Dec 19, 2017

Medflies found in California’s San Mateo County; quarantine issued

Part of California’s San Mateo County has been placed under quarantine for the Mediterranean fruit fly, or Medfly, following the detection of two Medflies in the city of Half Moon Bay.

The California Department of Food and Agriculture (CDFA) is working with the USDA and the San Mateo County Agricultural Commissioner’s office on this project.

The quarantined area measures 56 square miles. The area is bordered on the north by San Vicente Creek, on the south by Lobitos Creek Road, on the west by the Pacific Ocean, and on the east by Lower Crystal Springs Reservoir.

Other medfly quarantines are active near Los Angeles and in Solano County, according to a map on the CDFA website.

Sterile male Medflies will be released in the area as part of the eradication effort. The release rate will be 500,000 males per square mile per week in a 12 square mile area around the infestation.  In addition, properties within 200 meters of detection sites are being treated with an organic formulation of Spinosad, which originates from naturally-occurring bacteria.

Sterile male Medflies are provided by the joint CDFA/USDA sterile insect rearing facility in Los Alamitos, which prepares sterile files for release every day over the Los Angeles basin. The sterile release program has a proven track record of success in California. Sterile male flies mate with fertile female flies in the natural environment but produce no offspring. The Medfly population decreases as the wild flies reach the end of their natural lifespan with no offspring to replace them, ultimately resulting in the eradication of the pest.

The quarantine will affect any growers, wholesalers, and retailers of susceptible fruit in the area as well as nurseries that grow and sell Medfly host plants. The quarantine will also affect local residents – home gardeners are urged to consume homegrown produce on site and not move it from their property.  These actions protect against the artificial spread of the infestation.

The Medfly can infest more than 250 types of fruits and vegetables, causing severe impacts on California agricultural exports and backyard gardens alike.  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.

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 our state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions of the world.

CDFA urges travelers to follow guidelines in its Don’t Pack a Pest program.

Above is a dorsal view of an adult male Mediterranean fruit fly, Ceratitis capitata(Wiedemann). Photograph by Scott Bauer, USDA.