MONDAY, JULY 21, 2025. BY STEPHANIE BOLTON, PhD, LODI WINEGRAPE COMMISSION.
Thankfully, California winegrowers recently voted to extend funding for the California Department of Food and Agriculture’s (CDFA) Pierce’s Disease/Glassy-Winged Sharpshooter (PD/GWSS) assessment through 2031. This funding helps us protect our wine industry from several pest and disease threats.
As a reminder, glassy-winged sharpshooter (Homalodisca vitripennis) infestations are still considered active as far north as El Dorado County, Solano County and Stanislaus County while the Pierce’s Disease Control Program (funded by the above-mentioned assessment) attempts eradication.
The population of breeding glassy-winged sharpshooters in the area of Turlock (Stanislaus County) is of particular significance to the Lodi AVA due to it’s proximity to San Joaquin County, and is extra alarming because many people missed the news that this infestation even exists. Thank you to Dr. Keith Striegler (E. & J. Gallo and Lodi Winegrape Commission Research, Education & Communication Committee Member) for making sure we have the information we need.
Although the first finds of glassy-winged sharpshooters in Stanislaus County occurred in early August 2024, the CDFA did not release information on the discovery until October 2024. You can read the full CDFA bulletin HERE.
The PD/GWSS Board also briefly mentioned the infestations in El Dorado, Solano and Stanislaus Counties in their late Fall 2024 Newsletter and more recent issues. However, only one popular news outlet seems to have picked up the story – AgNet West.
With today’s overload of email newsletters and information, we made sure to discuss with the CDFA the dangers of important news (such as a new glassy-winged sharpshooter infestation!) not successfully reaching the mainstream network of viticulture professionals, and how we can improve this relay of information. After all, prevention through rapid response is key.
Luckily Keith and I, plus colleagues Michelle Moyer (WSU) and Hans Walter Peterson (Cornell), created an up-to-date online directory of viticulture and enology extension professionals for the National Grape Research Alliance that should help governmental organizations such as the CDFA with rapid dissemination of crucial pest and disease information.
So, what is the latest news on the Turlock glassy-winged sharpshooter find? According to our San Joaquin County Agricultural Commissioner, Kamal Bagri – who responded to our inquiry in just one hour! – “This year (2025), Stanislaus did find some more insects, but they were within the quarantined area. Delimitation trapping surveys and treatments are continuing and we are keeping a close eye on this.”
Matt Kaiser (CDFA) also quickly responded to our phone call about this too-close-to-home breeding population, letting us know that eradication is not declared official until there is a two-year time period without a find. He also pointed us to a March 2025 PD/GWSS Newsletter stating, “In response to continuing financial challenges, the Pierce’s Disease Control Program is decreasing trapping in its areawide control program by 60% for the 2025 season to prioritize funding for treatments.” This same Newsletter mentioned that glassy-winged sharpshooter detections nearly quadrupled in Fresno County and Tulare County in 2024.
Below is a CDFA-produced map of California showing the current (blue) and eradicated (red) infestations of glassy-winged sharpshooter as of May 13, 2025 (click to Zoom in):
WHAT YOU CAN DO TO HELP PROTECT OUR VINEYARDS & WINE INDUSTRY
With severely decreased funding for glassy-winged sharpshooter control programs further south in the state and the documented movement of the insect northwards, it is imperative that we all take more personal responsibility for early identification of this insect pest.
In addition to supporting the funding of the CDFA PD/GWSS programs, California growers can make sure that they and their employees know how to identify and report the glassy-winged sharpshooter insect and Pierce’s Disease symptoms. If you are a LODI RULES grower, this is in your sustainable winegrowing certification program (LR 3.15 Invasive Species Training and Recognition). The CDFA has resources for identification HERE. The image of the glassy-winged sharpshooter used to make the cartoon above was from this CDFA website, courtesy of the University of California.
The phone number to the CDFA pest hotline, should you find a glassy-winged sharpshooter insect or egg mass in a green area on the map above is 1-800-491-1899.
We will continue to host outreach and education events to teach you how to identify the glassy-winged sharpshooter and Pierce’s Disease symptoms, including at our next IPM meeting about abandoned vineyards on August 5, 2025. We are also doing our part to foster strong, rapid communications through our network of growers, industry, government and university professionals.
Stay informed by signing up for the CDFA PD/GWSS Newsletter by sending an email to pdcpinfo@cdfa.ca.gov or by calling 916-900-5024.
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