California grape growers, vintners, packers, PCAs and others in four counties have successfully turned back the European Grapevine Moth (EGVM).
The California Department of Food and Agriculture has lifted EGVM (Lobesia botrana) quarantines in four counties — Fresno, Mendocino, Merced and San Joaquin — after 2½ years.
The action comes after trapping failed to detect any moths in the quarantine areas over the preceding five generations of the insect’s life cycle.
“It’s a great success story,” says Tye Hafner, deputy Fresno County agricultural commissioner. “Much of the credit goes to the grape growers. It’s not like the government came in and treated their vineyards to control the insect. Growers treated for EGVM on their own, voluntarily eliminating the threat. The entire industry … and representatives of the USDA and California Department Food and Agriculture worked to make the quarantine a success.”
“Millions of dollars were spent by area growers and processors because of increased operational costs to comply with the EGVM quarantine regulations and because of the loss of certain export markets, particularly for table grapes and stone fruit.
Other EGVM quarantines established in 2010 remain in effect in Napa, Nevada, Solano, Sonoma, Santa Clara and Santa Cruz counties.
EGVM was first discovered in the U.S. in September 2009 in a Napa County vineyard, triggering a statewide effort to isolate the pest and prevent its spread.
The EGVM larvae reduce yields by feeding on grape bud clusters or flowers in the spring. Later in the season they feed on ripening grapes, exposing the fruit to fungal development and rot. One Napa County grower lost an entire vineyard to the pest early on.
EGVM was first discovered in Fresno County in April 2010, when two moths were trapped southeast of Fresno in separate locations about a half mile apart. A few days later, another moth was trapped about 11 miles from the original site. A total of six moths were captured during the first flight of the insect and five more were captured during the second flight. The vineyards in that area are mostly Thompson seedless for raisin production, with sometable and winegrape fields.
As elsewhere in the state, Fresno county growers volunteered to treat vineyards within a 1,650 foot radius of known moth finds. The quarantine area covered fields within a five-mile radius of a find. The EGVM quarantine encompassed about 25,000 acres total. In addition to grapes, this area includes stone fruit orchards, olives, pomegranates and kiwis, all hosts for the pest.
Growers affected by the quarantine in Fresno, Mendocino, Merced and San Joaquincounties used either traditional insecticides or organic ovicides and larvicides to eliminate the pest. Due to the low number of insects discovered in the counties in 2010, growers were not allowed to use mating disruption for controlling EGVM because it could have affected the number of adults attracted to pheromone detection traps, causing erroneous trapping counts.
Growers in the three counties seeking deregulation were limited to treating only the first flight in 2011. Any moths trapped after that would have shown that EGVM had not been eradicated. Fresno County grape growers were encouraged to treat fields twice last spring.
Because table grapes are exported, the USDA required table grape growers in the quarantine areas to put out additional traps to further insure that any exported grapes were free of EGVM. Buying and placing the extra traps (five per acre) cost another $8 per acre, an expense paid by the California Table Grape Commission.
Quarantine regulations required growers in these areas to clean equipment with water or pressurized air before it left a vineyard. In addition, growers had to keep records when shipping fresh grapes and other produce, as were handlers of fresh grapes.
“To insure our trading partners that our grapes our EGVM-free, trapping will continue in all the counties that still have an active quarantine, and will also continue in counties that export fresh table grapes,” Hafner says.