Millions of sterile fruit flies are being released in California: Here's why.

USA Today

07-05-2025

Millions of sterile fruit flies are being released in California: Here's why.
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Environmental officials in California's San Francisco Bay and East Bay areas are releasing millions of sterile fruit flies to reduce the number of pests leading to produce decay.
The fruit flies will be released in parts of Alameda and Santa Clara counties, the California Department of Food and Agriculture said in an email to USA TODAY on May 7.
The sterile fruit flies will be released due to an infestation of the Mediterranean fruit fly, also known as the Medfly, the department said.
Calling the Medfly "an invasive pest," the department said the fly threatens over 250 types of produce. The Medfly can damage fruits and vegetables in backyard gardens, as well as agricultural products grown throughout the state.
The sterile fruit flies are part of the Sterile Insect Technique, and will disrupt the natural mating cycle of the Medfly, officials said, adding that the sterile flies will mate with wild females, leading to no offspring and reducing the number of Mediterranean fruit flies.
The department is working with the U.S. Department of Agriculture to release the flies.
"Millions of sterile fruit flies are being released each week by private aircraft and pilots," said Rodney Farol, an agricultural technician with the California Department of Food and Agriculture, in a video about the project.
"It's safe, precise, and environmentally-friendly, eliminating MedFlies without harsh chemicals," he added.
Where are the flies being released?
The sterile fruit flies will be released in two quarantine areas: Alameda and Santa Clara counties.
The Mediterranean fruit fly is "one of the most damaging agricultural pests in the world," according to the Animal & Plant Health Inspection Service, an office within the USDA. The flies can infest fruits, nuts and vegetables, making them inedible.
The first among U.S. mainland Medfly infestations was in 1929 in Florida, the service said. The Medfly has been documented in the Mediterranean region, Southern Europe, the Middle East, Western Australia, South and Central America and Hawaii.
According to the service, Medfly eggs are white, small and elongated. The larvae, or maggots, feed inside the fruit. Once the Medfly gets to produce, it decays and falls to the ground, while larvae develop and feed on the pulp.
According to Farol, from the California Department of Food and Agriculture, residents can do the following during this process:
Buy produce and plants only from local, licensed retailers and nurseries
Leave homegrown fruits and vegetables where they are
Inspect homegrown produce
If you see signs of fruit flies or maggots, call the pest hotline at 1-800-491-1899
And the Animal & Plant Health Inspection Service said on its website that Californians can prevent the spread of the Medfly by:
Only bringing fresh fruits, vegetables, or plants into your state if agricultural inspectors have cleared them first
Declaring all agricultural products to U.S. customs officials when returning from international travel
Double-bagging fruits and vegetables in plastic bags before throwing them away
Residents can learn more at www.cdfa.ca.gov/plant/fruitfly.
Saleen Martin is a reporter on USA TODAY's NOW team. She is from Norfolk, Virginia – the 757. Email her at [e-mail].