-free.
A plan to set pheromone soaked twist ties that disrupt the mating behavior of the insects in the older quarantine area was scrapped last week by state and county officials, partly because no moths have been discovered in the area since last spring, and partly due to resistance from local residents who feared the twist ties might have adverse health effects. The quarantine is due to end in early October, provided no new moths are found in the area.
Steve Lyle, spokesperson for the CDFA, said that agriculture officials are exploring a new program in which large quantities of sterilized insects will be released so that the wild population cannot reproduce.
According to Lyle, the sterile insect-release program is slated to begin sometime next year, and will become the predominant approach to control and eradication of the insect. Lyle says smaller areas of infestation will still be targeted with pheromone soaked twist ties aimed at disrupting the insect's mating cycles, and that education of the public regarding the safety of the ties will be a key component.