TOPEKA, Kan. — The U.S. government is launching an ambitious plan to combat a harmful fly species known to ravage livestock by breeding billions of flies and releasing them over parts of Mexico and southern Texas. This initiative, aimed at defending the beef industry and protecting wildlife, echoes a successful technique employed decades earlier in eradication efforts.
At the heart of this strategy is the New World Screwworm fly, whose larvae feed on living flesh, inflicting serious harm on cattle and other warm-blooded animals. As concerns rise over the recent resurgence of this pest in southern Mexico, the U.S. Department of Agriculture is preparing to significantly increase the production of sterile male flies, which will be irradiated before their release. When these males mate with wild females, the resulting eggs remain unfertilized, gradually reducing the fly population.
Experts like Edwin Burgess, a parasitology researcher at the University of Florida, describe this method as a breakthrough in pest control. “It’s a classic case of using science to address a significant agricultural challenge,” he remarked, highlighting the approach’s past success.
The New World Screwworm fly thrives in warmer climates, making southern regions particularly vulnerable. Females prefer to lay their eggs in wounds, leading to rapid infestations. Veterinarians can treat infested animals, but the distress caused by the larvae is considerable. Michael Bailey, president elect of the American Veterinary Medicine Association, noted how quickly a large animal could succumb to an infestation.
To prepare for the new breeding efforts, the USDA anticipates opening a sterile fly factory in southern Mexico by July 2026, along with a distribution center in southern Texas by year’s end. Historical records show that from 1962 to 1975, the U.S. and Mexico released over 94 billion sterile flies to eliminate the pest, marking a significant victory in agricultural pest control.
The numbers required for effective mating are substantial. Female screwworm flies mate just once during their adult lifespan, prompting officials to breed enough sterile males to dominate the reproductive landscape. This reliance on the flies’ biological traits gives researchers a unique advantage in regulating the population.
In response to the recent emergence of screwworms in the region, the U.S. temporarily suspended imports of certain live animals in May, a ban expected to last until mid-September. The primary concern extends beyond livestock—these flies will also target pets and even humans.
Breeding facilities, like the one envisioned in Texas, will utilize advanced methods to produce large quantities of sterile flies. The original breeding programs relied on a mix of horse meat and honey, evolving to incorporate ingredients like egg powder and blood plasma to ensure larvae receive essential nutrients.
Releasing flies from airplanes is part of the plan, although it comes with risks. In a tragic incident last month, a plane engaged in fly deployment crashed near the Mexican border, resulting in multiple fatalities. The fly distribution strategy has roots in the testing phases of the 1950s and 1960s, where scientists innovatively packaged the flies for aerial release.
As scientists and agriculture officials reflect on the long-term viability of this approach, some advocate for maintaining and expanding breeding facilities to guard against any resurgence of the pest. Burgess emphasized the importance of vigilance, warning that complacency could lead to a repeat of past infestations.
The battle against the New World Screwworm fly illustrates the complex intersection of science and agriculture, with implications that reach far beyond livestock to affect ecosystems and livelihoods.