Sharpshooters. The name has a certain ring to it in reference to the Wild West. But in California’s part of the West, glassy-winged sharpshooters — grapevine killers — are persona non grata.

While the California Department of Food and Agriculture marks probable arrival in the state as somewhere in the late 1980s, first reports didn’t come in until 1994. Then in 1999 in Temecula Valley, the first evidence of a real infestation of the half-inch long flying insects was found when some 2,500 of 3,500 acres of vineyards were wiped out.

Outcries were minimal again until an infestation was discovered in set traps in a residential area of Vacaville off I-80 in the fall of 2021. After the initial discovery of a few adults, another 45 GWSS were found along with egg masses on plant material in the area. The Daily Republic local newspaper described the area as having 4,000 acres of winegrape production with a $20 million crop value.

With additional systemic applications applied and additional survey activities planned, CDFA’s Karen Ross said: “It’s a testament to growers’ steadfast commitment to the cooperative Pierces’s Disease Control Program that we’ve been able to eradicate 18 localized infestations since the initial detection.”

GWSS infestations have mostly been contained in the southern San Joaquin Valley and Southern California and the 2021 infestation in Vacaville is the only current hot spot north of the Madera area. Other infestations have been reported in some portions of Los Angeles, San Diego, Ventura, Orange, Riverside and San Bernardino.

In a recent news release, the Pierce’s Disease/Glassy-Winged Sharpshooter board recommended $2.7 million for 16 new research projects over the next three years while noting that they have invested close to $52 million over the last 20 to protect vineyards, prevent the spread of pests and diseases, and deliver sustainable solutions.

“The eradication efforts are in full force against the GWSS infestation in Vacaville’s Browns Valley neighborhood in Solano County,” they report. “Over 900 stingless wasps, natural enemies of GWSS, have been released as sustainable, non-chemical pest management tools to suppress GWSS populations.” Additional biocontrol wasps will be released every few months and sticky traps have been set up in the area to monitor any GWSS population.

Minimize impact

CDFA’s mission in the Pierce’s Disease Control Program is to minimize the statewide impact of the disease and its vectors and toward that end, they report: “Since 1999, we’ve enjoyed many successful harvests — even in places like Temecula — where almost no one was willing to bet on the future of that region. We have every confidence that this on-going effort will continue to build upon its successes until the job is done.”

Mission success is important as USDA ARS publicizes that, “In the San Joaquin Valley, Agricultural Research Service scientists have the sharpshooter in their crosshairs. From an economic standpoint, Pierce’s disease costs California’s grape industry about $104 million per year.”

Priscilla Yeaney is Solano County’s Assistant Agriculture Commissioner and reported: “We’ve surveyed over 1,500 properties in this mostly-isolated residential neighborhood and chemically-treated 625 of them. We released 900 wasps, GWSS enemies, as a bio-control effort in April, and plan a similar release in June and every two months during the summer.”

While there is no way to pinpoint why this geographical area became a point of infestation, no vineyards have been threatened. “We’ll continue to trap and follow-up with treatments where necessary,” said Yeaney. “We’re giving it everything we’ve got and we’ll just keep doing what we’re doing for as long as it takes to beat this thing.”