Plagues, Pestilences and Diseases
Grape-destroying moths invade California's wine country
European grapevine moths, unknown to this
country until late 2009, have infested Fresno County.
By Evelyn Nieves, AP
Fri, May 07 2010 at 5:21 AM EST
INSECT WITH EXPENSIVE TASTE: A voracious grape-eating moth has found
its way from Europe to the heart of the Napa Valley. (Photo: California
Department of Food and Agriculture/AP)
A moth with a devastating appetite for grapes is causing worries
San Joaquin Valley, the country's top grape growing region.
The European grapevine moth, unknown to this country until late last
year, has found its way to the region's heart of Fresno County, where
grapes are a $725 million-a-year industry and the valley's top crop.
Three moths were discovered in traps in separate locations in
Fresno County over the last week, and local, state and federal
agriculture officials have started an aggressive campaign to stop the
invader from multiplying.
More than 80 square miles around the area where the moths were
found are under quarantine, meaning growers face heavy regulations on
how to handle their crops and equipment. Chemical treatment is slated
to begin next week.
The good news for the valley's grape growers is that with more
than 5,000 traps set across the county, officials have yet to find more
In Napa County, the nation's storied wine country, 50,000
grapevine moths have been trapped.
"We have a chance of stopping this before it becomes another
Napa," said Les Wright, the deputy commissioner of agriculture for
The moth, about a quarter of an inch in size, is native to Europe,
but is also found in southern Asia, North Africa, South America and the
Middle East. It was first discovered in the United States in Napa
County last fall, when it destroyed the crop of an entire vineyard at
peak harvest time before anyone had recognized it as a new invader.
The moth has since traveled to neighboring Sonoma, Solano and
Mendocino counties, though the greatest number, by far, have been
caught in Napa.
How it made its way to Fresno, 200 miles from Napa, remains a
San Joaquin Valley farmers are already contending with other
pests, including the Mediterranean fruit fly, the light brown apple
moth and the Asian citrus psyllid.
The European grapevine moth, while favoring grapes, will also eat
its way through a long list of tree fruits, including peaches, plums,
nectarines, pomegranates, kiwi and persimmons. It is especially
dangerous to grapes because it feeds on them in both the moth and the
larvae stage — the larva feed on grape flowers and developing fruit.
Second and third generations of the moth cause the most damage
directly by feeding on mature grape berries and indirectly by
predisposing the crop to gray mold, a fungal infection.
The moths lay eggs in April and start their first round of feeding
at the flowering stage.
The pest would have a feast in Fresno. Though the Napa-Sonoma wine
region grows the state's most expensive grapes, the San Joaquin Valley,
and Fresno County in particular, is the nation's largest producer of
grapes, including table grapes, juice grapes and raisins, Wright said.
Fully 80 percent of the raisins consumed around the world come
from Fresno, he added.
In Napa, agricultural officials quarantined about 332 square miles
across wine country on Wednesday after discovering the moth in at least
32 sites, said Elizabeth Emmett, a county spokeswoman.
Barry Bedwell, president of the California Grape and Tree Fruit
League, said that growers are cautiously optimistic that the early
detection of the moth in Fresno will mean it can be stopped before most
grapes are in season.
Grapes are not harvested until late summer.
"Our confidence level is high that we'll be able to catch this on
the onset," Bedwell said.
Still, growers in San Joaquin Valley face potentially major
headaches and expenses. A quarantine means tarping truckloads of the
fruit, washing tractors, mechanical harvesters and fruit bins before
transport and submitting to inspections of fields, packing houses and
Even the seeds and skins left after grapes are crushed have to be
disposed of at a proper facility.
Bedwell, of the California Grape and Tree Fruit League, said that
though farmers face hassles, if the grapevine moth infestation grows,
it could affect the export trade.
"It's a huge problem even at the level that we've found it,"
Wright said. "We're still working out the details of the boundaries of
the quarantine zone and what encompasses the procedure of moving the
farm products out of that region. We don't have all the answers yet.
"And we can't even begin to estimate the costs until we have more