Full Breakdown
Invasive Glassy-Winged Sharpshooter Detected on Costco Grape and Citrus Plants Triggers Multi-County Alert in Northern California
5/28/2026, 12:01:23 AM
Immediate Threat Identified
Agricultural officials across Northern California have confirmed that the invasive glassy-winged sharpshooter (GWSS) was found on grapevines and citrus plants sold at Costco locations in Yuba, Sacramento, Napa, Sonoma, Marin, Solano, Yolo, Placer, San Mateo and other counties. The leafhopper transmits *Xylella fastidiosa*, the bacterium that causes Pierce’s disease, a fatal condition for grapevines and a serious risk to almonds, citrus and ornamental plants.
Background on the Pest
Native to the southeastern United States and northeastern Mexico, GWSS first entered California in the 1990s and has since become established in central and southern regions. The insect feeds on more than 250 plant species and can travel greater distances than native sharpshooters, facilitating rapid disease spread.
Key Agencies and Stakeholders
- Burchell Nursery, Inc. (Fresno County) – source of the contaminated shipments.
- Costco Wholesale – retailer distributing the plants; cooperating with officials and directly contacting customers.
- County agricultural commissioners leading the response: Stephen Scheer (Yuba), Chrisandra Flores (Sacramento), Humberto Izquierdo (Yolo), Tracy Cleveland (Napa), Joe Deviney (Marin), Ed King (Solano), Koren Widdel (San Mateo).
- State agencies: California Department of Food and Agriculture (CDFA) and UC Cooperative Extension.
Timeline of Detection and Response
- April 21 2026 – First shipments of Burchell Nursery grapevines arrive at Costco stores.
- May 19 – Sonoma County inspectors discover GWSS during a routine produce check.
- May 26 – Press Democrat reports 634 plants delivered to Sonoma Costco; 241 destroyed, 393 unaccounted.
- May 26 – Napa County confirms 220 grapevines delivered; 63 destroyed, 157 unaccounted.
- May 27 – San Mateo, San Joaquin and other counties issue consumer alerts, advising double-bagging of plants and contacting local agriculture offices.
Scope of the Infestation
- Sacramento County: 160 grapevines destroyed; “hundreds” of vines remain in private hands.
- Marin County: 68 plants destroyed; traps placed at the Novato Costco nursery.
- Napa County: 63 of 220 vines destroyed; one egg mass found.
- Sonoma County: 241 of 634 plants destroyed; 393 still unaccounted.
- Yolo County: Officials stress that preventing further spread is “critical.”
Implications for Vineyards and Other Crops
Pierce’s disease blocks water transport in vines, leading to wilting, reduced yields and eventual death. Historical data show the disease caused nearly $30 million in losses and destroyed over 1,000 acres of vineyards between 1994 and 2000. If GWSS becomes established in the North Bay, almond, citrus and ornamental sectors could also suffer significant damage.
Official Statements & Responses
County commissioners emphasized community cooperation, rapid plant isolation, and the need for double-bagging grapevines and citrus plants. CDFA officials highlighted that early detection is essential to eradicate infestations before they spread. All agencies reiterated that Costco is a cooperative partner, not the source of the breach.
Criticism of Nursery Notification
Marin County officials noted that Burchell Nursery failed to comply with state quarantine laws requiring prior notification of shipments, a lapse that allowed the pest to enter the supply chain unnoticed.
Conflicting Reports & Gaps
Numbers of unaccounted plants differ: Sacramento cites “hundreds,” Sonoma reports 393, and Napa lists 157. No unified inventory exists, creating uncertainty about the true scale of exposure.
Verbatim Quotes
- “Glassy-winged sharpshooters pose an immediate and serious threat to vineyards because they transmit the bacterium Xylella fastidiosa which causes the deadly Pierce’s disease in grapevines” — Stephen Scheer, Yuba County Agricultural Commissioner
- “Now that the glassy-winged sharpshooter has been confirmed on these plants, preventing further spread is critical,” — Humberto Izquierdo, Yolo County Agricultural Commissioner
- “Sonoma County Agricultural Commissioner Andrew Smith was quick to tell the Chronicle, "Costco is not at fault here, and they’ve been an exceptional partner throughout this process.” — Joe Deviney, Marin County Agricultural Commissioner
- “The difference with the glassy-winged sharpshooter is that it’s considerably larger, and able to travel further distances,” — Cindy Kron, UC Cooperative Extension advisor
- “I am confident that the community will pull together to help us limit the risk to our local agriculture.” — Tracy Cleveland, Napa County Agricultural Commissioner
What’s Next
Counties are deploying additional GWSS monitoring traps, conducting on-site inspections, and continuing to contact customers. Residents are urged to keep suspect plants isolated, double-bag them, and refrain from planting, moving, or discarding them until inspected. Ongoing coordination between Costco, county agriculture offices, CDFA and university researchers aims to locate all unaccounted vines and prevent establishment of the pest in California’s wine country.
