A flesh-eating fly is back in South Texas. It was gone for 50 years. Now scientists want to use its own bad smell against it.

Researchers at Colorado State University are studying a foul smell. That smell pulls New World Screwworm flies to open cuts on animals. The fly lays eggs in wounds. The eggs turn into maggots. The maggots eat living flesh, not just dead flesh like most maggots do. That is why ranchers call it flesh-eating. The study wants to find the exact smell that draws the flies in. Traps could use that smell as bait.

This news matters a lot in South Texas. Screwworm has hit cattle, sheep, goats and dogs in Texas and New Mexico this year. Ranching is a big part of life along the border. A bigger outbreak could hurt herds and family ranches near home.

Professor Jessica Metcalf leads the study. She works at Colorado State University. Her team has five other scientists. They are Kayla Borton, Kelly Wrighton, Anthony Grigsby, Valerie Seitz and Tracey Goldstein. The team works with a group called the Colorado State Microbiome Network. Together they study germs found in animal wounds.

The team checks gases made by germs in fresh wounds. These gases are called volatile organic compounds. In plain words, they are just smelly chemicals made by germs. The team checks smells from live wounds. Then they check smells from dead animal flesh. They also study a look-alike fly called the secondary screwworm. That fly does not eat living flesh. Comparing the two flies helps show what makes the real screwworm zero in on a wound.

"We use these bacterial cues to stay away," Metcalf said. "The insects are using them for a different reason. They're like, 'Yes, bring it.'"

Ranchers, vets and wildlife workers are helping the study. They collect wound samples out in the field. The work is part of a bigger pot of money. The USDA gave $105 million total for 40 screwworm projects. Metcalf's study is just one of those 40 projects. It did not get the full $105 million alone. The team is still working to find the exact smell mix. No final trap bait has come out yet.

The study will also check one more thing. For years, the government has fought screwworm with sterile male flies. These lab-raised flies cannot father new maggots. Releasing millions of them empties out the wild fly population over time. Scientists want to know if those sterile males still smell like normal wild flies. If not, the traps used to track the flies may need fixing too.

Screwworm was wiped out in the U.S. decades ago. Crews used the sterile fly method to do it. The fly came back this year. The first new U.S. case showed up in a three-week-old calf. This happened in Zavala County, Texas, on June 3, 2026. Maggots were found near the calf's belly button wound.

The USDA set up a 20 kilometer watch zone around that farm. Crews now release about 4 million sterile flies each week. Some drop from planes. Some come from ground boxes. Trappers watch the border for more flies. By late July 2026, the U.S. had 42 confirmed cases. Forty one of those cases are in Texas.

The outbreak also froze cattle trade with Mexico. The border has been shut to Mexican cattle since May 2025. The USDA now plans to reopen it a little at a time. That start date is August 24, 2026. Cattle will cross at one port in Douglas, Arizona. Only cattle from the safest parts of Mexico will be allowed in at first.

Agriculture Secretary Brooke Rollins called the long closure "tough but necessary." Texas Agriculture Commissioner Sid Miller welcomed the reopening. But he said the long wait hurt ranchers. "The prolonged closure has already taken a toll on producers, disrupted supply chains, and created uncertainty," Miller said. He also said the USDA spent "more than a year reacting instead of getting ahead of the problem."

South Texas ranchers now watch two things at once. One is how far the fly spreads. The other is how fast cattle trade opens back up at the border. The CSU smell study will not stop screwworm by itself. But a better trap bait could help crews find outbreaks faster. That could mean fewer sick animals down the road.