Santa Clara County Medfly infestation eradicated, ending 11-month quarantine

A Mediterranean fruit fly infestation has been eradicated, ending an almost yearlong quarantine in San Jose and surrounding areas, according to a news release Monday.

The Medfly targets more than 250 types of fruits and vegetables by laying eggs inside them that hatch into maggots, which make the produce inedible. The news release stated that they can severely impact California agricultural exports and backyard gardens alike. The California Department of Food and Agriculture (CDFA) reported that the state could lose up to $1.8 billion per year if Medfly populations are left unchecked.

The quarantine began last August and spanned a 241-square-mile area that included parts of San Jose, Los Gatos, Campbell and Santa Clara. The quarantine prevented the transportation of vulnerable produce varieties among retailers, wholesalers and growers to “minimize damage and stop the risk of spread,” according to CDFA.

The U.S. Department of Agriculture (USDA), CDFA and the agricultural commissioner’s offices in Santa Clara and Alameda counties worked together to address the Medfly infestation. CDFA and USDA spawned sterile male Medflies in an insect-rearing facility in Los Alamitos. They released at least 250,000 flies per square mile per week to eradicate the Medfly population. The sterile male flies mated with fertile female flies, but the interactions didn’t produce offspring, decreasing the overall fly population. According to Jason Leathers, CDFA branch chief for Pest Detection/Emergency Projects, Medflies were first found in California in Los Angeles. In the 50 years since then, they have been found 38 times and successfully eradicated each time.

Properties within 200 meters of the detection sites were spot treated with an organic formulation of Spinosad, a biological insecticide derived from naturally occurring bacteria in soil, to kill any mated females and reduce the density of the population. Further population control efforts included host fruit and vegetable removal at properties within 100 meters of breeding populations to kill eggs and larvae.

Although the Medfly quarantine has ended, there is still a threat of new infestations by non-native species, such as invasive fruit flies and other species. Agricultural officials asked residents to help prevent future introductions of invasive species by allowing agriculture crews access to yards to place traps and inspect plants and conduct their own inspections for signs of invasive fruit flies or maggots. They also said not to bring fruits and vegetables into California from another state or country and not to send or receive any homegrown fruit, vegetables or meat products that may contain invasive species that “hitchhike” in these products. Residents can report any unusual findings to CDFA at 1-800-491-1899.