The county’s first infestation of the wine grape pest the glassy-winged sharpshooter has been detected in The Arbors residential neighborhood near Islay Hill in southeastern San Luis Obispo.
An adult insect was found in a trap in a home’s yard about 10 days ago as part of the county’s routine pest management monitoring.
This prompted an intensive trapping and surveying effort, which found three more adult insects and multiple egg masses, said Bob Lilley, county agricultural commissioner.
The pest is considered a threat to vineyards because it spreads a bacterium that causes Pierce’s disease, which is fatal to grape plants, the county’s highest-value crop.
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The Islay Hill area is adjacent to many vineyards in the Edna Valley, but the insect has not yet been found in any vineyards.
A one-mile-radius quarantine around the infestation has been established. This means that nursery products must be inspected before they can be shipped out of that area.
“We feel like we’ve found it in a very isolated area and that it has not spread,” Lilley said. “Hopefully, we’ve found it early.”
As part of their intensified surveying, agriculture officials have visually surveyed 522 properties in the area and placed 100 sticky, bright yellow insect traps in yards and in the neighborhood’s many greenbelt areas.
The number of traps is expected to grow to 300 in the next couple of weeks. Concerned vintners have also put traps out in their vineyards, Lilley said.
The discovery of the glassy-winged sharpshooter comes just as the harvest season is under way. Vineyard manager Scott Williams, at Pacific Vineyard Co. in San Luis Obispo, was notified by the county about three weeks ago.
“It’s always concerning when we hear about any type of invasive pest,” he said. “But, we haven’t seen anything out of the ordinary here.”
Sales of grapes from county vineyards totaled $166 million in 2009, or 27 percent of the combined value of the county’s entire agricultural industry, according to the county Agriculture Department.
Agricultural officials will begin an eradication effort in February.
This will consist of injecting Imidacloprid, an insecticide commonly found in pet flea and tick control products, into the soil beneath host plants. The pesticide was chosen because it has low toxicity to mammals, Lilley said.
The host plants will absorb the insecticide, which is supposed to kill the sharpshooter when it feeds on the plant. Citrus trees are the most common host, but a variety of ornamental trees and plants can also harbor the pest.
“Sharpshooters are strong fliers and heavy feeders, so the potential for the infestation to spread is a concern,” Lilley said.
The eradication effort is timed for February to coincide with the active feeding stage of the insect’s lifecycle. Fifty-five properties are targeted for eradication, encompassing each of the properties where the pest was found as well as a three-property radius around the infestation sites.
The state Department of Food and Agriculture is paying for the eradication effort with funds set aside for farm pest management. The survey work has cost nearly $28,000 to date, and the eradication campaign is expected to cost $11,000.
The glassy-winged sharpshooter was first detected in California in 1994. The insects are native to the southeastern United States. The first major infestation occurred in Temecula in Riverside County in 1999, where more than 300 acres of vineyards were destroyed.
Staff writer Stacy Daniel contributed to this report.