Does releasing sterile mosquitoes work?

What public programs have published, with the caveats left in.

Yes, when releases are designed well. Peer-reviewed US studies report up to 79% fewer adult mosquitoes in the first release phase of a Florida program using the same irradiation method SMF uses, and 93% to 95.5% fewer females with a related method. The strongest results come from well-buffered areas where few wild females fly in, which is how we plan every program.

Lee County MCD, Morreale et al., PLOS NTD, 2025. Harris County, Lozano et al., PLOS NTD, 2022. Fresno, Crawford et al., Nature Biotechnology, 2020.

How to read this page

These are other organizations' results, shown as evidence for the method. They are not SMF's results.

Irradiation SIT (same method as SMF) means males were sterilized with radiation. Ours are sterilized with X-rays.
Wolbachia (related method) means males carried a bacterium that stops eggs from hatching. The outcome is similar; the method and regulation are different.
Peer-reviewed studies were checked by independent scientists before publication. District-reported and company-reported figures were not, and we label them that way.

Same method as SMF

Irradiation SIT (same method as SMF)

Lee County, Florida (Captiva Island)

Status: Peer-reviewed
Years: June 2020 to September 2022
Species: Aedes aegypti (yellow fever mosquito)

Key result

Up to 79% fewer wild adult mosquitoes and 59% fewer eggs in the first release phase (about 63 ha, 2020 to 2021), compared with an untreated island (northwest Sanibel).¹

Scale

More than 24.1 million X-ray sterilized males, released over up to 142 hectares (about 350 acres).¹ Lee County's quality-control threshold for females was 0.2% or less.¹

What to keep in mind

The 79% and 59% results come from Phase 1, the first release area of about 63 hectares, June 2020 to May 2021.¹
When the release area was expanded in Phases 2 and 3, the main analysis found no statistically detectable effect. The authors point to mated wild females flying in from untreated areas.¹ The lesson for any program, including ours: release design and buffer zones matter, and larger, contiguous areas hold results better.
The drop in egg hatch was not statistically significant, so we don't claim it.¹
Hurricane Ian ended the island program in 2022. The district moved releases to Fort Myers in 2024 and has not yet published numbers from there.²

Citation

Morreale R, Carvalho DO, Stenhouse S, Bajonero J, Pereira R, Hahn DA, Lloyd A, Hoel DF. "Suppression of Aedes aegypti by the sterile insect technique on Captiva Island, Florida, USA from 2020 to 2022." PLOS Neglected Tropical Diseases 19(7): e0013256, 2025. doi:10.1371/journal.pntd.0013256 · https://pmc.ncbi.nlm.nih.gov/articles/PMC12310038/

1. Morreale et al., PLOS NTD, 2025. 2. Morreale et al., "Overview of the sterile insect technique for Aedes aegypti in Lee County, Florida, USA," Infectious Diseases of Poverty 14: 37, 2025. doi:10.1186/s40249-025-01307-7. Hectare to acre conversion is ours.

Irradiation SIT (same method as SMF)

West Valley, California

Status: Peer-reviewed
Years: April to November 2024
Species: Aedes aegypti (yellow fever mosquito)

Key result

44% fewer female mosquitoes per trap-night with sterile males alone, and 65% fewer combined with In2Care larvicide stations. Resident service requests about Aedes mosquitoes fell 44%, from 656 to 367. In the program's sterility checks, more than 99.6% of eggs from females that mated with sterile males did not hatch.¹

Scale

106,608 sterile males released at 25 hotspots across the district.¹

What to keep in mind

Results compare 2024 with the year before releases at the same sites, not with an untreated control area. It is a before/after comparison.
Males were released every two weeks, at hotspots, over one season, with far fewer males in total than Lee County.
The 65% result came from combining sterile males with another tool: In2Care stations, which spread larvicide. There was no stations-only comparison. Public programs often combine tools.
Service requests measure what residents noticed, which is useful but less precise than trap counts.

