Fighting the larvae plague Curious but effective: USA wants to drop billions of flies over Mexico

Carnivorous larvae from Mexico are threatening the USA with massive damage to agriculture. Now the government has a plan: billions of flies are to be dropped from airplanes over the neighboring country.

The USA is facing a threat in the form of a fly plague: the flesh-eating larvae of the so-called New World screwworm fly could cause major damage to the country's agriculture and wildlife. As the plague is moving ever closer to the US border from Mexico, the government under President Donald Trump has now come up with a bizarre plan: Billions of sterile male flies of this species are to be bred and dropped from airplanes over Mexico and South Texas.

What sounds like a scenario from a horror movie is actually a proven and effective method. "It's an exceptionally good technology," Edwin Burgess, assistant professor at the University of Florida, told the Guardian newspaper."When it comes to finding solutions to big problems, it's one of the greatest scientific achievements."

How the "sterile insect technique" works

We are talking about the so-called "sterile insect technique", which the US Department of Agriculture (USDA) wants to use to control the pests. The new world screwworm fly is to be bred en masse and then released. Beforehand, the male insects are sterilized by irradiation. In the wild, they then mate with the females, whose eggs remain unfertilized and do not hatch. This results in fewer larvae and the species gradually dies out.

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As unusual as the measure sounds, it is intended to protect US agriculture. "The only way to protect the American cattle herd from the devastating threat of the New World screwworm fly is to ensure an adequate supply of sterile flies to keep this pest away from our border," Buck Wehrbein, President of the National Cattlemen's Beef Association, told the political magazine "Axios"

"Devastating pest"

The New World screwworm fly poses a threat to humans and animals through its larvae, which can penetrate open wounds in living creatures and become life-threatening for them. Spread en masse, they can endanger entire animal populations. The fly is a "devastating pest that causes serious and often fatal damage to livestock, wildlife, pets and, in rare cases, humans", explains the USDA on its website in June.

The insect is native to tropical regions, so it has actually always been a seasonal pest in the USA and Mexico. Nevertheless, both countries felt compelled to take extensive measures in the 1960s. As reported by the Guardian, more than 94 billion sterile flies were bred and released between 1962 and 1975 as part of a large-scale sterilization campaign to eradicate the pest.

Fly breeding facilities

After the fly reappeared in southern Mexico at the end of 2024, the authorities are now relying on the tried-and-tested method. US and Mexican institutions want to work together to achieve this. "Mexico will begin renovating its sterile fruit fly facility in Metapa this week, which is expected to be completed by July 2026," says the USDA. This facility is expected to produce 60 to 100 million sterile male flies per week. The goal is to increase capacity to 400 to 500 million flies.

In addition, a further plant is to be built in the US state of Texas by the end of this year. According to the authority, these could "increase domestic production of sterile flies by up to 300 million per week and supplement existing production in Panama and Mexico". Because containing the plague and eradicating the fly is something the government under Donald Trump is determined to do: "The United States has defeated the New World screwworm fly before, and we will do it again," said Secretary of Agriculture Brooke L. Rollins in a statement.