USDA’s Sterile Flies Program Targets Screwworm Threat
The sterile flies USDA initiative is ramping up after the flesh-eating New World screwworm fly was detected moving north through Mexico, posing a devastating threat to the U.S. beef industry, wildlife, and even pets. The USDA will breed billions of sterile male flies, irradiate them to ensure they cannot reproduce, and release them from planes over southern Texas and Mexico.
This method forces wild female screwworm flies to mate with sterile males, causing the population to collapse over time.
Proven Technology for Parasite Control
Experts like Edwin Burgess from the University of Florida say the sterile flies USDA strategy is one of the greatest examples of applied science solving a massive agricultural problem.
“It’s an exceptionally good technology,” Burgess noted. “An all-time great in terms of translating science to solve a large problem.”
The approach previously eradicated screwworms from the U.S. and all areas north of Panama after the U.S. and Mexico released 94 billion sterile flies between 1962 and 1975.
Massive Breeding Effort Underway
The USDA currently uses a fly factory in Panama, producing 117 million sterile flies per week. But officials want a capacity of at least 400 million weekly, prompting plans to open a new $21 million breeding facility in southern Mexico by July 2026 and a $8.5 million distribution center in Texas by year’s end.
This sterile flies USDA expansion is critical because the pest was detected in southern Mexico late last year, raising alarms about a possible northward spread.
Why Screwworms Are So Dangerous
The New World screwworm fly is unique among maggots: rather than feeding on dead flesh, its larvae consume living tissue. Female flies lay eggs in open wounds or mucus membranes of warm-blooded animals.
“A thousand-pound bovine can be dead from this in two weeks,” warned Michael Bailey of the American Veterinary Medicine Association.
While veterinarians can treat infections, infestations cause extreme pain, severe wounds, and even death in livestock and pets.
Historical Success and New Challenges
Screwworms were once a seasonal scourge in the U.S., with fly factories in Florida and Texas keeping populations under control until eradication programs succeeded decades ago. But closing those facilities left North America vulnerable to re-infestation.
This time, USDA officials argue new factories should remain operational even after screwworms are eradicated to prevent future outbreaks.
“Something we think we have complete control over can always rear its ugly head again,” Burgess emphasized.
How the Sterile Fly Strategy Works
Female screwworm flies mate only once during their short adult lives. By flooding the environment with sterile males, nearly all matings become unproductive, quickly crashing the pest population.
Fly factories breed larvae in specialized facilities, historically feeding them mixtures of egg powder, honey, molasses, and cattle blood products. Once larvae mature, they’re irradiated to sterilize them, then packed into crates.
Planes drop these crates over targeted areas, similar to methods used since the 1950s, when scientists first dropped flies from paper cups and then boxes with devices nicknamed “Whiz Packers.”
Risks and Precautions
Security remains a top concern at breeding facilities to ensure no fertile flies escape. Additionally, releasing flies from airplanes carries hazards: last month, a plane conducting a sterile fly drop crashed near Mexico’s border with Guatemala, tragically killing three people.
Protecting the Future of U.S. Agriculture
The sterile flies USDA program is seen as a vital investment in safeguarding American agriculture. As the USDA scales up operations, officials hope to keep screwworms confined and protect billions of dollars’ worth of livestock and wildlife.
