The Screwworm Problem Will Get Worse Before It Can Get Better

This time a year ago, experts were already predicting the return of flesh-eating screwworms to the United States: a matter of not if but when, Wayne Cockrell, a Texas rancher, lamented to me at the time. Screwworms had been eradicated from the U.S. to Panama and then were cordoned off through the continual release of almost 20 million sterilized screwworms every week over the narrow Isthmus of Panama. But screwworms, which grow into flies as adults, had jumped the cordon and infested a large swatch of Mexico by last year. This month, they indeed reached Texas.The math of the crisis then and now is brutally simple: The U.S. Department of Agriculture’s screwworm program cannot produce enough sterile adults to get the parasites under control. A factory in Panama has already quintupled its weekly production to its physical max, just more than 100 million, but more, many more, flies are needed to re-eradicate the screwworm: 500 million.Two new factories are under construction, but both were delayed, according to reporting in Politico, by the Trump administration’s aggressive reviews of government spending last year. The first, in Mexico, will be fully online only this fall and the second, a much larger one in Texas, in the fall of 2028. “To win this war, it’s all about the number of sterile flies,” Cockrell, who is also second vice president of the Texas and Southwestern Cattle Raisers Association, reiterated to me recently.In the meantime, the screwworms will keep percolating through the country, and ranchers will keep finding the grisly, telltale wounds in their livestock. The best that ranchers can do until more sterile flies arrive is “hold the line, weather the storm,” Jason Sawyer, the chief science officer of the East Foundation, an agricultural-research organization that manages six ranches in Texas, told me. Optimistically, he expects the re-eradication of screwworms in the U.S. to take three years. Realistically, he thinks it’ll take five years.The parasites po