U.S. to Release Sterile Flies Over Texas and Mexico to Combat Screwworm

The U.S. Department of Agriculture (USDA) is ramping up efforts to control a dangerous livestock pest by releasing millions of sterile flies over Texas and Mexico, targeting the New World Screwworm (NWS), a flesh-eating maggot that threatens American agriculture.

According to the USDA, the flies will be sterilized using radiation and released by air, primarily in regions where Screwworm outbreaks have been reported. The goal is to disrupt the pest’s reproduction cycle, as sterile males will mate with wild females, resulting in eggs that do not hatch.

The NWS fly, found in parts of the Caribbean and South America, lays its eggs in wounds of warm-blooded animals. Once hatched, the larvae burrow into living flesh, often causing severe injury or death in livestock. The CDC warns that humans are also at risk in endemic areas, particularly those with open wounds or recent surgeries.

To scale the response, a new sterile fly production facility is slated to open in southern Mexico by July 2026. A U.S. distribution center in southern Texas is also expected by the end of next year, according to the USDA.

The sterile insect technique isn’t new. Between 1962 and 1975, the U.S. and Mexico released more than 94 billion sterile flies, ultimately eradicating the pest. Prior to that, the USDA estimated annual livestock losses of up to $100 million due to Screwworm infestations.

“This is a proven method,” said a USDA spokesperson. “The reestablishment of this infrastructure is essential to protecting American livestock and the agricultural economy.”

The renewed threat underscores the importance of cross-border cooperation. As in the past, success depends on coordinated surveillance, breeding, and fly distribution programs between the U.S. and Mexico.

While the sterile fly campaign targets livestock pests, health officials remind travelers to remain cautious.

The CDC states, “People who travel to these areas, spend time among livestock animals, sleep outdoors and have an open wound are at greater risk of becoming infested with NWS.”

The USDA plans to expand sterile fly releases in coming months, aiming to suppress the pest before it can gain a stronger foothold in U.S. territory.