In early June, a South Texas rancher detected the first New World screwworm fly case in U.S. cattle in decades. Since then, 46 additional cases have emerged across 18 counties in two states. The Agriculture Department has spent over $1 billion to combat the reappearance.

A primary monitoring tool, sticky flytraps, has caught zero wild screwworm flies despite deploying 128 screwworm-specific traps and 8,000 exotic fruit fly traps. This absence complicates efforts to determine the outbreak's origin. To suppress wild populations, the Department releases sterile male flies; however, the breeding process also releases sterile females.

In November 2024, detections spread to Mexico, prompting the U.S. Department to deploy enhanced traps along the border. As of August 11, over 80,000 common flies like green bottle flies were captured for identification, yet not a single wild screwworm fly was found. Officials suggest this indicates only a very small number of fertile flies remain, rather than a large local population.

Nonetheless, entomologists warn that because a single female lays hundreds of eggs, undetected infestations could rapidly escalate. Live cattle imports from Mexico remain suspended, though limited entry into Arizona is set to resume. Localized quarantine zones are active wherever cases are detected.

While traps have yet to capture target pests, they provide data on fly habitats and modeling accuracy.