Toulouse released sterile mosquitoes in a cemetery. 200,000 a week is the plan.

On 26 May 2026, in the Terre-Cabade cemetery in Toulouse, a field team opened a set of small containers and released several thousand sterile male mosquitoes. The programme plans to release 200,000 a week through the season. Every one was male and sterile. Each one had a single job: to find a wild female, mate with her, and leave her laying eggs that never hatch.

This is the most concrete European deployment we have seen, outside a controlled trial, of the sterile insect technique (SIT) against Aedes albopictus, the tiger mosquito that carries dengue, chikungunya and Zika. The cemetery is only the launch pad. Les Echos reports that the operators intend to scale the release across the wider treatment area. They expect the zone to be largely free of the mosquito within two years.

How a sterile male reduces the population

The logic is old and simple. Only the female bites, and she is the one the sterile males are for. Release enough of them to outnumber the wild males in a neighbourhood, and a wild female is likely to mate with a sterile one instead. She lays her eggs, and none of them hatch. Repeat it season after season, with the sterile males always outnumbering the wild ones, and the next generation keeps shrinking until the local population declines.

Producing those males is the hard part. In a dedicated facility, the males are given a measured dose of ionising radiation, most often X-rays, sometimes gamma, calibrated to damage the sperm without otherwise harming the insect. The survivors are sorted, packed, and released by ground teams or by drone. No insecticide touches the ground. Nothing is genetically modified. The effect also ends on its own: the released males are sterile, and the eggs the females lay are empty. The same principle has controlled the Mediterranean fruit fly and other agricultural pests for decades, and it is now applied to the mosquito on your ankle.

One scientist at France's IRD (Institut de Recherche pour le Développement) in Montpellier, which helped launch Terratis, called the wider French effort "iPhone 1.0 stage". The idea is proven, and the mass production is still being built.

The numbers, in the order that matters

Here is what Toulouse has actually done, and what it has so far only promised.

• Released: several thousand sterile males at Terre-Cabade from 26 May 2026, rising to 200,000 a week.
• Scale-up: the wider treatment area around the cemetery.
• Result they are aiming for: up to an 80% cut in local tiger-mosquito numbers.
• The stated aim: the zone largely free of the mosquito within two years.
• Ground covered: the cemetery and a buffer around it in Toulouse.

Toulouse Métropole plans 200,000 sterile males a week from May to October, a sustained release rather than a single one. The programme is run by the specialist operator Terratis, which also runs the release in Montpellier's Malbosc district.

What "two years" is actually promising

The two-year figure needs conditions. Two years is roughly how long a sustained release of sterile males can take to suppress breeding in a defined zone. That holds provided each wave keeps pace with the wild population as it recovers, and provided the neighbourhood is not constantly re-seeded by tiger mosquitoes drifting in from untreated streets nearby.

That second condition is why Toulouse began in a cemetery. A contained site is the easiest place to keep the sterile males dense enough to matter, which is why it was chosen, and why it proves less than it appears. Suppressing the mosquito at Terre-Cabade does not suppress it across Toulouse. The real test is the wider rollout, when the same technique has to hold across a leakier, busier, more human map. A contained site is easier to treat than a porous city.

Why this is bigger than one French city

Two things lift Toulouse above the level of a municipal experiment.

The first is that it is not alone. France is running the sterile insect technique in more than one place, and not only in Toulouse. Montpellier and Brive-la-Gaillarde also have releases under way, each with its own numbers. Whether that becomes a national network or stays a set of separate city trials is the question to watch over the next two summers.

The second is money. Toulouse is paying for this itself, at the municipal level. The reason is arithmetic. Montpellier's Malbosc trial runs at roughly €70,000 to release 100,000 males twice a week across 31 locations. Scale that up to tens of millions of males a season across a whole city, every summer, and the figure is far above a current insecticide budget. Not yet.

The part that lands on your doorstep

The shape of it is simple: industrial sterile-mosquito releases are real, they are working where they have been tried, and they are still years away from covering a whole city.

For the next several summers, in Toulouse, Montpellier and Brive-la-Gaillarde, the people who live there still do most of the work. Not because the science is weak, but because it has not reached their street yet. Their gardens, their gutters and the screens on their windows are doing the work that a city-scale release will, one day, make lighter.

That is the case for combining measures. A tipped-out saucer of standing water removes a nursery the operators never have to treat. A screen on an open window is a barrier that does not wear off and does not need reapplying. It also does not depend on whether the release two streets over is on schedule. The advanced biology is one part of the response. The most dependable measure, the one in your own hands, is still a physical one.

The technique is sound, and the scale is honest. The two-year clock applies to the cemetery, at least.

What we know

• Terre-Cabade cemetery, in Toulouse, is the launch site of a sterile-male Aedes albopictus release that began on 26 May 2026. (Actu.fr / Toulouse Métropole, 26 May 2026)
• The first release ran to several thousand sterile males, with 200,000 a week planned; the plan is to scale up across the wider treatment area. (Actu.fr; Les Echos, 13 June 2026)
• The operator's target is up to an 80% reduction over two years in local tiger-mosquito numbers. (Actu.fr / Toulouse Métropole, 26 May 2026)
• The operator's stated aim is a zone largely free of the mosquito within two years. (Les Echos, 13 June 2026)
• The technique is being run by IRD-linked operators in Montpellier and other French cities. (AFP via Phys.org, 16 June 2026)

What to do

• If you live in or visit Toulouse: treat the cemetery and the streets around it as the trial ground, not the whole city. The scale-up has not been deployed beyond the cemetery buffer, so across the rest of the metro area the ordinary precautions still apply: repellent based on DEET or picaridin, long sleeves at dusk, and screens on the windows.
• If you live in Montpellier or Brive-la-Gaillarde: the releases in these cities run separately, each with its own numbers. Until a city-wide scale-up actually reaches your address, the reliable measure is the unglamorous one: empty the standing water, clear the gutter, screen the window.
• If you are reading from anywhere else: the technique travels, but not yet at city scale. If your local authority announces an SIT pilot, ask it three things: the reduction it is targeting, the release area in hectares, and the over-flooding ratio of sterile to wild males it is sustaining. A real release can give you all three. A press release that cannot is not, yet, a release.

Sources cited

1. Les Echos, "En deux ans, la zone est nettoyée : bientôt la fin des moustiques avec cette technique testée à Toulouse" (13 June 2026). https://www.lesechos.fr/idees-debats/sciences-prospective/en-deux-ans-la-zone-est-nettoyee-bientot-la-fin-des-moustiques-avec-cette-technique-testee-a-toulouse-2236608
2. Actu.fr, Toulouse piece on the 26 May 2026 launch. https://actu.fr/occitanie/toulouse_31555/ils-doivent-eradiquer-les-moustiques-tigres-de-toulouse-des-millions-de-moustiques-speciaux-vont-etre-relaches-en-ville_64314598.html
3. Toulouse Métropole, "La lutte contre les moustiques s'accélère" (official municipal page on the sterile-insect release run by the operator Terratis). https://metropole.toulouse.fr/actualites/la-lutte-contre-les-moustiques-saccelere
4. AFP via Phys.org, "Scaling up: Key French firm now breeds 1.5 million sterile mosquitoes a week" (16 June 2026). https://phys.org/news/2026-06-scaling-key-french-firm-sterile.html
5. European Centre for Disease Prevention and Control, "Aedes albopictus factsheet." https://www.ecdc.europa.eu/en/disease-vectors/facts/mosquito-factsheets/aedes-albopictus