Medfly infestation in Fallbrook

A Mediterranean fruit fly infestation has been discovered in Fallbrook in San Diego County, Calif.

Two adult male flies were detected in one trap on Oct. 29, and a mated female fly was detected in another trap on Nov. 1.

California Department of Food and Agriculture (CDFA) crews are conducting eradication procedures in the area. Aerial release of sterile Medflies is set to begin Nov. 10 at a rate of 250,000 sterile flies per square mile per week. The release area is approximately 9.33 square miles.

“The release of Sterile Medflies is a proven method of eradicating an infestation,” said CDFA Secretary A.G. Kawamura. “We are ramping up quickly so that we can eradicate this outbreak before it has time to spread throughout this important agricultural region.”

Agricultural officials plan to begin stripping fruit from trees within a minimum of 100 meters of the infested sites so that any larvae possibly inside the fruit cannot survive.

Crews will also apply limited treatments to trees and plants in a 200-meter radius - about one-eighth of a mile - from the sites where the flies were found. The substance being applied is the organic compound Naturalyte (active ingredient: spinosad), a naturally occurring extract from bacteria.

Naturalyte was used in the 2002 Mexican fruit fly eradication program in the nearby community of Valley Center. Residents of these “core” treatment areas will be notified in advance of the treatments.

A brief video about these treatments is available online at:

Sterile male Medflies are brought in from the joint CDFA/U.S. Department of Agriculture rearing facility in Los Alamitos, which prepares hundreds of millions of sterile flies weekly for release over the Los Angeles Basin. The sterile release program has a proven track record 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 eradication of the pest.

An agricultural quarantine in the area is anticipated shortly. Residents are urged not to remove produce from the quarantine zone, and to consume home-grown fruits and vegetables onsite.

The Medfly can infest over 260 types of fruits and vegetables causing severe impacts on California agricultural exports and backyard gardens.

Residents who believe their fruit or vegetables are infested with fruit fly maggots are encouraged to call the state’s toll-free pest hotline at 1-800-491-1899.

The eradication approach in Fallbrook is the standard Medfly program used by CDFA and the safest, most effective program available. CDFA has successfully eradicated each and every detected Medfly infestation in California history, dating back more than 30 years.

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