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An urgent warning issued Tuesday by Napa County’s agricultural commissioner has sparked concern across California after an invasive insect linked to devastating vineyard disease was discovered in grapevines sold at Costco Wholesale and distributed across multiple counties.
Officials confirmed that shipments of grapevines originating from Burchell Nursery in Fresno County were delivered to Costco locations serving Napa, Sonoma, Marin, Solan and Yolo counties.
The affected stock, 220 grapevines in total, was shipped between April 21 and May 26 and included plants sold at Costco Wholesale in Napa.
The concern centers on the glassy-winged sharpshooter (GWSS), an insect resembling a cricket that poses a major threat to California’s agricultural industry.
Though harmless to humans and pets, the pest is highly destructive to plants because it spreads Pierce’s disease, a bacterial infection that blocks water-conducting systems and ultimately dries out vines.
The disease has no cure.
Inspectors have already removed and destroyed part of the shipment after detecting GWSS, according to Napa County agriculture commissioner Tracy Cleveland.
“63 of the 220 grapevines delivered to Napa Costco have been destroyed and one GWSS egg mass was found.” The remaining 157 grapevines “may be in the possession of community members who purchased them at Napa Costco,” the statement added.
Costco is now directly contacting affected members and is cooperating with county agriculture officials.
“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,” Cleveland said. “I am confident that the community will pull together to help us limit the risk to our local agriculture. Vigilance and prompt reporting are essential”.
Officials noted that in May, grapevines are typically in bloom with small fruit forming, but infection can stunt growth.
Visible “scorched” leaves, however, often do not appear until late summer, making early detection difficult.
Authorities warned of the potential long-term consequences if the insect becomes established.
“They would be difficult and costly to eradicate, and the increased losses from Pierce’s disease could devastate the local vineyard, winery and tourism industries,” reads a page dedicated to the pest on the county’s website.
Historical data underscores the threat.
A 2008 University of California study found that between 1994 and 2000, Pierce’s disease caused nearly $30 million in losses and destroyed more than 1,000 acres of grapevines in Northern California.
In 2019 an outbreak was prevented in Sacramento County after serious quarantine measures, according to reporting from The Sacramento Bee.
The glassy-winged sharpshooter was first detected in California in 1994.
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