Toulouse released sterile mosquitoes in a cemetery. Five million is the target.

On 26 May 2026, in the Terre-Cabade cemetery in the north of Toulouse, a field team opened a set of small containers and let several hundred thousand mosquitoes go. Every one was male. Every one was sterile. And every 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. The operators intend to scale the release across the wider treatment area to five million sterile males, and on 13 June, in a follow-up in Les Echos, they made the promise of the year: "in two years, the zone is cleaned."

How you fight a mosquito with a mosquito

The logic is old and elegant. Only the female bites, and she is the one the sterile males are for. Release enough of them to swamp 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 folds in on itself.

Producing those males is the hard part. In a dedicated facility, male pupae are given a measured dose of ionising radiation, most often X-rays, sometimes gamma, calibrated to wreck the sperm without otherwise harming the insect. The survivors are sorted, packed, and set loose by ground teams or by drone. No insecticide touches the ground. Nothing is genetically modified. And the fix cancels itself out: the released males die within days, and the eggs they leave behind never open. It is the same principle that has held the Mediterranean fruit fly and other agricultural pests in check for decades, now pointed at the mosquito on your ankle.

One scientist at France's IRD (Institut de Recherche pour le Développement), which has been piloting the method in Montpellier, called the wider French effort "iPhone 1.0 stage": the idea is proven, 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 hundred thousand sterile males, at Terre-Cabade, from 26 May 2026.
• Scale-up target: five million sterile males across the treatment area.
• Result they are aiming for: an 80% cut in local tiger-mosquito numbers.
• The headline promise: the zone "cleaned" within two years.
• Ground covered: the cemetery and a buffer around it in northern Toulouse. The exact area in hectares has not been made public.

The five-million figure is the one that travels, so it is worth being plain about what it is: a target for a sustained campaign, not a single grand release. The programme is run by the specialist operator Terratis, and one of its directors, Christophe Privat, called it "an innovative approach that has had good results," pointing to published evidence that it works at scale. He said good results. He did not say victory, and the distance between those two phrases is the whole story.

What "two years" is actually promising

Read the promise closely and it holds up, with conditions. Two years is roughly how long a sustained flood of sterile males can take to collapse breeding in a defined zone, 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 thick enough on the ground to matter, which is exactly why it was chosen, and exactly why it proves less than it appears. Clearing Terre-Cabade does not clear Toulouse. The real test is the five-million rollout, when the same technique has to hold together across a leakier, busier, more human map. A contained site keeps a release together. A porous city pulls it apart.

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 quietly running the sterile insect technique in more than one place, and not only in Toulouse. Montpellier, Brive-la-Gaillarde and La Verpillière all have releases under way, each publishing its own numbers. Whether that adds up to a national network or just three cities testing the same thing separately is the question worth watching across the next two summers.

The second is money, and this is where the honesty gets sharp. Toulouse is paying for this itself, at the municipal level. France has no national budget for the sterile insect technique, and deputy mayors in the other pilot cities have said out loud that the state and the regional health agencies, the ARS, should be carrying the cost. The reason is arithmetic. Montpellier's Malbosc trial runs at roughly €70,000 to release 100,000 males twice a week across 31 locations. Multiply that out to tens of millions of males a season, across a whole city, every summer, and you are nowhere near a figure that replaces an insecticide budget. Not yet.

The part that lands on your doorstep

So here is the honest shape of it, in a single line: 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 and Montpellier and Brive-la-Gaillarde and La Verpillière, the people who live there are still the front line. 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 five million sterile males will, one day, make lighter.

That is the case for layered control, and it is not a slogan. 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, does not need reapplying, and does not care whether the release two streets over is on schedule. The clever biology is the top layer. The dependable layer, the one in your own hands, is still a physical one.

There is a reason Christophe Privat said "good results" and not "done." The technique is sound. The scale is honest. The clock is two years, for the cemetery at least.

What we know

• Terre-Cabade cemetery, in northern 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 hundred thousand sterile males; the planned scale-up is five million across the treatment area. (Les Echos, 13 June 2026)
• The operator's target is an 80% reduction in local tiger-mosquito numbers. (Actu.fr / Toulouse Métropole, 26 May 2026)
• The operator's most-quoted claim is that "in two years, the zone is cleaned." (Les Echos, 13 June 2026)
• Christophe Privat, a director of the operating programme, has publicly called the release "an innovative approach that has had good results." (Coverage of the 26 May 2026 launch)
• The technique is being piloted by IRD-affiliated operators in Montpellier and other French cities.

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 five-million scale-up has not been deployed beyond the cemetery buffer, so across the rest of the metro area the ordinary defences still apply: repellent based on DEET or picaridin, long sleeves at dusk, and screens on the windows.
• If you live in Montpellier, Brive-la-Gaillarde or La Verpillière: the releases in these cities run in parallel, not stacked on top of one another, and there is no national budget behind them. Until a city-wide scale-up actually reaches your address, the reliable layer 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