The sterile insect technique uses radiation to stop Aedes mosquitoes from reproducing. European field trials in Germany, Greece, Spain and France show how well it works, and where it still depends on community consent.
What the sterile insect technique does
The sterile insect technique is insect birth control. Males are bred in a facility, separated from females, and sterilised with radiation. They are then released to mate with wild females, which lay eggs that never hatch, so the population falls over time. The World Health Organization describes the method this way in a news item published on 16 May 2023 about a project starting in French Polynesia. The same item notes that the technique has been used for 60 years against agricultural pests, including the Mediterranean fruit fly and the tsetse fly. A 16 year programme eradicated the tsetse fly from a 1,000 square kilometre area of Senegal. The method is species specific, so it targets one mosquito species and leaves other insects alone.
Why the tiger mosquito is a target
The tiger mosquito, Aedes albopictus, breeds in small containers close to people, which makes conventional spraying difficult. It also bites during the day. WHO puts dengue at an estimated 100 to 400 million infections a year, with about half the world population at risk, and calls community acceptance key to implementing the sterile insect technique. Aedes albopictus can carry dengue, chikungunya and Zika viruses. Resistance matters because it erodes the main chemical tool. WHO quotes Herve Bossin, principal investigator of the French Polynesia project, calling the sterile insect technique a promising alternative to insecticides. The technique does not add chemicals to the environment. Its limits are practical: it needs sustained releases, good sex separation, and enough sterile males to outnumber wild ones.
Mixed tactics in southwest Germany
Becker and colleagues described an integrated programme in southwest Germany in Parasites and Vectors on 5 January 2022. It combined community use of fizzy Bti tablets, door to door Bti treatment of breeding sites, and releases of irradiated sterile male Aedes albopictus. Male pupae aged 24 to 32 hours received 35 Gy from a caesium-137 gamma source. More than 310,000 sterile males were released in 18 weekly releases from 29 May to 7 October 2020 in the 17 hectare sterile insect technique sector of the Melm district of Ludwigshafen. Egg sterility reached 84.7 percent there, measured with a standard deviation of 12.5, against 14.6 percent natural sterility in the control area. The container index for the species fell from 10.9 percent in 2019 to under 1 percent in 2020.
Costs and access in the German trial
The German authors also reported the practical side. Sterile insect technique cost far more than the community measures at that stage. Community and door to door work cost about 13 euros per property, roughly sevenfold less than the sterile releases, though the authors say the higher figure reflected the experimental status of the project. Property access averaged 80 percent against a target of 95 percent, which shows how much the method depends on residents opening their doors. The authors conclude that an integrated programme works best with all three components together, and call Bti plus sterile insect technique the most effective and selective tool against Aedes albopictus. The trial was small, in two urban districts, so the numbers are a signal rather than a finished result.
Suppression in Greece
Balatsos and colleagues ran a suppression trial against Aedes albopictus in Greece, published in Parasite in 2024. Larvae were mass reared to international protocols from a colony founded on eggs collected at Vravrona. Males were irradiated as pupae at 35 Gy with a caesium-137 source in Italy, then transported about 21 hours to the release plot in Greece, with mean transport mortality of 16.19 percent. In total 585,810 sterile males were released over 22 weeks, a mean of 2,547 per hectare per week. Repeated releases produced a gradual fall in egg density reaching 78 percent from mid June to early September, and the reduction stayed between 70 and 78 percent for four weeks after releases ended. Seasonal average induced sterility was 48.87 percent. The authors call it the first attempt based on long distance production of sterile males.
Boosted releases in Spain and La Reunion
Bouyer and colleagues reported three boosted trials in Scientific Reports on 21 May 2025. Sterile males were coated with a powder of 40 percent pyriproxyfen and 60 percent fluorescent marker, so they also spread a larvicide. Two trials targeted Aedes albopictus in the Valencia Region of Spain across 2021. In La Vilavella, 3,892,075 males were released over 35 hectares, about 2,712 per hectare per week; in eastern Polinya de Xuquer, 2,470,465 males covered 23 hectares. Relative adult density fell to 0.02 and 0.11 against control sites. Relative egg density in eastern Polinya de Xuquer was 0.44. The authors note that high success required isolated or large areas, because fertile females can re-invade from untreated neighbours.
What residents need to know
The evidence points to a method that works best as part of a wider programme, not as a replacement for removing standing water and protecting homes. Results varied widely between sites, which reflects differences in mosquito density, area size, and release quality. All three field projects relied on people granting access to gardens and yards. WHO calls community acceptance key to implementing the sterile insect technique. In the German trial, access reached 80 percent against a 95 percent target. Aedes albopictus is a container breeder, so emptying water from pots, gutters, tarpaulins and discarded containers remains a direct form of control. Physical barriers such as intact screens and correctly specified nets also reduce bites. Ask your local health authority what measures are planned or running where you live. Readers who want the full detail can follow the supplied primary studies.
Sources
- Scientists in Tahiti prepare to release sterilized mosquitoes to control dengue: World Health Organization
- Integrated control of Aedes albopictus in Southwest Germany supported by the Sterile Insect Technique: Parasites and Vectors, via PubMed Central
- Sterile Insect Technique (SIT) field trial targeting the suppression of Aedes albopictus in Greece: Parasite, via PubMed Central
- Suppression of Aedes mosquito populations with the boosted sterile insect technique in tropical and Mediterranean urban areas: Scientific Reports, Nature Portfolio