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Wasp Released in California

Wasp Released in California to Combat Vineyard Pest

(August 15, 2000)

A tiny, stingerless parasitic wasp that was imported from Mexico and bred at the University of California, Riverside, is now being released in limited numbers in Riverside County to combat the glassy-winged sharpshooter.

Additional releases are planned soon in Ventura, Kern, Tulare and Fresno Counties, a result of research funded by the California Department of Food and Agriculture (CDFA.)

The non-native wasp is another tool in the fight against the glassy-winged sharpshooter and Pierce's disease, which has already wiped out between $12 and $14 million in Temecula grapevines and is threatening a region in central California that produces $2.8 billion each year in wine, raisin and table grapes.'

'This is a critical piece of the Davis Administration's action plan against the glassy-winged sharpshooter, said CDFA Secretary William (Bill) J. Lyons, Jr. ' We intend to use the wasps along with other control programs to try to control the sharpshooter's movement.'

Entomologists from UCR and the UC Cooperative Extension found and identified a natural enemy of the glassy-winged sharpshooter. The wasp, Gonatocerus triguttatus, is successfully reducing populations of the sharpshooter in Mexico and Texas. The wasp parasitizes the sharpshooter by laying its eggs inside those of the larger insect. Once hatched, the wasps eat their way out.

Prof. Mark Hoddle of UCR, a biological control specialist, led a seven-month breeding and quarantine program, funded by the CDFA and the Californian grape commodity boards. David Morgan, a postdoctoral researcher, has raised the wasps and is releasing them in organic citrus groves and other locations, where they can begin to form field populations.

The glassy-winged sharpshooter, which carries Pierce's disease from plant to plant as it eats, has been found in Riverside, San Diego, San Bernardino, Ventura, Orange, Santa Barbara, Los Angeles, Kern and Tulare counties. The CDFA is fighting the half-inch leafhopper with $6.9 million acquired under the leadership of California Governor Gray Davis. Some of that money helps to fund research at UCR for an ongoing wasp breeding and release program in grape-growing areas infested or threatened by the glassy-winged sharpshooters, including Bakersfield, Fresno and the Napa Valley.

Also, the Governor pursued federal assistance, leading to the passage of a bill in Congress that provides another $22 million to fight the pest.

While pesticides will continue to be the more common weapon against the glassy-winged sharpshooter in large commercial vineyards, biological control agents, like this parasitic wasp, are an important tool in populated urban areas, organic vineyards and wildlands, where pesticide applications are not feasible, said Morgan.

UCR will continue to monitor how well the wasp does in the dry heat of California, how successfully it reproduces, and how well it is able to find and parasitize the eggs of the glassy-winged sharpshooter.

'Our primary goal from these initial releases is to set up stable populations of the wasp in California,' Morgan said. 'We are also investigating the potential of other non-native parasites of the glassy-winged sharpshooter that we will use to bolster the natural enemy arsenal in California.'

The University of California, Riverside ( is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 21,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion.

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