photo credit: County of Napa
A glassy winged sharpshooter, the invasive pest insect discovered on shipments of 
grapes delivered to North Bay Area Costco locations from a nursery in Fresno County.

Sonoma County's agricultural commissioner has put out an urgent alert to North Bay residents after an infestation of the glassy winged sharpshooter insect was discovered on grapevines sold at multiple Sonoma County Costco locations.

Glassy-winged sharpshooters, with an appearance similar to crickets, can cause Pierce's disease, a bacterial infection that blocks water-conducting systems in plants, drying them out. The disease is incurable.

Grapevines infected with all life stages of the pest have been found in shipments across Sonoma, Napa, Marin, Solano and Yolo counties.

Sonoma County agricultural authorities discovered the pest during a routine produce inspection at the Costco Wholesale in Santa Rosa on May 19th.

The infected grapes were shipped from Burchell Nursery in Fresno County.

A total of 220 infected grapevines were delivered to the Costco Wholesale in Napa between April 21 and Tuesday, May 26th.

In a statement Napa County's agriculture commissioner Tracy Cleveland said, "63 of the 220 grapevines delivered to Napa Costco have been destroyed and one Glassy Winged Sharpshooter egg mass was found." 

Sonoma County staff said glassy winged sharpshooters were also discovered at the Rohnert Park Costco, and they instructed anyone who's purchased grapes at local Costco's since April 21st to tightly secure them in two garbage bags and contact Sonoma County's Department of Agriculture/Weights & Measures.

Cleveland said it is critical for community members who purchased the infected grapevines to notify agricultural authorities and limit the risk of spreading the pest to the region's wine industry.

Costco is directly contacting members who purchased plants between April 21 and May 26th; and has been a cooperative partner with all county ag commissioners.

A 2008 study from the University of California found that between 1994 and 2000, Pierce's disease caused nearly $30 million in losses and destroyed over 1,000 acres of grapevines in Northern California.   

While pest control officials can use pheromone traps to capture adult glassy winged sharpshooters, an infestation would likely be difficult to eradicate, and potentially devastate the Sonoma and Napa Wine Country economy by infecting and damaging wine grapevines with Pierce's disease.