The return of the screwworm
Screwworms were once endemic to the United States, but were exterminated in the 1960s by concerted efforts to exterminate their populations. This is done by aerial bombardment of sterile male flies, the most effective weapon against parasites. The mass release of mass rods dislodges fertile males and prevents them from mating with females, who generally mate only once.
With this method, called Sterile Insect Technique, flies were destroyed not only from the United States, but from all of Central America. They were declared extirpated from Panama in 2006.
Until recently, the screwworm population was protected by a biological barrier along the Darien Gap on the border between Panama and Colombia. The USDA partnered with Panamanian authorities to set up a sterile fly production facility in the gap to regularly release sterile flies and maintain the line. But in 2022, the barrier was breached, and the flies have been relentlessly buzzing north ever since.
In response, the US has expanded surveillance and trapping efforts in Texas. It is also building a $750 million sterile fly production facility in South Texas. The USDA says it is now distributing 100 million sterile insecticides per week in Mexico and along the U.S.-Mexico border to prevent further spread of the flies.
In a press release Wednesday night, the USDA said it would release sterile flies through ground release cameras in the area around the discovery. This is in addition to the 4 million flies already airlifted into the region this week.
“The United States has defeated this pest before, and we will do it again,” Dudley Hoskins, USDA’s Under Secretary for Marketing and Regulatory Programs, said in a press release.
This post was updated at 10:45 PM ET to reflect that the USDA confirmed the NW screwworm infestation.
