The New World Screwworm Threat
The U.S. government has announced plans to breed billions of sterile flies at a South Texas fly factory to combat the New World screwworm, a flesh-eating maggot capable of devastating the state’s cattle industry. The screwworm is a significant threat to the livestock industry, and the government is taking aggressive steps to prevent its spread.
The Threat of the New World Screwworm
The New World screwworm is a fly that burrows into open wounds of animals and deposits larvae, causing significant harm and even death. The pest has spread through Central America, reaching as far north as Oaxaca and Veracruz, Mexico, roughly 700 miles from the Texas-Mexico border. Federal and state officials warn that the insect has the potential to devastate the state’s $15 billion cattle industry, send beef prices soaring, and kill wildlife. It can also deposit its larvae on pets and humans.
Construction of the Fly Factory
Construction will begin on a $750 million facility in the Rio Grande Valley town of Edinburg, U.S. Agriculture Secretary Brooke Rollins announced. When complete, the facility will be capable of producing 300 million sterile flies a week, tripling the current output. The new facility will complement an $8.5 million fly dispersal facility also being built in Edinburg. In addition, the U.S. plans to spend $100 million to identify and deploy new technologies, such as traps and lures, to fight the pest.
U.S. Secretary of Agriculture Brooke Rollins discusses measures for dealing with the New World screwworm during a press conference with Texas Gov. Greg Abbott, not pictured, held at the Texas Capitol, Friday, Aug. 15, 2025, in Austin, Texas. (AP Photo/Rodolfo Gonzalez)
History of the New World Screwworm
Screwworms were once an annual scourge for cattle ranchers and dairy farmers, particularly in the Southeast. The pests were considered eradicated in the U.S. in the 1960s, but they have continued to pop up. In 2016, a screwworm infestation killed endangered deer in Florida.
Response Efforts
In June, Texas Gov. Greg Abbott directed the Texas Animal Health Commission and Texas Parks and Wildlife Department to form the Texas New World Screwworm Response Team to coordinate communications and the state’s preparedness and response efforts. The governor said the pests pose a danger to the entire country, but that Texas and other border states are on the front lines of the fight.
“This could result in billions of dollars in losses a year,” he said. “It could truly crush the cattle industry and livestock industry in Texas.”
Fighting the Pest
To fight the pests, sterile male flies will be dropped from airplanes over Mexico to mate with fertile females, which mate only once in their weekslong adult lives, producing nonviable eggs until the population dies.
A New World screwworm larvae sits at rest in this undated photo.
The Texas facility would be one of just three in the world. A factory in Panama now produces about 117 million flies per week. Another facility in southern Mexico is being renovated to produce an additional 60 to 100 million sterile flies per week, with a $21 million investment from the U.S.
In July, the U.S. suspended all imports of live cattle, horses, and bison through U.S. ports of entry along the southern border, a move criticized by Mexico’s President Claudia Sheinbaum, who suggested the U.S. was exaggerating the threat to its beef industry. Rollins said imports will only be accepted after the screwworm is pushed back.
“Without these very, very aggressive steps, the screwworm would have gotten to our border already and would already be in our country,” Rollins said. “We’re doing everything we can to stop it.”
Conclusion
The New World screwworm poses a significant threat to the livestock industry, and the government is taking aggressive steps to prevent its spread. The construction of the fly factory in South Texas and the deployment of sterile male flies are crucial measures to combat the pest.
