Topeka, Kansas – The US government is gearing up to breed billions of flies, which will be released from planes in Mexico and southern Texas to combat meat-eating maggots.

This may sound like a horror movie plot, part of the government’s strategy to safeguard the US from pests that threaten the beef industry, wildlife, and even household pets. This innovative method has proven effective in the past.

“It’s an excellent technique,” remarks Edwin Burgess, an assistant professor at the University of Florida, who studies animal parasites, particularly in livestock. “It’s the best method we have for translating science into solving significant problems.”

The targeted pests are the meat-consuming larvae of the New World Screwworm Fly. The USDA is set to ramp up the breeding and distribution of adult male flies that will mate with wild females, resulting in eggs that will not hatch. Consequently, the larval population will decline over time.

This method is more effective and environmentally friendly than conventional pest control, which was used by the US and other countries north of Panama to eradicate these pests decades ago. Sterilized flies from Panama were effective for years, yet infestations resurfaced in southern Mexico late last year.

The USDA anticipates that a new Screwworm Fly Factory will begin operations in southern Mexico by July 2026. Additionally, a fly distribution center will be established in southern Texas by the end of this year, facilitating the import and distribution of flies from Panama as required.

Fried Live Meat

Most fly larvae consume dead flesh, feeding on decomposing matter from the New World screwworm as well as its counterparts from Asia and Africa, posing a significant threat to the American beef industry. Females lay eggs in wounds, which can sometimes expose the underlying tissue.

“A 1,000-pound cow could perish within two weeks,” stated Michael Bailey, the elected president of the American Veterinary Association.

Veterinarians have effective treatments for infested animals; however, an invasion can still cause significant discomfort and pain for affected animals.

Don Hineman, a retired rancher from Western Kansas, recalls an infected cow from his youth on the family farm.

“It had a terrible smell,” he recounted. “Like rotten meat.”

Utilizing Fly Biology Against Them

The New World Screwworm Fly is a tropical species that historically could not survive winters in the Midwest and Great Plains. However, from 1962 to 1975, the US and Mexico raised and released over 94 billion sterile flies, according to the USDA.

The numbers must be large enough so that wild females have no option but to mate with sterile males.

A unique biological characteristic gives fly fighters an edge: females mate only once during their adult life over a short period.

Reasons for Increased Fly Breeding

Concerns have been raised about the potential northward movement of flies. The southern border has been closed to imports of live cattle, horses, and bison, which won’t fully reopen until at least mid-September.

However, female flies can inflict wounds on warm-blooded animals, including humans.

Decades ago, the US operated fly factories in Florida and Texas, which were shut down after the pests were eradicated.

Panama’s fly factory can produce up to 117 million flies per week, but the USDA aims to boost production to at least 400 million per week. It plans to invest $8.5 million in a Texas facility and $21 million to transform it into a breeding site for screwworm flies and fruit flies in southern Mexico.

Methods for Cultivating Millions of Flies

Growing large populations of flies is relatively simple, according to Cassandra Olds, an assistant professor of entomology at Kansas State University.

She notes, however, that “you need to provide females with the necessary cues to lay their eggs, and the larvae must have sufficient nutrients.”

Previous USDA studies indicate that larvae were once fed horse meat and honey before transitioning to a blend of dried eggs and honey or molasses. The Panama facility eventually utilized a mixture of egg powder, red blood cells, and cow plasma.

In nature, larvae, akin to the pupal stage of butterflies, fall from their hosts to the ground, burrowing just below the surface to grow inside a protective casing resembling a dark brown tic-tac mint. In the Panama factory, workers place them into sawdust trays.

Security measures are crucial. According to Sonja Swiger, an entomologist at Texas A&M University’s Extension Services, breeding facilities need to prevent fertile adults from the breeding stock.

Aerial Fly Release

Dropping flies from aircraft presents certain risks. Recently, a plane releasing sterile flies crashed near the Mexican border, resulting in three fatalities.

Historically, during test runs in the 1950s, scientists placed flies in paper cups, which were then dropped from the planes using a specialized chute. These cups were loaded into boxes on a machine called the “whiz packer.”

The current method closely resembles this. Small aircraft equipped with wooden trays release the flies.

Burgess is recognized for developing the breeding and distribution of sterile flies in the 1950s and 60s, labeling it one of the USDA’s “greatest accomplishments.”

Some farmers now contend that new factories shouldn’t be closed after another successful eradication.

“What we perceive as full control — and declare victory — can always reemerge,” cautioned Burgess.