A Tiny Bug With Billion-Dollar Consequences: How a Fresno Nursery Slipped a Vineyard Killer Into Costco's Wine Country Stores
For the winemakers of Napa Valley, Sonoma, and the surrounding counties that produce some of the most celebrated bottles in the world, the threat usually arrives in the form of drought, fire, or frost. This time, it came in a plastic nursery pot, tucked onto a pallet in a Costco warehouse, priced for the casual weekend gardener who wanted to grow his own grapes. In late May 2026, agriculture officials across California's premier wine-producing regions sounded an alarm that sent shockwaves through the industry: a notoriously destructive invasive insect, capable of wiping out entire vineyards without warning, had been detected on plant shipments sold through multiple Costco locations across the Bay Area.
An invasive insect that threatens vineyards in California was detected on plant shipments delivered to Costco locations across the Bay Area's Wine Country, agriculture officials announced on Tuesday. What began as what appeared to be a routine retail plant sale had turned into a multi-county agricultural emergency — one that underscored just how vulnerable even the most tightly regulated wine regions remain to supply-chain lapses and the movement of infested nursery stock.
The Insect at the Center of the Crisis
The glassy-winged sharpshooter (Homalodisca vitripennis) is a large leafhopper insect native to the southeastern United States. To the untrained eye, it looks unremarkable — a half-inch, brownish-gray bug with glassy, translucent wings and a faint spotted pattern along its body. Nothing about its appearance hints at the agricultural catastrophe it can trigger. But what the insect lacks in menace by appearance, it more than compensates for in what it carries.
First detected in California in the late 1980s, it has since become one of the state's most significant agricultural threats for its role as a vector for a deadly plant bacterium that causes Pierce's disease, which fatally dehydrates grapevines. 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.
The mechanics of how this plays out in a vineyard are grim. In grapevines, it transmits the bacterium Xylella fastidiosa, which causes Pierce's disease — a condition that diminishes vine health and kills the plant, posing a threat to wine businesses and the overall agricultural industry. There is no cure. Once a vine is infected, it cannot be saved — it can only be removed and destroyed, and growers must then wait years before replanting and coaxing a new vine to maturity. The economic calculus is devastating for anyone who has spent decades building a premium wine brand around estate-grown fruit.
The insect's feeding behavior makes it especially dangerous to large-scale agriculture. An adult glassy-winged sharpshooter can drain 200 to 300 times its body weight in water every day, and an infested tree can lose up to 15 gallons per day. The glassy-winged sharpshooter feeds on the xylem fluid of a large number of plants, and is a particular menace to Northern California's grape vineyards. Unlike many agricultural pests that target a narrow range of hosts, this insect is alarmingly catholic in its tastes: it feeds on more than 300 plant species, including grapevines, citrus, almonds, and many ornamental plants commonly used in landscaping.
One characteristic that distinguishes the glassy-winged sharpshooter from its less mobile relatives is its exceptional flight range. The glassy-winged sharpshooter flies higher and farther than native sharpshooters, and can thrive in commercial citrus orchards often planted right next to vineyards. That mobility is precisely what makes its presence inside suburban Costco stores — surrounded by residential neighborhoods, backyard gardens, and ornamental plantings — so alarming to officials. An insect that can cover ground quickly and feed on hundreds of plant species doesn't need much of a head start.
How Infested Plants Ended Up on Costco Shelves
The trail leads back to Burchell Nursery, Inc., a commercial grower based in Fresno County in California's Central Valley. The pest was detected on shipments of grapevines and citrus plants from Burchell Nursery, Inc. in Fresno County to Costco store locations in Napa, Solano, Sonoma and Marin counties, according to officials. The discovery quickly expanded in scope. Napa, Sonoma, Marin, Solano, San Mateo, Santa Cruz and Yolo counties all reported that the glassy-winged sharpshooter had been found in grapevines sold at Costco locations throughout the Bay Area, and on Wednesday, Contra Costa County joined their ranks.
The initial detection came through a standard inspection at a Sonoma County store. On May 19, the Costco Wholesale store in Santa Rosa notified the Department of Agriculture/Weights and Measures that they had received a shipment of grapevines originating from Burchell Nursery in Fresno. During routine inspection, county staff identified multiple suspect life stages of the glassy-winged sharpshooter, a significant agricultural pest capable of transmitting Pierce's disease and posing substantial risk to vineyards and other susceptible crops. Upon discovery, staff contacted the delivering nursery to determine additional delivery points. That single inspection set off a chain reaction that would eventually loop in more than half a dozen California counties.
