Avenue Vine

Just as California’s grape harvest is coming to a close, so is another season of interest to grape growers: the breeding season for the Glassy-Winged Sharpshooter (GWSS). As the adult GWSS prepare to ride out the winter, growers, researchers and officials gathering for an annual Research Symposium in San Diego next week are breathing a sigh of relief as recent infestations of the GWSS have been held to a minimum and previous ones appear to be controlled.

“With each passing year, our growers and researchers are gaining knowledge and new tools that we hope will eventually allow us to prevail over this very serious pest,” said Bob Wynn, Statewide Coordinator for the California Department of Food and Agriculture’s (CDFA) Pierce’s Disease Control Program. “A lot of credit also has to go to the county agricultural commissioners who are on the front lines of this fight. Their continuing vigilance has been one key to keeping the sharpshooter at bay.”

Since the sharpshooter was first discovered spreading Pierce’s disease in Temecula in 1999, a cooperative statewide response involving local, state and federal governments, growers, scientists and others has succeeded in keeping the infestations in check. Pierce’s disease still poses a grave threat to grapes and several other crops, and no “silver bullet” has been found that can solve the
problem. Researchers continue to make advances and provide new tools for growers who are learning to manage sharpshooter infestations or to monitor crops to make sure vineyards remain free from this pest.

Scientists and other stakeholders in the Pierce’s Disease Control Program will gather at the Marriott Hotel and Marina in San Diego December 6-7 for the annual Research Symposium, where researchers will report on progress made during the past year.

Sharpshooter infestations are currently being managed in several California communities. Here is an update on activities over the past year:

Butte County – Treatments were made at one site along Highway 99. No GWSS have been found since July 2004.

Fresno County – GWSS were found on 325 properties and 1,189 properties were treated.

Imperial County – There were GWSS finds in Salton City. GWSS on the east side of the Salton Sea have been eradicated.

Monterey County –One adult GWSS was found. 145 traps were set out and 182 properties were surveyed. To date no additional GWSS have been found.

Sacramento County - In Rancho Cordova, 460 properties were treated, six GWSS were found in August, but none have been found since. At Foothill Farms, 23 properties were treated and 800 biological control agents (wasps) were released. No GWSS were found in 2005.

Santa Clara County – In Cupertino, nothing has been found since September 2003. 700 biological control agents were released. In Blossom Hill, 15 GWSS positive properties were found and 283 properties were treated while 2,238 biological control agents were released. In Branham, five GWSS positive properties were found and 31 properties were treated while 1,414 biological control agents were released.

Solano County – In May, 13 spent eggs masses and 2 nymphs were found. 6,624 properties were surveyed with all the GWSS finds confined to the landscaping around Wal-Mart. 3,645 biological control agents were released. To date no additional adult GWSS have been found.

Tulare County – 70 positive properties were found in Porterville with 2,695 properties treated this season.

The PD/GWSS Board, made up of wine grape growers and grower/vintners from around the state, advises the CDFA secretary on the expenditure of assessment funds to ensure that the research is responsive to the needs of the grower community. Over 100 research projects are already being funded, providing the science needed to effectively control the pest while also building a research foundation to better understand and address Pierce’s disease.