The sterile insect technique, explained

Pests multiply because every female lays eggs that hatch. Interrupt that, and the next generation never arrives.

Female Aedes mosquitoes mate only once and store that sperm for life. So if a sterile male gets to her first, she lays eggs that won't develop. Release enough sterile males, week after week, and most wild females end up with one of them. Each generation is smaller than the last. No chemicals are needed, and the only insects affected are the species released.

SIT isn't new. It is one of the most studied biological control methods in the world.

Screwworm flies. SIT first proved itself against the screwworm, a fly whose larvae feed on the living flesh of cattle and other animals. Sterile fly releases became a long-running tool for protecting livestock.¹

Mediterranean fruit flies. Agriculture programs release sterile medflies to protect fruit crops and orchards.¹

Mosquitoes. Mosquitoes are harder. Males and females must be sorted precisely, and the males must stay strong enough to compete after sterilization. Public mosquito control districts in Florida and California now run programs with irradiated sterile males, and publish the results.² The IAEA's phased, step-by-step approach to testing and scaling guided programs such as Lee County's.³

It's the cleanest version of the idea. Nothing is added to the mosquito. The only thing the male loses is the ability to father offspring.

• Nothing added. No engineered genes and no bacteria go into the environment.
• Nothing to spread. A sterile male leaves no offspring, so there is nothing that carries on after he dies, a few days after release.¹
• The longest track record. Radiation is how SIT has worked since the beginning, for flies and now for mosquitoes.²
• Plain for neighbors. The Lee County district found that comparing the process to a medical X-ray reassured residents, and pushback was "virtually nonexistent."³

1. Field life expectancy about 2.46 days. Carvalho et al., Parasites & Vectors, 2022. 2. IAEA, https://www.iaea.org/topics/sterile-insect-technique 3. Morreale et al., Infectious Diseases of Poverty, 2025.

Mosquitoes find mates by species. A male of one species doesn't mate with another, or with bees, butterflies or anything else.

That's what makes SIT so precise, and also its limit. The CDC puts it plainly: SIT reduces only the type of mosquito that was sterilized and released, not all mosquitoes.¹

We release males of the species that bite in yards by day and at dusk: the Asian tiger mosquito and the yellow fever mosquito (Aedes). The mosquitoes that bite at night are a different species and aren't affected by our releases. If night biting is a big problem on your property, we'll tell you, and we'll talk through what else helps.

1. CDC, "Irradiated mosquitoes," cdc.gov, May 14, 2024.

Three lessons shape how we design every program.

• Release design matters. In Lee County, Florida, releases brought up to 79% fewer adults and 59% fewer eggs in the first release phase (about 63 ha, 2020 to 2021), compared with an untreated island. When the area expanded in later phases, the main analysis found no detectable effect, as wild females flew in from untreated neighborhoods.¹ That's why we plan buffers and favor whole-community programs.
• The best evidence is controlled. The programs worth citing ran traps before and during releases, and compared against untreated areas.
• Scale is the hard part. Raising and sorting millions of healthy males used to take rooms full of people. AI sorting, from our technology partner Senecio, is what makes SIT practical for private properties.

1. Lee County Mosquito Control District, Captiva Island, FL. Morreale et al., PLOS Neglected Tropical Diseases, 2025.