Since the discovery of the first European grapevine moth in North America was made in Napa Valley this past September, industry sources have watched carefully as the moth made its way through Napa County. At one point, authorities believed the moth was confined to some 30 vineyard sites in Napa. But now, according to United States Department of Agriculture spokesperson Larry Hawkins, the moth is confirmed throughout Napa County, and its presence has triggered a quarantine that extends from St. Helena in the north to the southern reaches of the city of Napa. A new quarantine that encompasses Calistoga, in the northern reaches of Napa Valley, and parts of neighboring Sonoma County is expected soon as the result of three adult moths trapped recently in Calistoga.
And the pest is no longer confined to Napa County.
Earlier this month, Sonoma County agricultural officials raised the alarm when they found a single European grapevine moth (EGVM) in a Kenwood vineyard. At the time, Sonoma County Agriculture commissioner Cathy Neville said that if a second moth were to be found in the area, a quarantine would have to be established.
Just last week, a second moth was trapped in the Kenwood area, along with two more found in the southeast portion of the city of Sonoma, triggering two more areas of quarantine in Sonoma County.
Unlike the light-brown apple moth, the EGVM has already demonstrated its ability to do serious damage to vineyards. Last fall they destroyed 100 percent of a 10-acre Chardonnay crop at a Napa Valley site. The moth lays its eggs inside the grape berries and on flower clusters, eating fruit and opening the door for fungal infections such as botrytis.
native to Europe, the moth has been spreading globally. Found in Chile in March 2008, the insect spread north and south from Santiago within months according to Richard Hoenisch, western regional training director for the USDA’s National Plant Diagnostic Network. Hoenisch says it has since invaded Argentina.
How the EGVM arrived in Napa Valley is still a mystery. Hoenisch said, “It’s strange that it appeared right smack in the middle of Oakville.”
Nurserymen and plant importation experts at first thought the insect may have come in on a so-called “suitcase clone,” an illegal importation smuggled in from some foreign vineyard, but Hoenisch says this is unlikely. “The moth doesn’t lay its eggs on the wood, but on flowers and fruits.”
He speculated that the insect could have come from either Chile or Europe, possibly in fruit or on vineyard equipment. “We import enormous quantities of fruit from Chile each year and the insect could have slipped through regular USDA inspection,” said Hoenisch. He pointed out that since 2002, USDA inspectors have intercepted EGVM larvae in figs (many types of fruit can play host to the moth) from Europe as many as 20 to 30 times.
Agriculture commissioner Neville called the threat posed by the EGVM “serious,” saying that the female lays eggs on the fruit, then secretes pheromones that mark the fruit so that no other female will lay her eggs on the same bunch of grapes. “This is the real deal,” said Neville.