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First Live Glassy-Winged Sharpshooter Found in Napa

Discovery of an adult insect known to spread a vine-killing disease causes some concern in California's most prominent wine region

MaryAnn Worobiec

Posted: Friday, February 23, 2007

For the first time, a live adult glassy-winged sharpshooter, an insect that carries the grapevine-killing Pierce’s disease, has been spotted in Napa; the pest was trapped by a county agricultural inspector yesterday.

The glassy-winged sharpshooter is the farthest-flying and most feared of insects that can spread Pierce’s disease, an incurable bacterial infection that attacks table- and winegrape vineyards. The insect is believed to have entered California in the 1990s via plants shipped in from Florida. Pierce’s disease has already wreaked havoc on Southern California vineyards, and the sharpshooter has moved up through the Central Valley. Grapegrowers and state agricultural officials have been keeping a close eye on the pest to ensure it doesn't gain a foothold in Northern California's prime wine regions.

Previously, only egg masses have been spotted in Napa, usually on ornamental plants brought in from infested counties in the southern part of the state. But hatched eggs have been found as nearby as Vacaville, Calif. "The egg masses are troubling to us, but they’re not mobile. They are not the kind of thing that when they warm up, they fly off,” said Napa County agricultural commissioner David Whitmer. “In the previous seven years of [our] inspection program, we haven’t found any adults or nymphs."

In this case, an adult female was found on a Pandorea jasminoides, also known as a Bower Vine, that had been shipped from an Orange County wholesale nursery to the Napa outlet of a large plant retailer. An inspector was able to grab the insect and put it in a vial, and a state entomologist confirmed the identification.

After the find, the Southern California nursery agreed to take back the plants it had sent to the retail store, according to a press release from Whitmer's office. By 1 p.m. the entire load of plants had been picked up and removed from Napa County. The release also noted that the temperature in Napa yesterday was likely too low for the sharpshooter to have flown elsewhere before it was captured.

The Napa County Agricultural Commission’s strict inspection program, which has been in place since 2000, is the region's key defense against the glassy-winged sharpshooter. Napa County checks for eggs and insects at nurseries on all incoming plant shipments that have the potential to host the glassy-winged sharpshooter. When a new shipment of nursery stock arrives, the county agriculture office is called to inspect the shipment.

Because a pest was found on a shipped plant, California agriculture officials will now review the originating nursery’s inspection program.

“It’s both a positive and negative for us," said Whitmer. "It’s negative from a sense that we found it. Our system shouldn’t be allowing live stages of glassy-winged sharpshooter to move, but I’m gratified that our system in place caught it.”

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