California Fights Potential Infestation by Pest that Kills Grapevines

There's a potential disaster unfolding in California. A Fresno County nursery sold table grape vines to Costco for resale in 40 c0unties. Unfortunately, those shipments were found to be infested with Glassy-winged sharpshooters (GWSS). Now, California is racing to recover those vines before the sharpshooters can spread.

This is a concern because the GWSS serves as a primary vector for the bacteria that causes Pierce's Diasease. Once infected, there is no cure. Pierce's Disease clogs the vinee\s water-conducting tissues, and the plant ultimately dries up, shrivels and dies.

Because the sharpshooter is highly mobile and consumes large volumes of plant sap, it can spread the fatal infection rapidly through a vineyard, resulting in massive crop losses. The affected vines must be dug up and destroyed to stop further spreading.

The last major outbreak in California occurred in 1997-1999 and devastated the Temeula Valley, destroying hundreds of acres of vineyards and affecting a quarter of the region's vineyard.

As part of a strict program to prevent the spread of the disease, the California Department of Agriculture & Food requires nursuries in regions known to be invested wth GWSS to flag vines with a "blue-tag" notice. That lets the receiver know to hold them for inspection before selling them.

The Fresno nursery didn't do that.

“There was no notice with these plants and they shipped and went out to the floors immediately,” said Tracy Cleveland, the agricultural commissioner for Napa County. “Then [they] were sold to customers without being looked at by county ag commissioner offices.”

So far, GWSS has been found in 19 of the 40 counties to which the vines were sold. GWSS can travel long distances. Ag commissioners across California are trying to track down and inspect hundreds of grape vines. In Napa County, they've recovered 103 out of 220 sold at Costco. More than 600 potentially infected vines were sold in Sonoma County. Adult GWSS have been confirmed in Contra Costa, Sacramento and San Mateo Counties.

Last week CDFA and thecounty ag commissioners also received customer contact information directly, which allows them to proactively reach out to customers so that the vines can be destroyed and traps can be placed at locations that purchased vines. Costco said it is refunding the purchase price upon request.

Wine Institute said it has been working at state and federal levels to obtain funding to support the work on county ag commissioners to locate infected vines, place traps and inspect traps.