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Medfly quarantine for Escondido

Detection of a mated female Mediterranean fruit fly in a trap in Escondido, San Diego County, on Sept. 9, has triggered a 77-square-mile agricultural quarantine.

Agricultural shipments from the quarantine zone are restricted by regulations designed to minimize movement of potentially infested commodities. In addition, people moving through the quarantine zone are urged not to remove fruits and vegetables from the area. A map of the quarantine zone is available online at

Residents are urged not to remove produce from the quarantine zone, and to consume homegrown fruits and vegetables onsite. 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 Mediterranean fruit fly, or “Medfly,” can infest over 260 types of fruits and vegetables, causing severe impacts on California agricultural exports and backyard gardens. A permanent infestation would result in estimated annual losses of $1.3 to $1.8 billion.

CDFA crews are already conducting eradication procedures in the area. Aerial release of sterile Medflies began on Friday, September 11, at a rate of 250,000 sterile flies per square mile. The release area is nine square miles at the core of the larger quarantine area. A map of the sterile fly release zone is available online at:

The 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, thereby preventing the females from producing 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.

Crews have also applied limited treatments to trees and plants in a 200-meter radius — about one-eighth of a mile — from the site where the mated fly was found. The substance being applied is the organic compound Naturalyte (active ingredient: spinosad), a naturally occurring extract from bacteria.

Naturalyte was used in the 2002-2003 Mexican fruit fly eradication program in the nearby community of Valley Center.

The eradication approach in Escondido 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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