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County to hunt for grape-eating insect

San Luis Obispo County agricultural officials are joining the effort to hunt for a tiny bug with a voracious appetite that is threatening California’s multibillion-dollar grape industry.

County Agricultural Commissioner Bob Lilley expects to hire between 10 and 14 seasonal workers to help determine whether the destructive European grapevine moth and another exotic pest that threatens local crops, the Asian citrus psyllid, have spread to the county.

The survey work is expected to start in March and last through the spring and summer. Funding will come from a variety of federal sources.

Surveying consists of placing out traps that use pheromones — mating scents unique to each insect — to attract the bugs. County officials are determining how many traps need to be deployed and expect to have that information next week.

Inspectors are placing 50,000 insect traps throughout the state’s grape-growing regions to determine whether the quarter-inch moth has spread beyond the Napa Valley. If it has, growers will have to brace for costly pesticide treatment campaigns and possible quarantines.

Of particular concern is the grapevine moth, which was recently discovered in Napa County. It is native to southern Italy and has caused widespread damage to wine grapes in Europe. Traps for this pest will be deployed in both urban and cropland areas.

“This moth feeds on the flowers and the small grapes themselves rather than the foliage,” Lilley said. “It will completely strip out a new cluster of grapes so you don’t get a new crop.”

County farm officials are also on the lookout for the Asian citrus psyllid, a pest that has already infested most of Southern California’s citrus growing regions. It spreads a bacterial disease that can be fatal to citrus trees.

Dealing with new threat

The grapevine moth turned up in the Napa Valley in October. It was the first time the pest has been found in the U.S. Nobody’s sure how it got here.

The moth could become the most serious threat since the glassy-winged sharpshooter arrived half a decade ago. That bug has the potential to carry the vine-killing Pierce’s disease, which wiped out about 1,000 acres of vines in the Temecula Valley in Southern California.

A major infestation could cost the grape industry millions of dollars.

The state is working with the U.S. Department of Agriculture on the trapping and treatment program.

Insect traps baited with a pheromone attractant already have been placed in San Diego, Orange, Riverside, Los Angeles, Ventura, Santa Barbara and Sonoma counties, said Steve Lyle, spokesman for the California Department of Food and Agriculture.

In March, hundreds of tent-shaped insect traps will be placed in vineyards throughout Fresno County.

If a moth infestation is found, pesticide treatment plans will be made to keep the bug under control. Several reduced-risk insecticides could be used, as well as mating disruption and parasitic insects.

Regulators also could restrict the movement of plant material and fruit from infected areas.

Such a quarantine could happen soon in the Napa Valley area, where the moth has been found on about 30 properties in the Rutherford and Oakville areas, said Dave Whitmer, Napa County Agricultural Commissioner.

Robert Rodriguez of The Fresno Bee contributed to this story.

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