In two years a Montpellier firm, Terratis, has scaled from nothing to 1.5 million sterile male tiger mosquitoes a week, with a target of 40 million. The technique works, the head of the IRD in Montpellier calls it 'iPhone 1.0 stage', but no French city can yet afford to cover itself, and four in five tiger mosquitoes still hatch in private gardens. The factory and the household point to the same answer.
On an industrial estate near Montpellier, a company called Terratis, founded in 2024, is breeding mosquitoes to reduce their numbers. It rears male tiger mosquitoes by the hundred thousand, exposes the adult males to X-rays in batches of about 400,000, and ships the survivors to French cities. The radiation does one thing: it leaves the males alive, active and ready to mate, but unable to produce viable young. Release enough of them and the wild females they mate with lay eggs that never hatch. Over a few generations, the local population declines.
Terratis now makes 1.5 million of these sterile males a week, and aims to reach 40 million within two years. That is one of the largest industrial efforts using the sterile insect technique (SIT) against Aedes albopictus in Europe, and one of about 50 comparable projects worldwide.
The technique is old; the hard part is new. It was first developed about fifty years ago for agriculture, against crop pests rather than mosquitoes. A mosquito, though, is smaller and more delicate than a fruit fly and much harder to rear by the million, and only recently has the factory engineering caught up with the biology.
It works. It is not finished.
Ask how well it works and you get an unusually honest answer. Frederic Simard, head of the Institute of Research for Development (IRD) in Montpellier, puts the technology at "iPhone 1.0 stage". It works. It is not finished.
Every part of that verdict holds up. In contained trials the method has already delivered. At Brive-la-Gaillarde, 11 million sterile males were released from May 2025, and half of that spring's eggs were sterile. Clelia Oliva, the company's co-founder, says the figure should reach 90% by the end of summer 2026. What it has not done is cover a whole city, which is what it is now being asked to do for the first time. It also falls into a regulatory grey area in France. It is counted as neither a biocide nor a genetically modified organism, so France has not written a clear approval pathway for it. Simard is clear that the sterile male is not a stand-alone method. It "needs to be combined" with other methods, and he calls the Wolbachia technique an "emergency response" rather than a long-term strategy.
The two approaches are related but distinct. A Wolbachia male carries a bacterium that either prevents its offspring from hatching or stops them transmitting dengue. An X-rayed male produces no viable offspring at all. Both reduce mosquito populations, both have their advocates, and both come with technical and regulatory questions. Brazil already runs a single Wolbachia facility that produces as many as 100 million eggs a week. It is a different technique, on a different continent, at a scale that shows where the industry can go. Terratis's 40-million target would reach that league by another road. Montpellier is, in part, a live test of which method reaches city scale first.
The number the announcements skip
Then there is the figure the announcements tend to leave out: the cost. In the Malbosc district of Montpellier, a trial running since August 2025 releases 100,000 sterile males twice a week across 31 sites, at a cost of about €70,000 ($81,000). That buys one district. "We don't have the means to finance releases on the scale of an entire city," Montpellier's deputy mayor, Stephane Jouault, told AFP. The same limit appeared around Toulouse's programme in June: the town hall pays, the regional health agency (ARS) does not. The science works at the scale of a district; the money to cover a city does not yet exist. A national sterile-mosquito programme will need someone, somewhere, to sign a national cheque.
One smaller figure matters as much as the large ones. Four in five tiger mosquitoes in France, Midi Libre reports, hatch in private gardens rather than distant marshland: the saucer under a flowerpot, a blocked gutter, a bucket left out in the rain. In Pérols, just outside Montpellier, Julien Mocq has been holding public meetings. He is a doctor of entomology with the firm Altopictus, and he shows residents the breeding sites they walk past without seeing. So one department now holds both a factory that makes a million mosquitoes a week and a public meeting about a single bucket of standing water. Both facts point to the same conclusion.
Why the factory and the garden work together
The tiger mosquito is now present across most of France, and in temperate Europe it is active for more than eight months of the year. No city anywhere has yet replaced household protection with sterile-male releases, and none will this summer. Until a whole city is covered, the protection you can count on is the one within reach: the screen on the window, the repellent at dusk, and the two minutes it takes to tip out standing water. Physical barriers and small routines are the durable household measures; industrial releases are the area-scale response above them. The two work together, and neither replaces the other.
Clelia Oliva describes her aim as not to remove the species entirely, but to reduce its numbers significantly and sustainably. That is also a fair description of what one well-kept garden does, week after week. The factory and the household were never two separate answers to the tiger mosquito. They were always the same one.
What to do
- If you live in a part of France where the tiger mosquito is established: treat the sterile-male factory as good news that has not arrived yet. The protection you can rely on today is personal: a DEET- or picaridin-based repellent at peak biting times, long sleeves at dusk, and screens on windows and doors. With the active season now running for much of the year, that is a sustained habit, not a one-week one.
- If you live in a pilot city (Montpellier, Toulouse or Brive-la-Gaillarde): the release near you is real, but it is funded by the town hall and runs at district scale, not across the city. Your garden, your gutters and your screens still do most of the work. Remember the number: four in five tiger mosquitoes start life in a private garden.
- If your commune calls a public meeting about the tiger mosquito: the useful question is not "is a release coming?" but "what is the schedule, what is the published reduction target, and what is the budget line?" A genuine release publishes all three. A press release that does not is not yet a release.
- If you are reading from outside France: the same logic travels. The technique is portable, but no city anywhere has replaced household protection with sterile-mosquito releases at city scale. The two work together, and neither replaces the other.
Sources cited
- 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
- France 24, "Stériliser le moustique tigre : le pari incertain d'une protection industrielle" (16 June 2026). https://www.france24.com/fr/info-en-continu/20260616-st%C3%A9riliser-le-moustique-tigre-le-pari-incertain-d-une-protection-industrielle
- Midi Libre, "Environ 80% des moustiques tigres proviennent de jardins privés : un expert explique comment limiter leur prolifération" (17 June 2026). https://www.midilibre.fr/2026/06/17/environ-80-des-moustiques-tigres-proviennent-de-jardins-prives-un-expert-explique-comment-limiter-leur-proliferation-13424067.php
- European Centre for Disease Prevention and Control, "Aedes albopictus factsheet." https://www.ecdc.europa.eu/en/disease-vectors/facts/mosquito-factsheets/aedes-albopictus
- Euronews via MSN, "France is releasing millions of sterile insects to fight tiger mosquitoes" (17 June 2026). https://www.msn.com/en-in/science/biology/france-is-releasing-millions-of-sterile-insects-to-fight-tiger-mosquitoes/vi-AA25Qwgv