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 science works, an IRD entomologist 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 home front are the same answer.
On an industrial estate near Montpellier, a company called Terratis, founded only in 2024, is breeding mosquitoes in order to beat them. It rears male tiger mosquitoes by the hundred thousand, passes their pupae under an X-ray beam 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 folds.
Terratis now makes 1.5 million of these sterile males a week. It intends to make 40 million. That is the most aggressive industrial run at the sterile insect technique (SIT) against Aedes albopictus anywhere in Europe, and one of only about 50 comparable projects on Earth.
The technique is old; the hard part is new. The International Atomic Energy Agency has funded sterile-insect programmes since the 1960s, when the targets were crop pests, not 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, an entomologist at France's IRD (the Institut de Recherche pour le Développement) 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 released from May 2025 rendered half of that spring's eggs infertile, and Clelia Oliva, the company's founder and public face, projects 90% by the end of summer 2026. What it has not done is hold a whole city, which is what it is now being asked to do for the first time. It also falls into a regulatory gap, counted as neither a biocide nor a genetically modified organism, so neither France nor Europe has written a clean approval pathway for it. And Simard is candid that the sterile male is not a solo act: it "needs to be combined" with other methods, and he calls the rival Wolbachia technique an "emergency response" rather than a long-term strategy.
The two approaches are cousins, not twins. A Wolbachia male carries a bacterium that either kills its offspring or leaves them unable to transmit dengue; an X-rayed male carries no viable future at all. Both shrink mosquito populations, both have their advocates, both come with technical and regulatory snags. Brazil already runs a single Wolbachia facility that produces 100 million infected eggs a week, 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 gets to 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 wall 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.
There is a smaller figure that matters as much as the large ones. Four in five tiger mosquitoes in France, Midi Libre reports, hatch not in distant marshland but in private gardens: the saucer under a flowerpot, a blocked gutter, a bucket left out in the rain. In Pérols, just outside Montpellier, an entomologist named Julien Mocq, of the firm Altopictus, has been holding public meetings to show 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 are right. Both are the same answer.
Why the factory and the garden are not rivals
The tiger mosquito is now established in 83 of France's 96 metropolitan departments, according to Le Parisien, and its biting season has stretched to run from May to November. No city anywhere has yet swapped household protection for sterile-male releases, and none will this summer. Until the day a whole city is covered, the layer you can count on is the one within reach: the screen on the window, the repellent at dusk, the two minutes it takes to tip out standing water. Physical barriers and small routines are the durable household layer; industrial releases are the area-scale layer above it. They are complements, not substitutes.
Clelia Oliva describes her aim as "not to eradicate the species entirely, but to significantly and sustainably reduce their numbers". It is worth noticing that this is also a fair description of what one well-kept garden does, week after week. The factory and the home front were never two answers to the tiger mosquito. They were always the same one.
What to do
- If you live in one of the 83 French departments where the tiger mosquito is established: treat the sterile-male factory as good news that has not arrived yet. The layer 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 biting season now running May to November, that is a five-month habit, not a one-week one.
- If you live in a pilot city (Montpellier, Toulouse, Brive-la-Gaillarde or La Verpillière): 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 are complements, not substitutes.
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
- 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