Medfly Eradication Effort Proves Successful in Northern California

The California Department of Food and Agriculture (CDFA), USDA, Santa Clara County Agricultural Commissioner’s Office, and Alameda County Agricultural Commissioner’s Office have eradicated a Mediterranean fruit fly (Medfly) infestation centered in and around the City of San Jose, ending a 241-square-mile quarantine that began on Aug. 19, 2025. During that same month a year ago, a similarly sized Medfly infestation near Fremont, CA, was successfully eradicated.

CDFA used the release of sterile male Medflies at a minimum rate of 250,000 flies per square mile per week as the mainstay of its eradication measures for this pest. The sterile fly release program has a proven track record of eradication in California.

Additionally, properties within 200 meters of the detection sites were spot 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 breeding populations (maggots or mated females) were subject to host fruit and vegetable removal to eliminate eggs and larvae.

The Medfly is known to target more than 250 types of fruits and vegetables, potentially causing severe impacts on California agricultural exports and backyard gardens alike. Damage occurs when the female lays eggs inside the fruit, making it unfit for consumption.

To learn more about invasive fruit fly quarantines in California, visit cdfa.ca.gov/plant/fruitfly.