Critically, the problem wasn't simply one of contaminated plants slipping past inspectors — it was that the nursery apparently never gave officials the chance to check them in the first place. Marin Agricultural Commissioner Joe Deviney said in a press statement that Burchell Nursery was required by state quarantine laws to notify ag offices before shipping, "and that did not occur." The failure to comply with those notification requirements is what allowed infested shipments to travel across county lines and land in the hands of retail customers before any containment could be attempted.
The Napa County Farm Bureau said in a press release that all life stages of the insect were detected on grapevine shipments from Fresno County-based Burchell Nursery to multiple counties, including Marin, Napa, Solano, Sonoma, Yolo and other counties not named. The presence of all life stages — eggs, nymphs, and adults — indicates the colony was well-established in the shipment, not just a stray hitchhiker. These were not insects that accidentally wandered onto a plant in transit; the nursery stock itself appears to have been a breeding ground.
The Scale of the Problem: Hundreds of Plants, Hundreds of Households
The numbers, even as officials scrambled to compile them, were troubling. 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. Officials say they could be in the possession of community members in the Napa area. And that's just one county. It is unknown how many grapevines were delivered to Costco locations in other counties.
The affected plants were received at Costco stores between April 21 and Tuesday, May 26. That's more than a month during which shoppers could have purchased grapevines or citrus plants and transported them home, planted them in backyard gardens, or set them on patios adjacent to neighboring properties. Every one of those scenarios represents a potential vector for spreading the insect further into residential and agricultural areas that were previously free of it.
The response from officials was swift and unusually urgent in its public-facing tone. Agriculture officials in Marin, Napa, Nevada and Solano counties issued a consumer alert "urgently asking residents to take immediate action" — language that reflects genuine concern rather than bureaucratic caution. The instructions were specific and non-negotiable. People who purchased grapevine or citrus plants from North Bay Costco locations in April and May were told to contact their county's agricultural commissioner's office to schedule an inspection. The plant should be left in its original pot or container and sealed in two trash bags, one inside the other. The plants should not be relocated, transported or returned to the store. Do not put the plant in the trash or a compost bin.
The rationale behind those instructions is straightforward: moving an infested plant — even to return it to the store — risks spreading the insect to new locations. Dropping it in a trash bin could allow adult insects to escape containment. Even composting, which might seem environmentally responsible, would release the pest into a garden environment. Officials need trained inspectors to come to the plant, not the other way around.
What Costco and Officials Are Doing About It
Costco, to its credit, has not played defense on this. "Costco is directly contacting members who purchased plants within the timeframe and has been a cooperative partner with all County Ag Commissioners," Napa County officials wrote. The company's membership model — which tracks purchases by card — gives it an unusual advantage in situations like this, allowing it to reach buyers directly rather than relying entirely on public announcements to drive awareness.
County commissioners across the affected region echoed the urgency. "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. "The glassy-winged sharpshooter poses an immediate and serious threat to grapevines and agricultural landscapes throughout Contra Costa County," said Matt Slattengren, Contra Costa County Agricultural Commissioner.
Solano County's top agriculture official put it in plain terms. "Community cooperation is critical right now," said Solano County Agricultural Commissioner Ed King. "If you recently purchased grapevines or citrus plants from Costco, we are asking you to contact the Agriculture Department immediately so we can safely contain and eliminate this threat."
In Marin County, the response extended beyond just the affected Costco plants. Inspectors there surveyed plants from earlier Novato Costco shipments as well as other nearby and commingled plants and increased trapping efforts — an indication that officials are treating the possibility of broader dispersal seriously, not just focusing on the documented sale window.
The Financial Threat to California Wine Country
To understand why agriculture officials are reacting with such urgency, you have to understand the economics of what's at stake. California's wine regions are not just scenic destinations for weekend getaways — they are billion-dollar agricultural economies, and the glassy-winged sharpshooter has the potential to restructure them in the worst possible way.
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.
The timeline for recovery is what makes a GWSS outbreak so potentially catastrophic. Replacing any diseased vines would take years, which could dramatically impact the California wine region economy, as well as impact tourism. A mature grapevine takes three to five years to begin producing commercially viable fruit, and another several years to reach its peak. Premium vineyards in Napa Valley often depend on vines that are decades old. Losing those vines doesn't just mean lost revenue for a season — it means potentially a decade of reduced output, diminished wine quality, and disrupted brand identity for some of California's most prestigious producers.
The University of California reported that the disease destroyed more than 1,000 acres of grapevines in Northern California from 1994 to 2008. That historical record illustrates exactly what's possible when GWSS gains a foothold — and why officials are treating even the possibility of 157 unaccounted-for plants with the kind of urgency typically reserved for wildfire containment.
