Mendocino County Agricultural Commissioner Issues Update on Costco Grape Vine Shipments

No GWSS life stages have been detected in local samples; however, several lab results are pending. Heightened surveillance continues to protect vineyards.

Ukiah, CA – The Mendocino County Agricultural Commissioner’s Office has completed inspections of still in stock grapevine plants shipped from Burchell Nursery in Fresno County to the Ukiah Costco Wholesale store. Laboratory testing conducted by the California Department of Food and Agriculture (CDFA) confirmed that nymph samples collected from these shipments were not glassy-winged sharpshooter (GWSS). We are now working with the public to locate, remove, and safely destroy infested plants before the pest can become established. Additionally, recent insect samples are being analyzed by CDFA laboratory. 

Despite the negative results, the department has taken proactive measures in response to confirmed GWSS detections in multiple neighboring counties, including Marin, Sonoma, Solano, Sacramento, and Napa.

Mendocino County, along with other Agricultural Commissioners in multiple non-infested GWSS counties, have launched emergency efforts to identify nursery plants purchased at Northern California Costco Wholesale locations that may be infested with the glassy-winged sharpshooter, a destructive invasive pest that poses an immediate threat to the state's grape industry. 

“While our initial sample lab results came back negative, we are treating this situation with the highest level of vigilance because of the serious threat GWSS poses to our wine grape industry,” said Angela J. Godwin, Mendocino County Agricultural Commissioner. “Early detection and rapid response are essential to protecting Mendocino County’s vineyards and agricultural economy.”

Actions Taken in Mendocino County

• Costco Wholesale voluntarily removed and disposed of all remaining suspect plants from the Ukiah store.
• Enhanced GWSS detection traps have been deployed at the Ukiah Costco location and surrounding property.
• Trap density has significantly increased in the Anderson Valley, a key wine grape production area.
• The department is working directly with Costco to notify customers who purchased grapevine plants from the Ukiah store between April 24 and May 19, 2026.

Public Guidance Anyone who purchased grapevine plants from the Ukiah Costco during this period is asked to:

• Keep the plant isolated in its original container and do not plant it if you have not already done so.
• Contact the Mendocino County Agricultural Commissioner’s Office immediately at (707) 234-6830 or agcomm@mendocinocounty.gov for inspection and guidance.
• If possible, place the plant in two secured trash bags (one inside the other) until an inspector can respond.
• Do not place potentially affected plants in household trash or compost bins.

About the Glassy-winged Sharpshooter

The glassy-winged sharpshooter (Homalodisca vitripennis) is an invasive insect that feeds on plant xylem and can transmit Xylella fastidiosa, the bacterium that causes Pierce’s disease — a fatal disease in grapevine with no known cure. The pest can also damage almonds, citrus, and many ornamental plants. It is known to feed on more than 250 plant species.

Mendocino County is coordinating closely with CDFA’s Pierce’s Disease Control Program and neighboring counties to prevent the establishment of this pest in the North Coast region.

Additional Resources

• CDFA Pierce’s Disease Control Program: www.cdfa.ca.gov/pdcp

•  CDFA Pierce’s Disease Control Program-GWSS Costco Plant Alert: CDFA - PDCP - GWSS Costco Plant Alert

• University of California Agriculture and Natural Resources – GWSS Information: UC IPM Glassy-winged Sharpshooter Pest Management Guidelines.

Media Contact: Angela J. Godwin Agricultural Commissioner / Sealer of Weights & Measures Mendocino County Phone: (707) 234-6830 Email: agcomm@mendocinocounty.gov

 Download Press Release HERE.