The Sterile Fly Defense
The United States is defending its $100 billion cattle industry from a flesh-eating parasite with a technology developed during the Kennedy administration: mass-producing sterile flies and dropping them from aircraft. The American Farm Bureau Federation wrote to USDA Secretary Brooke Rollins this week urging the agency to maintain this approach, because with over 600 active screwworm cases in Mexico and the northernmost detection now just 70 miles from the Texas border, nobody has a better plan.
New World screwworm fly larvae burrow into the flesh of living animals, causing damage that's often fatal. The parasite infests livestock, pets, wildlife, and in rare cases, people. The U.S. eradicated it in 1966 using sterile insect technique, but it never disappeared from Central and South America. Now it's surging north through Mexico, and the southern U.S. border has been closed to cattle imports since July 9, 2025.
Industrial-Scale Biological Warfare
The USDA currently produces 100 million sterile flies per week at a facility in Panama called COPEG, according to the agency's August announcement. Workers irradiate male screwworm flies to sterilize them, then release the insects over infested areas. When sterile males mate with wild females, no offspring result. Repeat this at sufficient scale and the population crashes.
It's the same method that eliminated screwworm from the United States sixty years ago. The difference is scale.
USDA completed a sterile fly distribution facility in South Texas to handle the current crisis. The agency is investing $21 million to help Mexico renovate an existing production facility. And it's constructing a new plant at Moore Air Force Base in Edinburg, Texas that will produce up to 300 million sterile flies per week. That's 15.6 billion flies per year, an industrial output that would have been unimaginable in 1966 but is now the minimum required to hold the line.
The ground operation in Mexico reveals the coordination required to make this work. USDA helped Mexico's agriculture authority SENASICA install 960 traps north of the current aerial dispersal zone. The agency assisted with hiring over 200 surge staff for fly trapping and animal movement controls. The Mexican government authorized 168 checkpoints for official inspections, preventative treatment, and wound care. At least 7,245 animals within Mexico received treatment.
Six Agencies, One Parasite
The federal response involves coordination across USDA, the Food and Drug Administration, the Environmental Protection Agency, the Department of Energy, Customs and Border Protection, and the Centers for Disease Control and Prevention. Each agency handles a different piece of the biosecurity puzzle.
FDA oversees animal drug development and approvals for prevention and treatment. EPA and DOE work on new technologies to combat the pest. CBP manages border protection. CDC handles the rare human cases, because screwworm can occasionally infest people.
This multi-agency structure reflects how agricultural biosecurity works in practice: threats don't respect bureaucratic boundaries, so response requires coordinating regulatory authorities that normally operate independently. The complexity is the point. A parasite that can cross from wildlife to livestock to humans needs monitoring systems that span veterinary medicine, environmental science, and public health.
The Buffer Zone Strategy
On August 19, USDA and SENASICA signed a collaborative Action Plan that formalized what was already happening: the United States investing heavily in Mexican infrastructure to maintain a buffer zone between active cases and the border. The $21 million for Mexico's facility renovation is part of this strategy. So is the technical assistance for trapping and checkpoints.
The logic is straightforward. Screwworm doesn't recognize international borders, and Mexico's geography makes it the natural barrier. If the parasite establishes itself in northern Mexico, the next stop is Texas. The two northernmost detections in Mexico occurred in Nuevo León in young cattle transported from Chiapas, demonstrating how animal movement spreads the infestation faster than the flies can migrate on their own.
USDA deployed over 113 screwworm-specific traps across high-risk areas of border states and examined more than 1,600 wild animals in high-risk Texas counties. As of October 17, no screwworm had been detected in any animals or traps in the United States. The border closure and surveillance system are working, for now.
What Happens When Proven Methods Aren't Enough
Farm Bureau President Zippy Duvall's letter urges USDA to keep the southern border closed to cattle imports until Mexico can control the pest. The phrasing is diplomatic, but the subtext is clear: ranchers along the border are watching case counts climb and the infestation creep north, and they want the proven defense maintained even if it means suspended trade.
USDA's response includes a $100 million investment in viable innovations to combat screwworm. That fund exists because the agency knows sterile insect technique, while effective, has limitations. It requires massive production facilities, constant aerial dispersal, and perfect execution across international borders. It worked when screwworm was eradicated from the U.S. in 1966 because the infestation was contained and the technology was new. Using it to defend against a surge from Mexico in 2026 means scaling 1960s biology to 21st-century threat levels.
The innovation fund is a hedge. USDA is coordinating with FDA on new drugs, with EPA and DOE on alternative technologies, while simultaneously building the Texas facility that will triple sterile fly production. The message is: we'll keep doing what works while hoping something better arrives in time.
The Vulnerability in the System
The current approach depends on Mexico maintaining control long enough for sterile fly saturation to collapse the wild population. But the northernmost case is now 70 miles from Texas, and Mexico is managing over 600 active infestations. The checkpoints, traps, and treatments are containment measures, not eradication. The U.S. is essentially building a biological moat and praying it holds.
Southern ports of entry remain closed to livestock imports, which protects U.S. herds but strangles cross-border trade. Ranchers can't import cattle. Mexican producers can't access U.S. markets. The economic pressure builds on both sides while the infestation persists.
The Farm Bureau's letter doesn't propose alternatives because there aren't obvious ones. Close the border, flood the zone with sterile flies, invest in Mexican infrastructure, hope for innovation. That's the playbook, and it's the same one used sixty years ago because it's the only one that's ever worked at scale.
The Texas facility in Edinburg will produce 300 million flies per week when complete, a capacity that seemed impossible in 1966 and barely sufficient now.