The U.S. government is embarking on an ambitious plan to breed billions of flies and release them over Mexico and southern Texas in a bid to combat a dangerous flesh-eating maggot. This initiative, which may sound like a plot from a horror film, is actually a strategic move to protect the U.S. beef industry, wildlife, and household pets from a potentially devastating pest.
The targeted pest is the New World Screwworm fly, whose flesh-eating larvae pose a significant threat. The U.S. Department of Agriculture (USDA) is planning to breed and release sterilized adult male flies, which will mate with females but produce no offspring, ultimately leading to a decline in the pest population. This method is considered more environmentally friendly and effective than traditional pesticide use and has been successfully implemented in the past.
The Science Behind the Strategy
This innovative approach is not new. According to Edwin Burgess, an assistant professor at the University of Florida, the technique is “an exceptionally good technology” and a prime example of applying science to solve large-scale problems. The USDA’s plan involves ramping up the breeding of these sterilized flies, a method that has proven successful in eradicating the pest from the U.S. and other regions north of Panama decades ago.
The USDA intends to establish a screwworm fly factory in southern Mexico by July 2026 and a distribution center in southern Texas by the end of this year. These facilities will ensure a steady supply of sterile flies, crucial for maintaining control over the pest population.
Understanding the Threat
Unlike most fly larvae that feed on dead flesh, the New World screwworm fly targets live tissue, making it a formidable threat to livestock. Female flies lay their eggs in wounds or exposed tissue, and the larvae can quickly incapacitate or even kill affected animals. Michael Bailey, president-elect of the American Veterinary Medicine Association, warns that a “thousand-pound bovine can be dead from this in two weeks.”
Veterinarians have treatments available for infested animals, but the process is unpleasant and can cause significant pain to the affected livestock. Don Hineman, a retired Kansas rancher, recalls the unpleasant experience of dealing with infected cattle during his youth, describing the smell as “nasty” and reminiscent of “rotting meat.”
Leveraging Biological Traits
The New World screwworm fly’s biology provides a key advantage in combating the pest. Females mate only once in their lifetime, which means that releasing a large number of sterile males can effectively reduce the population. From 1962 to 1975, the U.S. and Mexico released over 94 billion sterile flies to eradicate the pest, demonstrating the method’s efficacy.
Alarmed by the pest’s northward migration, the U.S. temporarily closed its southern border to imports of live cattle, horses, and bison in May, a measure expected to remain in place until at least mid-September. The USDA is also planning significant investments to increase fly production capabilities, aiming to breed at least 400 million flies weekly.
Challenges in Fly Breeding
Raising a large colony of flies presents its own set of challenges. According to Cassandra Olds, an assistant professor of entomology at Kansas State University, it’s crucial to provide the right conditions for female flies to lay eggs and ensure the larvae have sufficient nutrients. Traditionally, fly factories used horse meat and honey, but more recent methods have included egg powder and cattle blood products.
Security is also a concern, as noted by Sonja Swiger, an entomologist with Texas A&M University. Breeding facilities must prevent fertile adults from escaping, which requires stringent containment measures.
Deployment and Future Implications
Dropping flies from airplanes is not without risks. A recent accident involving a plane releasing sterile flies near Mexico’s border with Guatemala resulted in fatalities, highlighting the dangers involved. Historically, the USDA used paper cups and later crates to release flies, a method that remains largely unchanged today.
Edwin Burgess emphasizes the importance of maintaining fly factories even after successful eradication efforts. “Something we think we have complete control over—and we have declared a triumph and victory over—can always rear its ugly head again,” he cautions.
The USDA’s current efforts represent a proactive approach to pest management, aiming to safeguard the agricultural industry and prevent future outbreaks. As the program progresses, it will be crucial to monitor its impact and adapt strategies as necessary to ensure long-term success.
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