Researchers launch sterile fly drop to combat NWS

By Breyana Segura - Chief Staff Writer | June 17, 2026

Two active cases confirmed in La Salle County

Federal agriculture officials and local authorities are intensifying surveillance and elimination efforts across South Texas as the New World Screwworm (NWS) continues a rapid migratory spread northward from Mexico, threatening both the livestock industry and the upcoming regional hunting season.

In response to the mounting threat, agriculture authorities released 80,000 sterile flies earlier this month in Zavala County after the confirmation of the NWS.

The time-tested biological control method relies on mass-releasing sterile male flies into the wild to mate with wild females.

Due to female screwworm flies only mating a single time during their lifespan, mating with a sterile male ensures she will produce no offspring, causing a localized population collapse.

The situation remains highly fluid as the infestation continues in south and central Texas and as the NWS continues its rapid spread into Texas from Mexico, federal officials have intensified surveillance and elimination efforts along the border.

On Monday, La Salle County Judge Leodoro Martinez’ office confirmed two active, verified cases of NWS within the county, noting that both detections were located on ranches outside of the municipal city limits.

To combat the outbreak with real-time data, the U.S. Department of Agriculture (USDA), launched an up-to-date monitoring dashboard to provide a snapshot of confirmed NWS detections.

As of Monday, federal data shows 12 confirmed animal cases within the U.S. Of those detections, 11 are concentrated in Texas, while the remaining case is in a New Mexico county adjacent to the Texas border.

A breakdown of the livestock data shows that since June 3, inspectors have confirmed NWS infections in eight cattle, two goats, one sheep, and one dog.

Furthermore, of the 11 Texas cases, one is now inactive.

According to the USDA, an inactive classification refers to situations where mitigation activities are no longer required. Either this occurs because the infected animal has fully recovered with wounds and finished treatment or treatment was not performed or appropriate measures taken prevented the spread of NWS.

The state’s most recent detection, discovered on June 12 in Sutton County, is now inactive.

The central testing hub for all suspected NWS samples is the newly opened Knipling-Bushland U.S. Livestock Insects Research Laboratory in Kerrville.

The facility, named after Dr. Edward Knipling and Raymond Bushland, USDA researchers who developed the sterile insect technique that helped eradicate screwworm from the U.S., Mexico, and Central America in the 1960s, opened in May.

Current researchers at the Kerrville facility developed a new strain of sterile fly known as the Novo fly. Researchers expect the Novo strain to significantly expand elimination efforts.

In an effort to support the containment strategy, the USDA is collaborating with the U.S. Army Corps of Engineers to build a permanent sterile fly production facility at Moore Air Base in Edinburg.

Officials say the facility will be capable of producing up to 300 million sterile flies per week.

Despite the rapid mobilization of federal science resources, anxiety throughout the South Texas economy is growing.

Local ranchers remain on high alert for livestock wounds, and area residents expressed fears that an unchecked screwworm outbreak could severely impact wildlife populations and disrupt the upcoming hunting season, which serves as a vital economic driver for the region.