NATIONAL NEWS

The US plans to begin breeding billions of flies to fight a pest. Here is how it will work

Jul 1, 2025, 8:51 PM

In this Jan. 2024 photo provided by The Panama-United States Commission for the Eradication and Pre...

In this Jan. 2024 photo provided by The Panama-United States Commission for the Eradication and Prevention of Cattle Screwworms (COPEG), a worker drops New World screwworm fly larvae into a tray at a facility that breeds sterile flies in Pacora, Panama. (COPEG via AP)
Credit: ASSOCIATED PRESS

(COPEG via AP)

TOPEKA, Kan. (AP) — The U.S. government is preparing to breed billions of flies and dump them out of airplanes over Mexico and southern Texas to fight a flesh-eating maggot.

That sounds like the plot of a horror movie, but it is part of the government’s plans for protecting the U.S. from a bug that could devastate its beef industry, decimate wildlife and even kill household pets. This weird science has worked well before.

“It’s an exceptionally good technology,” said Edwin Burgess, an assistant professor at the University of Florida who studies parasites in animals, particularly livestock. “It’s an all-time great in terms of translating science to solve some kind of large problem.”

The targeted pest is the flesh-eating larva of The U.S. Department of Agriculture plans to ramp up the breeding and distribution of adult male flies — sterilizing them with radiation before releasing them — so they can mate ineffectively with females and over time cause the population to die out.

It is more effective and environmentally friendly than spraying the pest into oblivion, and it is how the U.S. and other nations north of Panama eradicated the same pest decades ago. Sterile flies from a factory in Panama kept the flies contained there for years, but the pest appeared in southern Mexico late last year.

The USDA expects a new screwworm fly factory to be up and running in southern Mexico by July 2026. It plans to open a fly distribution center in southern Texas by the end of the year so that it can import and distribute flies from Panama if necessary.

Fly feeds on live flesh

Most fly larvae feed on dead flesh, making the New World screwworm fly and its Old World counterpart in Asia and Africa outliers — and for the American beef industry, a serious threat. Females lay their eggs in wounds and, sometimes, exposed mucus.

“A thousand-pound bovine can be dead from this in two weeks,” said Michael Bailey, president elect of the American Veterinary Medicine Association.

Veterinarians have effective treatments for infested animals, but an infestation can still be unpleasant — and cripple an animal with pain.

Don Hineman, a retired western Kansas rancher, recalled infected cattle as a youngster on his family’s farm.

“It smelled nasty,” he said. “Like rotting meat.”

How scientists will use the fly’s biology against it

The New World screwworm fly is a tropical species, unable to survive Midwestern or Great Plains winters, so it was a seasonal scourge. Still, the U.S. and Mexico bred and released more than 94 billion sterile flies from 1962 through 1975 to eradicate the pest, according to the USDA.

The numbers need to be large enough that females in the wild can’t help but hook up with sterile males for mating.

One biological trait gives fly fighters a crucial wing up: Females mate only once in their weekslong adult lives.

Why the US wants to breed more flies

Alarmed about the fly’s migration north, the U.S. temporarily closed its southern border in May to imports of live cattle, horses and bison and it won’t be fully open again at least until mid-September.

But female flies can lay their eggs in wounds on any warm-blooded animal, and that includes humans.

Decades ago, the U.S. had fly factories in Florida and Texas, but they closed as the pest was eradicated.

The Panama fly factory can breed up to 117 million a week, but the USDA wants the capacity to breed at least 400 million a week. It plans to spend $8.5 million on the Texas site and $21 million to convert a facility in southern Mexico for breeding sterile fruit flies into one for screwworm flies.

How to raise hundreds of millions of flies

In one sense, raising a large colony of flies is relatively easy, said Cassandra Olds, an assistant professor of entomology at Kansas State University.

But, she added, “You’ve got to give the female the cues that she needs to lay her eggs, and then the larvae have to have enough nutrients.”

Fly factories once fed larvae horse meat and honey and then moved to a mix of dried eggs and either honey or molasses, according to past USDA research. Later, the Panama factory used a mix that included egg powder and red blood cells and plasma from cattle.

