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News Release

California Department of Food and Agriculture

Media Contacts: CDFA Public Affairs, (916) 654-0462,

California Department of Food and Agriculture
Release #18-063
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SACRAMENTO, October 12, 2018 -The California Department of Food and Agriculture (CDFA), the United States Department of Agriculture (USDA) and the San Mateo County Agricultural Commissioner’s office have eradicated a Mediterranean fruit fly (Medfly) infestation centered in and around the City of Half Moon Bay, ending a 56-square-mile quarantine that began November 24, 2017.
CDFA used the release of sterile male Medflies at a minimum rate of 500,000 flies per square mile per week as the mainstay of its eradication measures for this pest.  Additionally, properties within 200 meters of the detection sites were 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.
"This program demonstrates the value of biological approaches to invasive species," said CDFA Secretary Karen Ross. "In the 20-plus years we have released sterile Medflies in Southern California we have seen a dramatic reduction in infestations and quarantines and, of course, have shifted the focus of this long-term effort from pesticides to a more environmentally sound system.”

The eradication effort was in response to the detection of two wild Medflies. The sterile fly release program has a proven track record of eradication in California.  Sterile male flies mate with fertile 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 brought to California by the joint CDFA/USDA sterile insect rearing facility in Los Alamitos, California, which prepares sterile flies for release everyday over California.
USDA, CDFA and the San Mateo County Agricultural Commissioner acknowledge and thank local area residents for their cooperation in preventing the movement of backyard fruit and allowing property access to perform critical eradication activities.  Working together, we rid California of this invasive species.
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.  The eggs hatch into maggots and tunnel through the flesh of the fruit, making it unfit for consumption.
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 common pathway for these invasive species to enter the state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions of the world.  Help protect California’s agricultural and natural resources; please Don’t Pack a Pest ( when traveling or mailing packages.


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California Department of Food and Agriculture Office of Public Affairs
1220 N St., Ste. 214, Sacramento, CA 95814