Citation

Birhanie SK, et al. "Reduction in Aedes aegypti Population After a Year-Long Application of Targeted Sterile Insect Releases in the West Valley Region of Southern California." Insects 16: 81, 2025. doi:10.3390/insects16010081

1. Birhanie et al., Insects, 2025.

Related method (Wolbachia)

Harris County, Texas (Houston area)

Status: Peer-reviewed, independent evaluation by the CDC and Harris County Public Health, with UTMB; releases by MosquitoMate
Years: June to August 2019
Species: Aedes aegypti (yellow fever mosquito)

Key result

93% fewer wild female mosquitoes after six weeks of continual releases, and about 94% fewer week after week through the rest of the trial.¹

Scale

An 18.6 hectare (about 46 acre) treatment area compared with a 29.6 hectare untreated area, with traps at 55 homes.¹

What to keep in mind

Wolbachia males, not irradiated males. It shows that sterile-male releases work in Texas conditions; it doesn't describe SMF's exact method.
One summer, one neighborhood. The authors recommend larger randomized designs for more statistical power.¹
The authors noted a possible increase in Asian tiger mosquitoes, a different species, in the treated area, and treat it with caution.¹

Citation

Lozano S, Pritts K, Duguma D, Fredregill C, Connelly R. "Independent evaluation of Wolbachia infected male mosquito releases for control of Aedes aegypti in Harris County, Texas, using a Bayesian abundance estimator." PLOS Neglected Tropical Diseases 16(11): e0010907, 2022. doi:10.1371/journal.pntd.0010907 · https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0010907 (public domain)

1. Lozano et al., PLOS NTD, 2022.

Fresno, California

Status: Peer-reviewed
Years: 2018 season
Species: Aedes aegypti (yellow fever mosquito)

Key result

95.5% fewer female mosquitoes at peak season, and up to 99% in the most isolated neighborhood.¹

Scale

14.4 million males released over 293 hectares in three neighborhoods.¹

What to keep in mind

Wolbachia males, with automated rearing and sorting by a large technology company working with the local district.
The best result came in the most isolated neighborhood, the same lesson as Lee County: fewer wild females flying in means stronger results.
A later published critique questioned parts of the analysis, including the effect of mosquitoes moving in.²

Citation

Crawford JE, et al. "Efficient production of male Wolbachia-infected Aedes aegypti mosquitoes enables large-scale suppression of wild populations." Nature Biotechnology 38: 482-492, 2020. doi:10.1038/s41587-020-0471-x

1. Crawford et al., Nature Biotechnology, 2020. 2. Bouyer, Maiga and Vreysen, Nature Biotechnology, 2022.

South Miami, Florida

Status: Peer-reviewed study; the 78% figure is company-reported
Years: About 6 months
Species: Aedes aegypti (yellow fever mosquito)

Key result

Significant reductions in adult Aedes aegypti.¹ MosquitoMate, the company that ran the releases, reported a 78% reduction, as cited in Lozano et al. 2022 (company-reported figure).²

Scale

A release area of about 170 acres.¹

What to keep in mind

Wolbachia males, not irradiated.
The original paper's abstract gives no single percentage. The 78% is MosquitoMate's own figure, repeated in a later peer-reviewed paper; local news reported 75%.² ³

Citation

Mains JW, Kelly PH, Dobson KL, Petrie WD, Dobson SL. "Localized Control of Aedes aegypti in Miami, FL, via Inundative Releases of Wolbachia-Infected Male Mosquitoes." Journal of Medical Entomology 56: 1296-1303, 2019. doi:10.1093/jme/tjz051

1. Mains et al., J Med Entomol, 2019. 2. MosquitoMate, as cited in Lozano et al., PLOS NTD, 2022, https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0010907 3. WLRN, June 10, 2019.

Sacramento-Yolo, California

Status: District-reported, no published dataset
Years: July to November 2025 pilot; expanded July 2026
Species: Aedes aegypti (yellow fever mosquito)

Key result

The district reported about 40% fewer mosquitoes in its first pilot area, and expanded the program the following year.¹ ²

Scale

About 400,000 males in the 2025 pilot. The 2026 expansion covers about 120 acres with about 2.3 million males over 16 weeks.³ ⁴

What to keep in mind

District staff shared the figure in city council briefings and news coverage. No trap data has been published yet, so treat it as an early report.
Sources disagree on the size of the 2025 pilot area (about 25 acres or 100 acres), possibly release zone versus evaluation zone.