The Irony of Costco's Relationship With California Wine
There is no small irony in the fact that Costco — of all retailers — sits at the center of this crisis. The warehouse giant has long been one of the wine industry's most important commercial allies. Until just a couple of years ago, Costco was the wine industry's best friend, holding the title of the nation's top wine retailer until 2024. The company's Kirkland Signature wines have won serious critical acclaim, and its buying power has made premium bottles accessible to mainstream American consumers in a way that smaller retailers simply cannot replicate.
Now, however, winemakers are worried the warehouse retailer could, inadvertently, wipe out segments of their vineyards. The tension embedded in that sentence is remarkable: the single most powerful wine retailer in the country, through an entirely unrelated line of garden plants, has become a potential existential threat to the very producers it depends on for its wine business.
This is not a crisis of Costco's deliberate making. The retail chain is not a nursery, and it doesn't inspect every plant that moves through its supply chain with the rigor of an agricultural inspector. It bought from a licensed commercial nursery — Burchell — that was supposed to comply with state quarantine notification laws before shipping. That compliance did not happen, and the consequences are now playing out across nine or more California counties.
The Broader Context: An Industry Already Under Pressure
The timing of this outbreak could hardly be worse for an industry that has been dealing with serious headwinds for several years running. 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.
An industry that was already navigating declining domestic wine consumption, competition from spirits and canned cocktails, and the economic pressures of post-pandemic travel patterns is now facing the possibility of an agricultural pest crisis on top of everything else. The combination is the kind of multi-front challenge that tests the resilience of even the most established wine businesses.
For the smaller family-owned vineyards that dot Napa, Sonoma, and the surrounding counties — many of whom built their operations over generations — a Pierce's disease outbreak wouldn't just hurt the balance sheet. It would threaten the land itself, the vines planted by previous generations, and the sense of place that gives California wine its identity in a global marketplace.
Historical Precedent and What It Tells Us
The glassy-winged sharpshooter was first detected in California in 1994 and is native to the southeastern U.S. and northeastern Mexico, according to the California Department of Food and Agriculture. Its arrival in the state came through the nursery trade — a fact that makes the current situation feel like a failure to learn from history. The pathway that allowed the insect to colonize California in the first place was the movement of infested ornamental plants, and the pathway that is now threatening to seed new infestations across Wine Country is precisely the same.
The state has poured resources into controlling the pest's spread ever since. Quarantine zones, mandatory notification laws before nursery shipments cross county lines, trapping networks, biological control programs using parasitic wasps — all of these tools exist specifically because California learned, the hard way, what happens when the glassy-winged sharpshooter is allowed to move unchecked. The current situation represents a breakdown of those systems at the compliance level, not the scientific or regulatory level. The rules were in place. They simply weren't followed.
What You Should Do Right Now If You Bought These Plants
For any man who picked up grapevines or citrus plants from a Costco in the Bay Area this spring — whether for a backyard garden, a patio, or a home winemaking project — the action items are clear and time-sensitive. Officials urged anyone who recently purchased grapevines or citrus plants from Costco since April 21 to contact their county's Agriculture Department so staffers can contain and eliminate the threat.
The containment protocol is specific for a reason. Residents were directed to place two garbage bags over grapevines to secure them tightly. For citrus plants, people were asked to contact the department to schedule an inspection. The department urged residents not to return, relocate, or give away the plants, and not place them in trash bins or compost containers.
The insect is not dangerous to humans or pets, which is worth noting — this is an agricultural and environmental crisis, not a public health emergency. No one needs to panic about personal safety. But the ask from officials is real, the stakes are significant, and the cooperation of every individual buyer matters. With more than 150 plants unaccounted for in Napa County alone — and an unknown number across the other affected counties — the math is simple: each uncontained plant is a potential point of origin for a new infestation.
The Bigger Picture: Supply Chain Vulnerabilities in American Agriculture
This episode is about far more than a single nursery's compliance failure. It is a window into the fragility of the supply chains that underpin American agriculture, particularly in an era when commercial nursery operations routinely ship plant stock across hundreds of miles, retail giants sell live agricultural products to millions of customers, and the oversight mechanisms designed to catch these problems depend on voluntary compliance at critical choke points.
When that compliance breaks down — as it apparently did when Burchell Nursery shipped without notifying county agricultural offices as required by state quarantine law — the consequences cascade quickly and broadly. A pest that might have been caught and contained at the source instead traveled to a dozen Bay Area retail locations and ended up in the backyards of residential customers who had no reason to suspect their new grapevine carried anything other than the promise of homegrown fruit.
For men who care about American wine — who build cellars, plan trips to Napa, track vintages, and invest in bottles meant to be opened a decade from now — this story is a reminder that the vineyards behind those labels are living, biological systems under constant threat. The men and women who tend them don't just face drought and fire. They face bugs. And sometimes, those bugs arrive at Costco.
