Fruit Fly Quarantine Actions in California

Josh McGillPests, Regulation

Fruit Fly
Oriental fruit flies

Portions of Contra Costa and Santa Clara counties in California have been placed under quarantine for the Oriental fruit fly (OFF), and a quarantine in Orange County has been removed. See the updated quarantine map here.

In Contra Costa County, detections near the cities of Brentwood and Oakley have resulted in a quarantine zone covering 99 square miles. The zone is bordered on the north by the San Joaquin River, on the south by Marsh Creek State Park, on the west by Black Diamond Mines Regional Preserve, and on the east by the Old River.

The Contra Costa County action is in response to the confirmed detections of six adult males from various sites in Brentwood by the California Department of Food and Agriculture (CDFA) between Aug. 25 and Aug. 30. Between Aug. 30 and Sept. 5, CDFA confirmed seven additional males from Brentwood. All were from traps in various types of trees in residential areas. 

In Santa Clara County, detections in the cities of Santa Clara and Sunnyvale have resulted in a quarantine zone covering 112 square miles. The zone is bordered on the north by Coyote Creek, on the south by Saratoga, on the west by Mountain View, and on the east by Alum Rock.

The Santa Clara County action is in response to the confirmed detections by CDFA of five adult males and one unmated adult female from various sites in Santa Clara and neighboring Sunnyvale between July 24 and Aug. 24. On Aug. 25, CDFA confirmed one additional male in Sunnyvale and one additional unmated female in Santa Clara. All were from traps in various types of fruit trees in residential areas.

Growers, nurseries or other industry operations that may be located in or near the quarantine zone are encouraged to follow regulatory practices set in place by CDFA.

The 100-square-mile OFF quarantine in Orange County’s Fountain Valley was removed Aug. 19 after three generations elapsed with no additional detections in the area. The quarantine area contained no commercial agriculture. That quarantine was established Sept. 16, 2022, following the confirmed detection by CDFA of six adult males and two unmated adult females from various sites in the Fountain Valley area. There were subsequent detections of larvae and adults between Sept. 21, 2022, and Jan. 4, 2023.

California crops at risk from the OFF include citrus, pome, stone fruits, dates, avocados and many vegetables, particularly tomatoes and peppers.

Additional information about the Oriental fruit fly quarantine areas may be obtained from Fruit Fly National Policy Manager Richard Johnson at 301-851-2109 or Johnson is with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS).

Sources: Citrus Pest & Disease Prevention Program and USDA APHIS

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