Oriental Fruit Fly In Contra Costa County Prompts Quarantine

CONTRA COSTA COUNTY, CA— A portion of Contra Costa County is under quarantine for the oriental fruit fly after multiple flies were detected in the county, the California Department of Food and Agriculture said Tuesday.

Detections near the cities of Brentwood and Oakley resulted in a quarantine zone covering 99 square miles, 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 side by the Old River.

The flies were also detected in Santa Clara County near the cities of Santa Clara and Sunnyvale, resulting in a quarantine zone covering 112 square miles, 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.

See the quarantine maps here.

"Invasive fruit flies are serious pests for California’s orchards and backyard gardens," said CDFA Secretary Karen Ross. "These recent detections remind us that we need to remain vigilant in protecting our food supply and natural resources. The stakes are enormous, and not just in California. A new report from the United Nations notes that invasive species management costs hundreds of billions of dollars each year around the world. We’re all in this together as we work to reduce this impact."

The oriental fruit fly is known to target over 230 different fruit, vegetable, and plant commodities. Important California crops at risk include grapes, pome, stone fruits, citrus, dates, avocados, and many vegetables, particularly tomatoes and peppers.

Damage occurs when the female fruit fly lays eggs inside the fruit. The eggs hatch into maggots, which tunnel through the flesh of the fruit or vegetable, making it unfit for consumption.

While fruit flies and other invasive species that threaten California’s crops and natural environment are sometimes detected in agricultural areas, the majority are initially found in urban and suburban communities. The most common pathway for these pests to enter the state, authorities said, is by "hitchhiking" in fruits and vegetables brought back illegally by travelers as they return from infested regions of the world or from packages of homegrown produce from other countries sent to California.

To prevent the spread of this pest through homegrown fruits and vegetables, residents living in quarantine areas are urged not to move those items from their property. However, they may be consumed or processed (i.e., juiced, frozen, or cooked) on the property where they were picked, or disposed of by double-bagging and placing them in the regular trash, not green waste.

Following the principles of Integrated Pest Management, agricultural officials use the “male attractant” technique to eradicate this invasive species. The approach has successfully eliminated dozens of fruit fly infestations in the Golden State, officials said.

Trained workers squirt a small patch of fruit fly attractant mixed with a very small dose of an organic pesticide, Spinosad, approximately 8-10 feet off the ground on street trees and similar surfaces; male fruit flies are attracted to the mixture and perish after consuming it. The male attractant treatment program is being carried out over an area that extends 1.5 miles from each site where the oriental fruit flies were trapped.

Residents with questions may call CDFA’s Pest Hotline at 1-800-491-1899 or visit www.cdfa.ca.gov/plant/off.