Researchers to test male-only genetically engineered screwworm in Panama as USDA ramps sterile-fly response after Texas detections

U.S.-funded researchers in Panama are preparing the first outdoor tests of a genetically engineered screwworm fly as the U.S. Department of Agriculture looks for ways to expand sterile-fly production after New World screwworm was confirmed in Texas in June. Reuters reported that the initial trial would use mesh cages at a Panama facility to see whether the modified flies can survive local heat and humidity before any broader release.

The timing matters because the pest is back in the United States for the first time in decades, and the existing response depends on a sterile-insect system that needs far more flies than current facilities can supply. Screwworm larvae infest open wounds in warm-blooded animals, including cattle and other livestock, feeding on living tissue and causing severe damage that can sometimes be fatal. Reuters reported that officials and experts have said the campaign may require hundreds of millions of flies a week, while USDA materials say the goal is to approach about 500 million sterile flies weekly.

The strain being tested, called NovoFly, is designed to produce only male screwworms for release. That matters because sterile insect programs work by rearing flies in large numbers, sterilizing the males and releasing them so they mate with wild females and collapse the population over time. Female production is largely wasted capacity in that system, so a male-only strain could make mass rearing much more efficient. Reuters quoted Scott Hutchins, USDA’s chief scientist and under secretary, saying, “It’s going to allow us to almost instantaneously double the number of sterile flies that we put in the fight. It’s going to give us a tremendous edge.”

Reuters reported that researchers were expecting approval from Panama’s biosecurity authorities for the cage-contained outdoor phase. If those tests succeed, a larger trial could follow at a nearby ranch in roughly nine to 12 weeks from mid-July, according to Reuters, citing USDA research geneticist Alex Arp. That next phase would involve releasing about 50,000 flies every few days and using fluorescent marking and trapping to measure survival. The uncertainty is basic but important: whether the engineered strain performs well outside controlled conditions. “We may get out in the field, and it may not fly very well,” entomologist Maxwell Scott told Reuters.

The regulatory track is moving in parallel. EPA public biopesticides materials show USDA has submitted both a standard Section 3 registration application for NovoFly and a Section 18 emergency or quarantine exemption request. EPA also listed a proposed registration comment period in June 2026. In Panama, however, Reuters said the outdoor cage trial was still awaiting or expecting local biosecurity approval, meaning the test had not yet begun.

USDA’s Animal and Plant Health Inspection Service, the agency leading the domestic response, confirmed the first U.S. New World screwworm detection in Texas on June 3, 2026, and a second detection on June 5. APHIS said it responded by setting 20-kilometer infested zones, imposing quarantines, expanding surveillance, deploying a strike team and diagnostic support, and intensifying sterile-fly releases. The agency said it began aerial releases on June 4 at 2 million sterile flies twice a week and was sending another 4 million per week for ground release.

USDA is also trying to rebuild production closer to home. The department broke ground on April 17 on a new sterile-fly production facility at Moore Air Base in Edinburg, Texas, intended to expand domestic capacity.

The U.S. eradicated New World screwworm in 1966 using the sterile insect technique, and a barrier program in Panama has long been used to slow the pest’s spread northward. The new Panama tests are an effort to update that same strategy for a moment when the insect has reappeared in Texas and the old response system is stretched.