May 28, 2026
Until just a couple of years ago, Costco (NASDAQ: COSTwas the wine industry’s best friend, holding the title of the nation’s top wine retailer until 2024. Now, however, winemakers are worried the warehouse retailer could, inadvertently, wipe out segments of their vineyards.
The Napa County agricultural commissioner issued an alert on Tuesday, warning grapevines sold at Costco had been found to be infested with an invasive insect known as the glassy-winged sharpshooter (GWSS). The insect, which is roughly a half-inch in length, transmits bacteria that’s linked to many plant diseases and can cause Pierce’s disease in grapevines, an incurable infection that blocks water-conducting systems in plants, drying them out.
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A Costco nursery in Napa received 220 grapevines from Burchell Nursery, Inc., which were found to be infected. So far, 63 of those have been destroyed, but the remaining 157 are unaccounted for and officials say they could be in the possession of community members in the Napa area.
“GWSS is a devastating pest for our local vineyards, and it is critical for us to track down any potentially affected plants purchased at Costco or brought into Napa County,” Napa County Agricultural Commissioner Tracy Cleveland said in a statement. “Vigilance and prompt reporting are essential.”
Doubling down on troubles
The threat of Pierce’s Disease is a substantial one. The California Department of Food and Agriculture invests annually in a program to prevent and control the disease and the spread of the glassy-winged sharpshooter. Without those efforts, the department says, growers’ losses would more than double from $48 million to $104 million — and an unchecked spread could cost winegrape growers an additional $56 million a year in lost production and vine replacement.
Replacing any diseased vines would take years, which could dramatically impact the California wine region economy, as well as impact tourism.
That comes as the wine industry saw an unprecedented contraction in 2025, with the largest one-year drop in volume. California alone saw a year over year shipment loss of $142 million, which represented 62% of the industry’s total value decline.
Tasting-room traffic is down as well, and has been for several years. “Relying on people coming to the tasting room no longer works,” one winemaker told Silicon Valley Bank in its 2026 State of the U.S. Wine Industry report.
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Protective steps
To stop the spread of Pierce’s Disease, Napa officials are asking anyone who might have bought an infected vine to not plant it — and to keep it isolated in its original pot or container. If possible, they urge, put the plant(s) in two secured trash bags, sealing them both.
Do not, they stress, attempt to return the plant or move it in any way. And don’t put it in the trash or compost. Instead, they ask that consumers contact the Napa County Agriculture Commissioner’s office, who will send out an inspector that day to examine the grapevine and any nearby agriculture where the glassy-winged sharpshooter might feel at home. They might also put down monitoring traps as a precaution.
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Chris Morris is a veteran journalist with more than 35 years of experience at many of the internet's biggest news outlets. In addition to his activities as a writer, reporter and editor, Chris is also a frequent panel moderator and speaker at major conferences, including CES and South by Southwest.
