The threat of the European grapevine moth a one-quarter-inch long pest that could endanger California’s table grape crop — and the anxiety level among grower-shippers — appear to be growing.

Another grape pest found in San Joaquin Valley

Calif. Dept. Food & Agriculture


For the second time in as many weeks, moths have been trapped in the San Joaquin Valley. Three of the moths were found May 10 near the Merced County community of Snelling, according to the county’s agricultural commissioner’s office on May 14.

A week earlier, three moths were found in traps in Fresno County, the nation’s top grape-growing county.

The destructive insect had never before been found in California until last fall when the pests were discovered in the Napa-Sonoma wine country, about 200 miles from the heart of the San Joaquin Valley. The wine-country finds triggered a U.S. Department of Agriculture and California Department of Food and Agriculture quarantine, designed to prevent the moth from reaching several hundred thousand acres of table grapes and raisin grape vineyards in the San Joaquin Valley.

The larvae of the European grapevine moth feed on grapes, which render the fruit unmarketable, according the state agency, and make the vines susceptible to fungal diseases.

Pesticide spraying has begun in the valley vineyards in which the moths were discovered and five-square-mile quarantines have been established around each find.

The San Joaquin Valley harvest of table grapes traditionally begins about July 4. However, if the quarantines are expanded, they could cause problems for stone fruit grower-shippers, who have already begun the 2010 harvest.

The moth larvae seem to prefer grapes, but two other San Joaquin Valley crops, pomegranates and olives, are among the more than twenty plant varieties that host the moths.

As of May 14, there have been no further discoveries of the moth reported in the Fresno area, but the county agricultural commissioner’s staff is moving to control and eradicate the insect, according to a news release. A series of meetings is scheduled to begin this week to alert grower-shippers to the threat and to educate them on how to deal with the pest.

The meetings, with the assistance of the University of California Extension Office, are scheduled for May 19 in Parlier, May 22 in Reedley and May 27 in Fresno.

With nearly 200,000 acres of vineyards, grapes are Fresno County’s No. 1 commodity. The value of the 2008 grape crop, the most recent year for which statistics are available, was more than $723 million, according to the county agricultural commissioner’s office.