Humboldt warns residents after invasive sharpshooter found on grape plants

A grape plant bought at Eureka’s Costco could become a countywide agriculture threat if it carried the invasive glassy-winged sharpshooter, and Humboldt County officials are telling residents to act immediately before the pest has a chance to spread.

The County of Humboldt said the Eureka store at 1006 W. Wabash Ave. was among Costco locations that received grape plants from Burchell Nursery in Fresno County. The county said the problem began at the nursery supplier level, not in the local food supply, but warned that moving, planting, sharing, or discarding the vines without care could create a pathway for an insect that spreads quickly once established.

The glassy-winged sharpshooter is a leafhopper native to the southeastern United States that became established in California in the 1990s, according to the California Department of Food and Agriculture and USDA Animal and Plant Health Inspection Service. CDFA says the insect is a particularly effective carrier of Xylella fastidiosa, the bacterium that causes Pierce’s disease, and USDA says the disease eventually kills grapevines. That matters in California, where grapes account for about 94 percent of U.S. grape production.

UC IPM says the insect has two generations per year in California and can overwinter in citrus, weeds, ornamentals, and various trees. That wide host range makes it a problem far beyond vineyards, since Humboldt gardens, nursery stock, and ornamental plantings can all help sustain the pest if infected plants are moved around. County officials and state agriculture staff say early detection is critical, because infestations in other counties have often been eradicated or suppressed when caught early.

The stakes are not theoretical. CDFA says a major outbreak in Temecula, Riverside County, in August 1999 led to more than 300 acres of grapevines infected with the sharpshooter and Pierce’s disease being destroyed. CDFA also said Fresno County staff and department personnel had been on-site since May 19, 2026, stopping shipments from Burchell Nursery and investigating corrective actions as county agricultural commissioners and Costco responded. Several Northern California counties issued warnings on May 26 and 27, including Santa Cruz and Sacramento counties, underscoring that the alert extended well beyond Humboldt.

Residents who bought grape plants recently should check their purchase, isolate anything suspicious, and contact the county agricultural office before planting, moving, returning, or throwing out the vines. In a county where vineyards, backyard gardens, and nursery businesses all share the same landscape, one retail shipment can turn into a long-term agricultural problem if residents do not stop it early.