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A Billion Flies to the Rescue! Scientists Fight a Pest With a Sneaky Trick
Quick Summary
A harmful insect called the New World screwworm has returned to parts of the United States for the first time in decades. It can hurt farm animals and wildlife. But scientists have a brilliant plan to stop it — and it involves releasing over a billion specially raised flies!
What Happened?
Scientists once completely wiped out a troublesome fly from the United States. Now that fly has come back, and researchers are using the same clever trick that worked before.
The insect is called the New World screwworm. It is a type of fly. Its larvae, which are tiny worm-like creatures, burrow into the wounds of living animals. That makes it dangerous for cows, horses, dogs, deer, and other warm-blooded creatures. Think of it like a tiny unwanted passenger that hides inside an animal’s injury and grows there.
For more than 60 years, the screwworm was considered gone from the U.S. Then, in 2023, it broke through a barrier in Central America and began moving north — through Panama, Costa Rica, Guatemala, Mexico, and finally into Texas. In June 2026, the U.S. Department of Agriculture, called the USDA, confirmed the first cases on U.S. soil.
So far, fewer than 50 cases have been confirmed in the United States. The risk to people is very low, and the USDA says the food supply is completely safe.
Now here comes the clever part. The USDA is fighting back using a method called the Sterile Insect Technique. Scientists raise millions of screwworm flies, but they treat the flies with low-level radiation so the flies cannot have babies. Then, aircraft fly over affected areas and release these sterile flies by the millions.
When sterile flies mate with wild screwworm flies in nature, no eggs are produced. Over time, the wild population shrinks and shrinks — until there are none left. It is like hitting the delete button on an entire pest species.
In early September, the USDA celebrated a major milestone: one billion sterile flies had been released into Texas. The agency plans to ramp up production to about 500 million sterile flies every single week. That is about the same number used to erase the screwworm the first time, back in the 1960s and 1970s.
Scientists at UC San Diego are also building new tracking tools to predict exactly where the pest might spread next — like a weather map, but for bugs.
Why Does It Matter?
The screwworm outbreak is a reminder that nature is always changing. A pest that was defeated once can come back if the conditions are right.
But it is also a reminder of something wonderful: science has already solved this problem before! The sterile insect method is like having a secret weapon already in hand. Scientists, farmers, veterinarians, and government agencies are all working together as one giant team.
The U.S. eradicated the screwworm once. Researchers and officials are confident it can be done again.
Big Words
- Screwworm — a type of fly whose larvae burrow into the wounds of living warm-blooded animals
- Sterile — unable to have babies or reproduce
- Sterile Insect Technique — a clever scientific method of releasing infertile insects to reduce a pest population without using harmful chemicals
- Eradicate — to completely get rid of something so it no longer exists in an area
- Larvae — the young, worm-like form of an insect just after it hatches from an egg
Fun Fact
The screwworm gets its unusual name from the shape of its larvae — the tiny creatures twist like a corkscrew as they burrow, which reminded early scientists of an old-fashioned screw!
Think About It
The sterile insect technique works without using any chemical pesticides. Can you think of other creative, nature-friendly ways scientists might stop harmful insects from spreading?
Sources
- USDA APHIS — USDA Confirms Presence of New World Screwworm in the United States
- USDA Screwworm.gov — New World Screwworm Response
- CNN — A billion flies are now in the screwworm fight. Will there be enough?
- ScienceDaily — The U.S. Eradicated this flesh-eating parasite. Now it’s back
- CDC — New World Screwworm Outbreak Situation Summary