Medfly Infestation Triggers Quarantine In Riverside County

Taylor Hillman General

Mediterranean fruit fly (Medfly)

Mediterranean fruit fly (Medfly)

cdfa-logoA quarantine has been declared due to a Mediterranean fruit fly (Medfly) infestation detected in Riverside County, in the Perris area. Nine males, three mated females and nine larvae were detected between December 10 and 30th. The United States Department of Agriculture (USDA), the Riverside County Agricultural Commissioner, and the California Department of Food and Agriculture (CDFA) are working collaboratively on this project.

The 83-square mile quarantine is centered over Perris. It is bordered on the north by Oleander Avenue, on the south by Rouse Road, on the west by Post Road, and to the east by Briggs Road. Additional information, including a map of the 83-square mile quarantine zone, is available at:

To eradicate the infestation, the release of sterile male Medflies began December 24, at a rate of over 250,000 flies per square mile per week. The new release area is approximately 13 square miles. In addition, properties within 200 meters of detections are being treated with an organic formulation of Spinosad, which originates from naturally-occurring bacteria, in order to eliminate any mated females and reduce the density of the population. Finally, fruit removal will occur within 100 meters of the larval detection property in order to remove any fruit infested with eggs and larvae.

The quarantine will affect any growers, wholesalers, and retailers of susceptible fruit in the area as well as local residents – home gardeners are urged to consume homegrown produce on site and not move it from their property. These actions protect against the artificial spread of the infestation to nearby regions where it could affect California’s food supply and our backyard gardens.

The sterile male Medflies are brought to California by the joint CDFA/USDA sterile insect rearing facility in Los Alamitos, which prepares sterile flies for release everyday over the Los Angeles Basin. The sterile release program has a proven track record of eradication in southern California. Sterile male flies mate with fertile female flies in the environment but produce no offspring. The Medfly population decreases as the wild flies reach the end of their natural life span with no offspring to replace them, ultimately resulting in the eradication of the pest.

The Medfly can infest more than 250 types of fruits and vegetables, causing severe impacts on California agricultural exports and backyard gardens alike. Residents who believe their fruits and vegetables are infested with fruit fly larvae are encouraged to call the state’s toll-free Pest Hotline at 1-800-491-1899.

The eradication approach in the Perris area of Riverside County is the standard Medfly program used by CDFA and it’s the safest, most effective and efficient response program available. CDFA has successfully eradicated each and every detected Medlfy infestation in California history, dating back more than 30 years.