Agriculture Secretary Brooke Rollins rides with USDA cattle fever tick riders along the U.S.-Mexico border June 18. (Courtesy USDA)

The USDA will release sterile New World screwworm male flies into Mexico from a deactivated Air Force base in south Texas, hoping to stop the cattle-biting parasite from crossing the border.

Agriculture Secretary Brooke Rollins announced June 18 plans for a $8.5 million renovation at Moore Air Base, 20 miles from the border. After the announcement, Rollins rode with USDA cattle fever tick riders, who patrol the border looking for stray and infected cattle.

Rollins said bolstering border security was one step in ramping up the battle to keep out New World screwworms.

“We have the proven tools, strong domestic and international partnerships, and the grit needed to win this battle,” she said.

New World screwworms (Cochliomyia hominivorax) corkscrew with sharp teeth into wounds or openings of animals and lay eggs. The parasite is endemic in the Caribbean and most of South America.

The parasite has been moving north through Mexico and has been detected 700 miles from the border. Two Texas federal lawmakers have introduced a bill authorizing the USDA to produce sterile flies in the U.S. to frustrate screwworm efforts to reproduce. The USDA already operates production facilities in Mexico and Panama.

“This is really important because ultimately what we’ll do is overwhelm these nasty little things with these sterile flies,” said Buck Wehrbein, president of National Cattlemen’s Beef Association and Nebraska cattleman.

The screwworm was largely eradicated in the U.S. in the 1960s, though an outbreak in Texas in 1976 cost producers $732 million ($1.8 billion in 2024 dollars), according to a report this month by the Congressional Research Service.

The U.S. and Mexico drove screwworms out of Mexico by 1986. The parasite, however, returned to southern Mexico last year and has been creeping north.

The USDA suspended live cattle, horse and bison imports from Mexico on May 11. Mexican authorities protested the border closure and said they were cooperating fully with the USDA.

Mexico typically accounts for more than 60% of imported cattle, about 1.25 million head a year. The border closure could increase retail beef prices, according to the congressional report.

The USDA said it recently spent $21 million to renovate a sterile-fly production facility capable of providing 60 to 100 million sterile flies a week in Metapa, Mexico. The USDA’s Panama facility is capable of producing more than 100 million sterile flies weekly.

U.S. Sen. John Cornyn and Rep. Tony Gonzales, both Republicans, introduced the STOP Screwworms Act to create a U.S. sterile-fly production facility. STOP stands for Strengthening Tactics to Obstruct the Population.

The USDA said it will also educate border-area residents to be aware of New World screwworms to create a “barrier zone of vigilance.”