San Joaquin County agricultural officials are urging residents to isolate recently purchased grapevines after an invasive pest that can threaten vineyards and other crops was found on grape plants sold at Costco stores across Northern California, including in Stockton, Lodi, Manteca and Tracy.
The county’s agricultural commissioner’s office said in a press release that the affected grape plants came from a wholesale nursery in Fresno County and were distributed to Costco stores throughout the wider Northern California region, including the Central Valley.
Residents who bought grapevines from Costco locations in affected counties between April 21 and May 19 should not plant, move, return or throw away the plants, county officials said. Instead, they should isolate the plants and contact the county agricultural office to arrange an inspection.
The pest, known as the glassy-winged sharpshooter, is a type of leafhopper that can spread Pierce’s disease, a bacterial disease that can kill grapevines by blocking the plant’s ability to move water. The insect can also affect almond, citrus and ornamental plants.
The alert comes as agricultural officials across Northern California work to locate grapevines sold through Costco stores after glassy-winged sharpshooters were detected in plant shipments. Napa, Sonoma, Solano, Marin and Yolo counties have also issued warnings or reported related detections connected to Costco plant shipments.
The warning carries particular weight in San Joaquin County, where agriculture remains a multibillion-dollar industry and grapes are one of the county’s signature crops. The county’s gross agricultural production was valued at more than $3.1 billion in 2024, according to the latest San Joaquin County crop report. Grapes were valued at just over $319 million that year.
County officials said Costco has been cooperative and responsive during the process and is not responsible for the discovery, which officials said originated at the nursery supplier level. A public statement from Costco Wholesale was not immediately available Wednesday.
“The GWSS poses a significant threat to a wide range of agricultural commodities, making the prevention of further spread critically important,” the County Agricultural Commissioner’s Office said in its notice.
County officials said the food supply is not affected.
Residents affected are asked to keep the plant in its original pot or container and away from other plants. If the plant has not already been placed in the ground, officials said it should not be planted.
If possible, residents should place the plant inside two sealed trash bags, one inside the other, but should not put it in the trash or compost bin, officials said.
Residents should contact the County Agricultural Commissioner’s Office at 209-953-6000 or StocktonAg2@sjgov.org to arrange an inspection.
An agricultural inspector will examine the plant and nearby host plants. If glassy-winged sharpshooters are found, inspectors will safely remove and dispose of the plant, according to the county. Monitoring traps may also be placed on the property.
For more information, residents can visit the California Department of Food and Agriculture’s Pierce’s Disease Control Program.