Vintners worry destructive moth threatens low-impact growing methods in Napa Valley

Grape moth threatens Napa Valley growing method

FRESNO, Calif. — When a voracious pest triggered a quarantine this week across much of Napa Valley — the nation’s premier grape-growing region — it threatened more than the grapes themselves.

The spraying of pesticides needed to control the European grapevine moth threatens to undo decades of low-impact farming practices that have elevated the quality of wines from the region.

“That’s a big concern for the growers,” said Bruce Phillips, who grows 70 acres of cabernet sauvignon on the western slope of the valley.

Growers of premium wine grapes have long believed that elegant flavors are tied to the soil.

Phillips, the general manager of the Napa Valley Grape Growers Association, said the third invasive pest discovery in three years “raises the question of the long-term sustainability of organic and biodynamic practices.”

Agriculture officials imposed a quarantine Tuesday restricting the transport of equipment, grapes and even the skins that are left when they are pressed after discovering the pest in at least 32 sites across Napa Valley.

The moth was first detected in the U.S. last September in a vineyard in the center of Napa Valley. The bug managed to destroy the crop of an entire vineyard at peak harvest time before anyone recognized the new invader.

“This is the worst of the invasive species, there’s no question about that,” said Jim Lincoln, who manages 400 acres of vineyards inside the 162-square-mile quarantine area. “It does real damage to the fruit, and it will be expensive to eradicate — if we can eradicate it.”

The Beckstoffer Vineyards, which Lincoln manages, are not organic. But like most growers in the region, he tries to use minimal chemicals on the vines to protect the flavor of his grapes and the environment in which he and others work.

At an average $3,414 a ton for premium cabernet, damage can add up quickly in a county where the crop is worth $400 million annually. One acre can produce between three and four tons of quality grapes.

The moth is the latest stroke of bad luck for the 400 or so Napa Valley vintners who already are suffering from a 15 percent decline in sales of ultra-premium wines and a resulting jump in winery and vineyard foreclosures this year and last.

At the least, the presence of the moth will increase costs at a time when many are trying to cut expenses.

Premium grape growers are now facing the prospect of spraying at least three times in the months ahead to deal with the three generations of grape-eating larvae that are produced each growing season. The spraying could cost at least $200 an acre.

“It’s going to raise the cost of farming, which is very tough in this market,” said grower Steve Sangiacomo, whose vineyard is not in the quarantine area.

The growers association met Wednesday with A.G. Kawamura, secretary of the California Department of Food and Agriculture, to hear an update on the situation.

The European grapevine moth arrived a decade behind the glassy-winged sharpshooter, a potential carrier of Pierce’s Disease. The sharpshooter wiped out 1,000 acres of vines in Temecula in Southern California.

After years of study, authorities now believe the sharpshooter fares poorly in Northern California’s cooler climates.

The small, brown grapevine moth is native to Europe, but is also found in southern Asia, North Africa, South America and other areas.

Grapes are its main target, but it feeds on other California crops and plants such as kiwi, blackberries and persimmons.

The moths lay eggs in April and start their first round of feeding at the flowering stage. Traps have detected it at sites across the Napa Valley, prompting the quarantine that also stretches into parts of neighboring Sonoma and Solano counties.

To determine its range, the California Department of Agriculture recently placed 2,500 traps throughout the Napa Valley to go with the county agriculture commissioner’s 715 in the core infestation area.

More traps are going up in the San Joaquin Valley and in Southern California to determine if other infestations exist.

Meanwhile, farmers will be required to wash tractors, mechanical harvesters and fruit bins when moving outside of the quarantine area.

Even the skins and seeds left after grapes are crushed will have to be disposed of at a proper facility, said Greg Clark, Napa County’s assistant agricultural commissioner.

“The reality is this is a very big deal,” Clark said. “This is a situation that requires immediate action. We can’t wait to know everything about this pest before the quarantine is implemented because of the seriousness of the threat.”