The U.S. Department of Agriculture is reviving a proven sterile-insect technique to contain the renewed spread of the flesh-eating New World Screwworm fly along the U.S.–Mexico border. The agency plans to breed and air-drop billions of radiation-sterilised male flies over southern Mexico and southern Texas so they mate with wild females, producing eggs that do not hatch and gradually collapsing the pest population.
To meet the scale required, the USDA will convert an existing fruit-fly plant in southern Mexico into a screwworm facility by July 2026 at a cost of about $21 million and build an $8.5 million distribution centre in southern Texas before year-end. Combined with output from an established plant in Panama, the programme aims to reach a weekly capacity of roughly 400 million sterile males—more than triple current production.
The strategy mirrors the 1962-1975 campaign that released 94 billion sterile flies and eliminated the parasite north of Panama. Left unchecked, screwworm larvae burrow into the wounds of cattle, wildlife, pets and, on rare occasions, humans; veterinarians warn a 1,000-pound steer can die within two weeks of infestation. In the 1950s and 1960s the pest cost U.S. ranchers an estimated $50 million to $100 million annually.
Detection of the fly in southern Mexico late last year prompted the USDA in May to suspend imports of live cattle, horses and bison at southern border crossings, a restriction that is expected to last at least until mid-September. Officials say the expanded sterile-fly campaign is essential for lifting those controls and protecting the $113 billion U.S. cattle industry.
The air-drop method is not without hazards: a plane releasing sterile flies crashed near the Mexico-Guatemala border in June, killing three people. Even so, entomologists describe the sterile-insect technique as one of the agency’s most effective tools, calling it “an all-time great” example of science solving a large-scale agricultural threat.
