Pest Known for Carrying Grapevine Killing Disease Spreads in California

At a time when California’s wine industry is already facing slumping demand, it’s now facing an added threat—the glassy-winged sharpshooter (GWSS). The non-native insect, which carries the vine-killing Pierce’s disease, is being found in an increasing number of California counties. While state officials have yet to find the pests in commercial vineyards, they’re growing increasingly worried.

The most devastating wave of Pierce’s, an incurable disease caused by bacteria that attacks vines’ ability to draw in water, hit Northern California in the mid-1990s. That wave, caused by the GWSS, destroyed more than 1,000 acres of grapevines and caused $30 million in damages, according to the University of California. A less severe wave, in 2015, was caused by the blue-green sharpshooter, a smaller, related insect that is native to the region.

Earlier this summer, the California Department of Food and Agriculture (CDFA) announced that glassy-winged sharpshooters had been found on grapevines sold at Costco locations in Northern California. The vines came from a Fresno nursery. Officials asked buyers to isolate the plants and contact the state to destroy them.

A CDFA worker holds a sharpshooter in his thumb. Teams have set traps around the state to catch and track the pests. (Courtesy CDFA)

In July, glassy-winged and broad-headed sharpshooters were found on desert willow trees sold at Costco locations in 18 California counties, including Santa Clara, San Diego and Los Angeles. Both species are invasive. Glassy-winged sharpshooters are native to the southeastern United States, while the broad-headed sharpshooter is native to Central America.

“The desert willows originated from a nursery in Texas,” Joshua W. Bingham from the Office of Public Affairs at the CDFA told Wine Spectator. He added that there is an ongoing investigation.

“County agricultural commissioners are locating and inspecting thousands of grapevines. Glassy-winged sharpshooter trapping will continue through the end of September,” said Bingham.

On Aug. 4, state officials identified a GWSS trapped in a nursery in San Luis Obispo county. So far, officials have found GWSS on plants in 22 counties, but the pests may have been carried into as many as 40 counties on plants from the Fresno nursery. More than 3,100 customers who purchased the grapevines have been contacted by officials and more than 2,700 additional insect traps have been set, according to the CDFA.

The state has committed $820,000 in emergency funding to support inspections and trapping for at least three years. That money comes from assessments paid by grapegrowers. California’s two U.S. senators, Alex Padilla and Adam Schiff, requested $32 million in emergency funds from the U.S. Department of Agriculture for tracing and trapping the pests, but were turned down.

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