New Mexfly Quarantine for California

Josh McGillCalifornia Corner, Pests, Regulation

A portion of San Diego County in California has been placed under a quarantine for the Mexican fruit fly (Mexfly). The quarantine follows the detection of six flies and one larva in and around the unincorporated area of Valley Center.


The quarantine will affect any growers, wholesalers, nurseries and retailers of host fruit or host plants in the area. The U.S. Department of Agriculture, the San Diego County Agricultural Commissioner and the California Department of Food and Agriculture (CDFA) are working collaboratively on this project.

The quarantine area in San Diego County measures 77 square miles. It is bordered on the north by Wilderness Gardens Preserve, on the south by the Lake Wohlford Park, on the west by Moosa Canyon and on the east by Hellhole Canyon Preserve. See the quarantine map here.

The Mexfly can lay its eggs in and infest more than 50 types of fruits and vegetables, including citrus, avocados and tropical fruits.

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

As part of the eradication effort, approximately 250,000 sterile Mexfly males will be released per square mile, per week, in an area of 43 square miles around the infestation. Sterile male flies will mate with fertile, wild female flies but produce no offspring. This reduces the Mexican fruit fly population as wild flies reach the end of their natural life span with no offspring to replace them, ultimately resulting in the eradication of the pest. This eradication approach is the standard program used by CDFA.

In addition, properties within 200 meters of the detections are being treated with an organic formulation of spinosad, which originates from naturally occurring bacteria, to remove any live fruit flies and reduce the density of the population. Fruit will also be removed from host plants within 100 meters of properties with larval detections and/or female fly detections.

Questions may be addressed to CDFA’s Pest Hotline at 800-491-1899. Additional information about the Mexfly can be found here.

Source: Citrus Pest & Disease Prevention Program

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