From: Jim Wasserman, The Sacramento Bee
Published June 1, 2005 12:00 AM

Agronomists Import Wasps to Help Wipe Out Grapevine Pest

A Minnesota wasp that lives for a week, loves the cold and is no bigger than an ant is about to be the glassy-winged sharpshooter's worst nightmare.

Welcome to California, Anagrus epos.

The state received permission last week from the U.S. Department of Food and Agriculture to release the tiny, stingerless wasps in Southern California areas that have had past infestations of the sharpshooter, which spreads the fatal Pierce's disease to grapevines.

At least 2,000 of the wasps that are born, raised and lay eggs within a week are holed up in Riverside, reproducing and ready for duty within days.

"If it got in a fight with a grain of rice it would probably lose," said California Department of Food and Agriculture spokesman Jay Van Rein.

But put one of the wasps near a dozen eggs laid by the dime-sized sharpshooter that spreads Pierce's Disease in California vineyards and it will lay 10 eggs on top of them, kill the majority, then hatch new wasps to take the fight elsewhere. Entomologists view the wasps as a new version of history's oldest battle tactic: surround the enemy and overwhelm it.

"In one week those 10 hatch. You now have 10 mature ones laying 10 more. You go from one to 10 to 100 to 1,000 to 10,000," said retired UC Farm Adviser Don Luvisi of Kern County.

The tiny wasps that recently came west from Minnesota with federal agricultural officials, will join four other wasp species that have warred with the sharpshooter and its six-month life span since 2000. The Minnesotans' first assignments include Temecula-area vineyards, Ventura County nurseries and Kern County citrus.

Northern California infestations also have appeared in Vacaville and in Sacramento County.

Van Rein said state agricultural facilities in Riverside and Arvin have released more than 1 million traditional wasps. But those tend to lay only one egg inside a dozen-egg sharpshooter egg mass and are just becoming active in May when sharpshooters begin reproducing.

The new cold-weather wasps will get to work earlier, he said, controlling May's initial sharpshooter outbreaks as well as those later in the growing season.

Vineyard owners fear the glassy-winged sharpshooter for its ability to infect grapevines with a disease that clogs their circulatory systems.

"We're hoping that it will help us with the first generation of egg masses so the population won't have an opportunity to build," said Ben Drake, who heads a vineyard management firm in Temecula and chairs the California Association of Wine Grape Growers.

"We don't know if it's going to work until we try it," added Pete Downs, government affairs specialist for Santa Rosa-based Kendall-Jackson Wine Estates and vice chair of CDFA's Pierce's Disease and Glassy-winged Sharpshooter Board.

Downs said the wasp looks promising and called it "a very positive thing, but added, "The threat is still there."

Bee staff writer Dale Kasler contributed to this story.

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Source: Knight Ridder/Tribune Business News

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