State, local and federal agriculture officials have eradicated a Mediterranean fruit fly (Medfly) infestation centered in and around the City of San Jose, California. The eradication ends a 241-square-mile quarantine that began on Aug. 19, 2025. The California Department of Food and Agriculture (CDFA), the U.S. Department of Agriculture (USDA), and the Santa Clara County and Alameda County agricultural commissioner’s offices achieved the eradication.
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. Sterile male flies mate with fertile female flies in the natural environment but produce no offspring, decreasing the overall fly population.
Additionally, properties within 200 meters of the detection sites were spot-treated with an organic formulation of spinosad. Spinosad, which originates from naturally occurring bacteria in soil, was applied to eliminate any mated females and reduce the density of the population. To further reduce the pest 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 (including citrus) and vegetables, potentially causing severe impacts on California agricultural exports. Damage occurs when the female lays eggs inside the fruit, making it unfit for consumption.
While Santa Clara County’s Medfly quarantine has ended, the ongoing threat of new infestations by non-native species remains. Invasive fruit flies and other invasive species can endanger the state’s agriculture and natural resources, as well as homegrown fruits and vegetables.
Learn more about invasive species and how to protect California’s fruits and vegetables here.
Source: CDFA
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