With US Cattle at Risk, Texas Breaks Out the Flies stopping spawn from crossing the Mexican border and wreaking havoc on the American cattle industry

The first U.S.-based center in decades for releasing sterile screwworm flies opened Monday in Texas, marking a major step in preventing the destructive parasite from crossing the Mexican border and threatening the American cattle industry.

U.S. Agriculture Secretary Brooke Rollins joined Texas Gov. Greg Abbott at a former Air Force base near Edinburg, Texas, to unveil the new facility, according to the Associated Press. The site will allow officials to release millions of sterile male New World screwworm flies, which are currently bred in Mexico or Panama, on both sides of the border.

The U.S. Department of Agriculture is also planning a $750 million facility nearby to breed sterile flies domestically, though Rollins said that plant is not expected to be completed until late 2027. In the meantime, the USDA is investing $21 million to convert an existing fruit fly breeding center in southern Mexico into one dedicated to screwworm flies starting this summer.

The strategy relies on sterile male flies mating with wild females, which typically mate only once during their several-week lifespan. Because the males are sterile, the females’ eggs—often laid in open wounds or mucous membranes—do not hatch into flesh-eating maggots. These larvae can infest livestock, wildlife, pets, and even humans.

“It’s a real testament to the all-hands-on-deck effort that we do not have the pest in our country yet,” Rollins said.

In November, the USDA opened a fly release site in Tampico, Mexico, using flies bred in Panama. However, that location sits roughly 330 miles south of the U.S.–Mexico border. “We knew we needed a short-term, gap-filling solution, which is exactly what we are cutting a ribbon on today,” Abbott said.

Mexico’s cattle industry has suffered significant damage from screwworm infestations, prompting the U.S. to close the border since July to imports of cattle, bison, and horses.

A similar sterile fly program had nearly eliminated the pest from the United States by the early 1970s. The only notable exceptions were a brief outbreak in the Florida Keys in 2017 and a recent incident involving a horse imported from Argentina into Florida that required treatment before entry, Rollins noted.

After the pest was eradicated domestically, U.S. fly-breeding facilities were shut down, leaving Panama as the only site in the Western Hemisphere producing sterile males. That facility can produce about 117 million flies per week. The new Texas breeding plant, once completed, is designed to produce up to 300 million flies weekly.