TOPEKA, Kan. (news agencies) — 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 New World Screwworm fly. 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. They mate with females in the wild, and the eggs laid by the female aren’t fertilized and don’t hatch. There are fewer larvae, and over time, the fly population dies 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.
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.”
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.
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.