In the wild, larvae ready for the equivalent of a butterfly’s cocoon stage drop off their hosts and onto the ground, burrow just below the surface and grow to adulthood inside a protective casing making them resemble a dark brown Tic Tac mint. In the Panama factory, workers drop them into trays of sawdust.

Security is an issue. Sonja Swiger, an entomologist with Texas A&M University’s Extension Service, said a breeding facility must prevent any fertile adults kept for breeding stock from escaping.

How to drop flies from an airplane

Dropping flies from the air can be dangerous. Last month, a plane freeing sterile flies crashed near Mexico’s border with Guatemala, killing three people.

In test runs in the 1950s, according to the USDA, scientists put the flies in paper cups and then dropped the cups out of planes using special chutes. Later, they loaded them into boxes with a machine known as a “Whiz Packer.”

The method is still much the same: Light planes with crates of flies drop those crates.

Burgess called the development of sterile fly breeding and distribution in the 1950s and 1960s one of the USDA’s “crowning achievements.”

Some agriculture officials argue now that new factories shouldn’t be shuttered after another successful fight.

“Something we think we have complete control over — and we have declared a triumph and victory over — can always rear its ugly head again,” Burgess said.


National News

Associated Press

Authorities search for a woman who got off a cruise ship in Alaska to hike and didn’t return

JUNEAU, Alaska (AP) — Authorities were searching for a woman visiting Alaska’s capital city who did not return to her cruise ship from a hike she said she was taking, officials said Wednesday. The Juneau Police Department said it received a report Tuesday afternoon that the 62-year-old from Kentucky, who told relatives that morning that […]

1 hour ago

Brian Kohberger, charged in the murders of four University of Idaho students, appears at the Ada Co...

Associated Press

A Q-Tip and spotless car were key evidence linking Bryan Kohberger to murders of 4 Idaho students

BOISE, Idaho (AP) — The lead prosecutor tasked with finding justice for four University of Idaho students killed in a grisly quadruple stabbing more than two years ago laid out his key evidence Wednesday at a court hearing for Bryan Kohberger, who agreed to plead guilty earlier this week to avoid the death penalty. The […]

2 hours ago

FILE - Marc Agnifilo, attorney for Sean "Diddy" Combs, arrives at Manhattan federal court, Tuesday,...

Associated Press

Photos of celebrity trials that have garnered wide-spread attention

A New York City jury convicted Sean “Diddy” Combs on prostitution-related charges but acquitted him of sex trafficking and racketeering. The case joins a list of high-profile celebrity trials, including those of O.J. Simpson, Michael Jackson, Harvey Weinstein and Alec Baldwin, that have captured public attention. ___ This is a photo gallery curated by AP […]

2 hours ago

Defense attorney Carl Arnold speaks during a hearing on claims of juror misconduct in the jailhouse...

Associated Press

Judge denies bid by the suspect in Tupac Shakur’s killing for a new trial in a jailhouse fight

LAS VEGAS (AP) — Duane “Keffe D” Davis, who is awaiting trial in the 1996 killing of rap icon Tupac Shakur, has lost a bid for a new trial in a separate battery case tied to a jailhouse fight. The ruling came Wednesday after a tense hearing in a Las Vegas courtroom that underscored the […]

2 hours ago

Associated Press

Small skydiving aircraft goes off runway in New Jersey, sending at least 5 to hospital

MONROE TOWNSHIP, N.J. (AP) — At least five people were taken to a hospital when a small skydiving aircraft went off the end of a runway at an airport in New Jersey on Wednesday evening, according to authorities. The incident at the Cross Keys Airport involved a Cessna 208B carrying 15 people, according to a […]

3 hours ago

FILE - A nurse loads a syringe with a COVID-19 booster vaccine at an inoculation station in Jackson...

Associated Press

FDA vaccine official restricted COVID vaccine approvals against the advice of agency staff

WASHINGTON (AP) — The government’s top vaccine official working under Health Secretary Robert F. Kennedy Jr. recently restricted the approval of two COVID-19 vaccines, disregarding recommendations from government scientists, according to federal documents released Wednesday. The new memos from the Food and Drug Administration show how the agency’s vaccine chief, Dr. Vinay Prasad, personally intervened […]

3 hours ago

The US plans to begin breeding billions of flies to fight a pest. Here is how it will work