Last month, the California Department of Food and Agriculture discovered two wild flies in Leimert Park, prompting the department to quarantine 69 square miles of Los Angeles County — an area that includes USC’s campus. 

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Ken Pellman, a public information officer for the L.A. County Department of Agricultural Commissioner/Weights and Measures, said there is an ongoing issue with the species identified in Leimert Park: the invasive Mediterranean fruit fly, also known as Medfly. The CDFA is releasing a quarter million sterile male Medflies per week to decrease the amount of Medfly offspring. The release is a nearly 200,000 fly increase from the 62,000 flies that are regularly released.

Brian Brown, curator of entomology at the Natural History Museum of L.A. County, said the Mediterranean Fruit Fly Preventive Release Program is a less toxic way of controlling fruit flies than traditional sprays. 

“Because of the general toxicity of the chemicals that they used to spray for these fruit flies, there was a lot of pressure to develop different methods for controlling them that weren’t so toxic,” Brown said. “They decided to develop a sterile male technique, where they rear up [fruit flies] and then, just before they hatch, irradiate them, which makes them totally unable to produce viable sperm.”

The sterile insect technique works as a form of birth control to decrease invasive species. Medfly are sterilized with gamma rays and X-rays, allowing them to mate but preventing them from producing offspring. 

The PRP quarantine only involves plant material, and requires certain fruit growers, sellers and residents eat produce on the property it was found and refrain from disposing of fruit anywhere other than the regular trash.

Pellman said the invasive flies arrive through uninspected plant materials that damage fruits and vegetables. He said the flies may be introduced to the area through individuals returning from a visit abroad or receiving out-of-state shipments of plant materials. 

Pellman said in order to prevent the invasive species from spreading, students and staff should have their fruits and vegetables officially inspected if they’ve traveled out of the country or got the produce in the mail.  

The invasive fruit flies pose a threat to more than 250 types of fruits and vegetables in California’s agriculture industry, according to a CDFA press release. As adult flies mate and create offspring, the larvae hatch into maggots, which damage the fruits and vegetables.

 The CDFA has used Medfly PRP since the program’s creation in 1996, and it is now standard protocol for controlling invasive species. Pellman said the method has proved effective and less intrusive to civilian lives than other methods, though it still comes with challenges. 

“Quarantines are never fun for the people who are subject to it,” Pellman said. “At the farmers markets, you might see some netting over the produce … You have more restrictions on what you could do when you’re a business that is involved in selling or growing produce.” 

Brown said it is imperative that those in the quarantine area comply with the implemented measures. The invasive fruit flies not only harm crops, but can also lead to financial losses as the amount of exported material decreases.

“If Medfly were to proliferate and become established, then you’re going to see a lot more use of pesticides …  smaller yields in California’s farms, less availability of fruits and vegetables [and] higher prices,” Pellman said.

The PRP requires a great amount of attention. The CDFA coordinates fly drops, which occur via airplane, with air traffic control to avoid interfering with regularly scheduled air traffic. 

Although there is no set timeline on how long the CDFA will release sterile fruit flies, officials said they hope they don’t find any more Medfly specimens so the clock won’t have to reset.

“If you don’t keep up to date with going after these flies when populations pop up here and there, inevitably, they could have to start from scratch and dump out sterile males in huge numbers which becomes really expensive,” Brown said.