Santa Clara County Under Quarantine for the Mediterranean Fruit Fly, Millions of Medflies Scheduled For Released

A portion of Santa Clara County has been placed under quarantine for the Mediterranean fruit fly (Medfly) following the detection of two wild female flies in the city of San José.

According to a media release by the California Department of Food and Agriculture Office of Public Affairs (CDFA) on August 21, 2025, if not stopped, Medflies can devastate fruits and vegetables by reproducing and leaving larvae in produce.

The quarantine area measures approximately 109 square miles, bordered on the north by Trade Zone Boulevard; on the south by Camden Avenue; on the west by San Tomas Expressway; and on the east by Evergreen Valley Community College. 

The quarantine will cover parts of the cities of San José, Santa Clara, Campbell, and the town of Los Gatos. A link to the quarantine map may be found here: www.cdfa.ca.gov/plant/medfly/regulation.html.

Sterile male Medflies are scheduled to be released in the area as part of the eradication effort. The release rate will be 250,000 males per square mile per week in an 84.76 square mile area around the infestation. 

Sterile male flies mate with fertile wild female flies in the natural environment but produce no offspring. The fly 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.

Additionally, properties within 200 meters of the detection sites are treated with an organic formulation of Spinosad, which originates from naturally occurring bacteria in soil, to eliminate any mated females and reduce the density of the population.

To further reduce the population, properties within 100 meters of infested properties are subject to host-plant or fruit removal to eliminate eggs and larvae.

Furthermore, the invasive flies can then spread to other regions outside the San Francisco Bay Area.

CDFA wrote that it is working collaboratively with the United States Department of Agriculture (USDA) and the Santa Clara County Division of Agriculture on this project. This project is new and separate from the recently eradicated Medfly infestation in Alameda County, CA.

The quarantine will affect any growers, wholesalers, and retailers of susceptible fruit in the area, as well as residents. Home gardeners are urged not to move homegrown produce from their property.

However, residents living in the quarantine area may consume or process fruit on the property where they were picked or dispose of fruit by bagging and sealing it and placing it in the garbage (not green waste).  

These actions protect against the artificial spread of the infestation to nearby regions where it can affect California's food supply and backyard gardens.

The media statement confirms this eradication approach is the standard Medfly program used by CDFA and is the safest, most effective, and most efficient response program available. CDFA has successfully eradicated every detected Medfly infestation in California's history, dating back more than 40 years.

The pest is known to target more than 250 types of fruits and vegetables. Damage occurs when the female lays eggs inside the fruit. The eggs hatch into maggots, which tunnel through the flesh of the fruit, making it unfit for consumption. 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 or email [email protected].

Residents with questions about the project may call CDFA's Pest Hotline at 1-800-491-1899. To learn more about invasive species and how to protect California's fruits and vegetables, please visit www.cdfa.ca.gov/plant/fruitfly.