Sources

Sacramento-Yolo Mosquito and Vector Control District briefings to the Woodland City Council (May 19, 2026) and Citrus Heights City Council (May 28, 2026), via Citizen Portal. District SIT bulletin: https://www.fightthebite.net/sit-bulletin · CBS Sacramento, July 8, 2025: https://www.cbsnews.com/sacramento/news/sterile-mosquitoes-released-sacramento-south-natomas-disease/

1. Citizen Portal, Woodland council briefing, May 19, 2026. 2. Citizen Portal, Citrus Heights council briefing, May 28, 2026. 3. CBS Sacramento, July 8, 2025; CapRadio, September 2, 2025. 4. Univision Sacramento, 2026.

From our technology partner

Irradiation SIT, on Senecio's AI sorting and release technology, which SMF also uses

Senecio, Israel

Status: Company-reported, not peer-reviewed
Years: 2023 pilot; municipal programs from 2024
Species: Aedes albopictus (Asian tiger mosquito)

Key result

Senecio reports declines of up to about 90% over three seasons, and "80% within a few weeks."¹ Managers at two kibbutzim wrote that within about two months they "hardly" received mosquito complaints.²

Scale

Programs in 7 municipalities and communities in the 2024 season, most delivered with Rentokil Israel (Rentokil Initial), plus releases at hundreds of locations (company-reported).³

What to keep in mind

These are our partner's own figures. No controlled trial or trap dataset has been published, and the "80%" figure has no stated location or year.
We include them because they show the technology working at municipal scale, not as proof of a specific result.

Sources

Senecio Robotics, https://www.senecio-robotics.com/ and https://heb.senecio-robotics.com/summer2026 · Municipal reference letters, Kibbutz Eyal and Nir Eliyahu, September 2024 (Senecio website PDF) · Senecio and Rentokil, 2024 season announcement: https://www.senecio-robotics.com/post/senecio-and-rentokil-partner-to-serve-7-municipalities-in-2024-mosquito-season

1. Senecio Robotics website, company-reported. 2. Reference letters, September 1 and 7, 2024. 3. Senecio Robotics, 2024 announcement and FAQ.

What the evidence adds up to

Read together, these programs point the same way, and they also show what makes the difference.

The method works on the yellow fever mosquito in the US. Two independent irradiation programs and four Wolbachia programs (three peer-reviewed) report reductions.
Design decides the result. The strongest numbers come from isolated or well-buffered areas. Where wild females flew in from untreated land, results faded.
Combining tools helps. The best West Valley result came from sterile males plus In2Care larvicide stations. Removing standing water still matters.
Measurement matters. Every credible program counted mosquitoes before and during releases.

A note on species: most US results above are for Aedes aegypti (yellow fever mosquito). SMF releases both Aedes aegypti and Aedes albopictus (Asian tiger mosquito). Senecio's reported programs in Israel target Aedes albopictus.

FAQ

Lee County: Morreale et al., PLOS NTD, 2025. Harris County: Lozano et al., PLOS NTD, 2022.

Do sterile mosquito releases actually work?

Published US programs say yes, for the species released. Lee County, Florida, reported up to 79% fewer adult mosquitoes in its first release phase, using the same irradiation method as SMF. Results depend on release design and how many wild females fly in from untreated areas.

Have sterile mosquitoes been released in Texas?

Yes. In 2019, Harris County Public Health and the CDC evaluated releases of Wolbachia-carrying males (a related method) near Houston and found 93% fewer wild females after six weeks.

Why didn't Lee County's results last when the program expanded?

The peer-reviewed analysis found no detectable effect in the expanded areas, likely because mated females flew in from untreated neighborhoods. It's the main reason we plan release buffers and favor larger, contiguous areas.

Are these SMF's results?

No. They are results from public programs and our technology partner, shown as evidence for the method. SMF client results are published here only with the client's permission.

What's the difference between irradiation and Wolbachia results?

Both release males whose matings produce no offspring. Irradiated males are sterilized with radiation. Ours are sterilized with X-rays. Wolbachia males carry a bacterium. We label every result by method.

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