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SACRAMENTO, August 21, 2025 – 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. If not stopped, Medflies can devastate fruits and vegetables grown in backyards and on local farms by reproducing and leaving larvae in produce, and the invasive flies can then spread to other regions. A quarantine is a way to minimize damage and stop the risk of spread by restricting the movement of fruits and vegetables.
CDFA 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.
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
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 not move homegrown produce from their property. However, residents living in the quarantine area may consume or process (i.e. juice, cook, or grind in the garbage disposal) fruit on the property where they were picked or dispose of fruit by bagging and sealing and placing 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.
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. The sterile medfly release program has a proven track record of eradication in California. 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. The sterile male medflies are reared at the joint CDFA/USDA sterile insect rearing facility in Los Alamitos, California, which prepares sterile flies for release everyday over California.
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.
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 each and every detected Medfly infestation in California 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 reportapest@cdfa.ca.gov.
While fruit flies and other invasive species that threaten California’s crops and natural environment are sometimes detected in agricultural areas, the vast majority are found in urban and suburban communities. The most likely pathway for these invasive species to enter our state are by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions of the world or from packages containing fruits and vegetable from other states or countries. To help protect California’s agriculture and natural resources, CDFA urges travelers to follow the Don’t Pack a Pest program guidelines (www.dontpackapest.com/).
To help prevent future introductions, residents are encouraged to:
- Assist agriculture crews working to protect your garden by allowing them access to your yard to place traps and inspect plants.
- When entering California from another state or country, avoid bringing agricultural products – including fruits and vegetables. Help us protect our agriculture, natural resources, and California’s unique biodiversity from invasive fruit flies – please Don’t Pack a Pest (www.dontpackapest.com/).
- Determine if your property is located within an active quarantine area by visiting www.CAFruitFly.com.
- Please do not send or receive any homegrown fruit, vegetables, or meat products, as they may contain invasive species that can “hitchhike” in these products.
- Inspect your garden regularly for signs of invasive fruit flies or maggots and report any findings to CDFA at 1-800-491-1899.
Federal, State and County agricultural officials work year-round to prevent, deter, and eliminate the threat of invasive pests and diseases that can damage or destroy our agricultural products, natural environment, resources, and unique biodiversity. The efforts are aimed at keeping California’s food supply plentiful, safe, and pest-free.
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.
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