Glassy-Winged Sharpshooter Infests Grapevines Sold at Ukiah Costco

A grapevine-killing pest has reached the Ukiah Costco, threatening vineyards across Mendocino and Lake counties. The glassy-winged sharpshooter, an insect that can spread the bacterium Xylella fastidiosa—the cause of Pierce’s disease—was found on plants sold at Costco stores throughout California this spring, including the Ukiah warehouse.

On May 19, inspectors seized and destroyed remaining stock, but many plants had already been sold and taken home by shoppers, scattered in backyards across Mendocino County and into Lake County. The state has no sure way to locate them.

The Ukiah store may have sold more infested plants than any other location. “Our store did sell, I think, the largest number of plants before it was caught,” said Lorenzo Pacini, a Mendocino County grape grower who chairs the Mendocino Winegrowers Inc.

grower committee, at a May 27 briefing called by the California Department of Food and Agriculture (CDFA). “They destroyed all the plants at this store, but we don’t know where the rest of them went—and the Ukiah Valley is our largest grape-growing region in the county,” Pacini added.

The glassy-winged sharpshooter has been in California for decades, primarily in the south and Central Valley. The North Coast already hosts a native carrier, the blue-green sharpshooter, but that species mostly stays near creekside brush.

The glassy-winged variety travels farther, feeds on a wider range of plants, and moves with nursery stock—which is how a southern pest ended up on a pallet of grapevines in Ukiah. Once Pierce’s disease takes hold in a vine, there is no cure; the vine dies within five years.

The infested vines came from a Fresno County nursery and were sold through Costco. The problem first surfaced in Santa Rosa, where Sonoma County inspectors spotted suspect sharpshooters on the plants.

Marin County found them next at the Novato store, from the same shipper. The shipment arrived without notice that it needed inspection.

Warnings were then sent to every county that had received the plants.

Costco has told customers who bought a grapevine since April 21 to contact their county agricultural commissioner for inspection. Counties are conducting “trace-forward” operations to track each sold plant, but the state cannot directly reach buyers.

“We have inquired with Costco early on,” said Stacie Oswalt of CDFA’s Pierce’s disease control program. “They disclosed that it’s not their policy to give out customer information.” Costco cited member privacy concerns.

Containment now depends on customers reading a Costco message and voluntarily calling their county ag department.

Growers are skeptical. “Everyone deletes an email from Costco,” Pacini said at the briefing.

He urged the agency to compel the records: “I’m pretty sure we could probably get a court order to subpoena Costco’s records. They destroyed all the plants in their store, so I don’t know why we wouldn’t be destroying those plants as well.” CDFA’s chief counsel, Haig Baghdassarian, said the agency is weighing options.

“There may be avenues, as you suggested,” he told Pacini. Because several counties are involved, he said, the state attorney general’s office “may take an interest” and help move faster—something CDFA would be “exploring in the coming hours.”

Even obtaining the records might not eliminate the danger. Michelle Pham, also with the Pierce’s disease control program, noted that Costco knows which members bought the plants, “but those may not correlate to where those plants actually went.” Joseph Damiano, the CDFA official who ran the briefing, acknowledged the limits.

The plants went “in different places,” he said, and between emailed notices and incoming calls, “we may not find everything.” The agency, he said, is “relying on public information to come back.”

In an interview with The Mendocino Voice, Pacini expressed frustration with the state, not local officials. The county had acted quickly—Mendocino’s agriculture department sent the first notice, and counties including Napa and Mendocino issued press releases.

But CDFA, he said, was slow to respond. “This is the state’s responsibility.

This is CDFA’s responsibility,” he said. “Where have you guys been, and why are you showing up to the party now?” He said he had to ask the agency directly what it was doing to find the plants.

The answer, he said, was that it had talked to Costco, and Costco would not release the buyer list. “And then they ended the sentence.” Pressed on the plan, he said he heard a promise to send another email in a week.

Lake County faces the same risk. It has no Costco of its own; its growers and residents drive to Ukiah.

“This is extremely concerning to our region as well,” said Jenny Keller, president of the Lake County Winegrape Commission, who also asked the state to obtain customer records “if at all possible.” Pacini, who farms in both counties, described the store’s reach: one Costco drawing buyers from Lake County across to northern Sonoma and up toward southern Humboldt.

The vines have been out since late April, more than a month. The sharpshooters found on them appeared in more than one life stage—a sign they could breed, not just travel on the plants.

Inspectors also found a single confirmed nymph on a plant next to the grapevines at one store; that plant was pulled and destroyed, and nearby stock tested clean.

Stuart Spencer, executive director of the Lodi Winegrape Commission, said the window for action is short. If the pest settles into the wild, he said, “getting in there and eradicating them is going to be nearly impossible.” In his experience, people who get an email from a store “are not going to be responding quickly.”

So far, extra traps set at affected stores and at homes inspectors have reached have caught no new sharpshooters, though the trace-forward that began May 19 is only a few weeks old. No stores were fumigated; CDFA said treating a building the size of a Costco that way is not practical.

CDFA is asking anyone who bought a grapevine at a Costco since April 21—in Mendocino, Lake, or elsewhere on the North Coast—to call their county agricultural commissioner before the plant goes near a vineyard, or if it is already in the ground. The agency said it expects to brief the industry again within the week.