Planting Seeds - Food & Farming News from CDFA

News Release – Oriental fruit fly quarantine set in Stockton, San Joaquin County

A quarantine is in place in Stockton and surrounding San Joaquin County, where invasive Oriental fruit flies have been detected.

Multiple flies have been trapped to date on properties near the center of the quarantine zone.  Additional information, including a map of the 118-square-mile quarantine zone, is available at: The zone is centered in Stockton and includes the downtown area, reaching south to Highway 4.

“This quarantine includes both farms and residential properties, so all of us must work together to carry out an effective program,” said CDFA Secretary Karen Ross. “We urge home gardeners to comply with these measures by consuming homegrown produce at home and not moving it from the property.  Your cooperation will protect your fellow gardeners and help ensure that the infestation will not spread to nearby areas where it could affect California’s food supply.”

CDFA has begun working with the local agricultural commissioner’s office to advise farmers of their responsibility to comply with quarantine restrictions that strictly govern the conditions under which they may harvest and transport fruits and vegetables that are known to host the pest.  The primary host crops grown in this quarantine area include grapes, cherries, walnuts, tomatoes and bell peppers.

Following the principles of integrated pest management, CDFA uses “male attractant” treatment as the mainstay of its eradication measures for this pest.  This approach has successfully eliminated dozens of fruit fly infestations from California since the 1970s.  Workers squirt a small patch of fly attractant mixed with a very small dose of pesticide approximately 8-10 feet off the ground on street trees and similar surfaces; male flies are attracted to the mixture and die after consuming it.  The male attractant treatment program is being carried out over several square miles surrounding the sites where the insects were trapped. A detailed map of the treatment area is available online at:

On and near properties where flies have been detected, additional measures include removal of host fruits and vegetables, fruit cutting to detect any fly larvae that may be present, and treatment of host trees and plants with the organic-approved material spinosad.

While fruit flies and other pests threaten California’s crops, the vast majority of them are detected in urban and suburban areas. The most common pathway for these pests to enter the state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions around the world. The Oriental fruit fly is widespread throughout much of the mainland of Southern Asia and neighboring islands including Sri Lanka and Taiwan.  It is also found in Hawaii.

Residents with questions about the project may call the department’s Pest Hotline at 1-800-491-1899.

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