Keywords: Irradiation method

Mark–release–recapture study of irradiated male Aedes albopictus under stressful field conditions

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Qingdeng Feng, Ming Li, Jeremy Bouyer, et al.,  Pest Management Science,  2026-03-09 10:33:54.
The sterile insect technique (SIT) suppresses mosquito populations by releasing sterile males. Its success mainly depends on the performance of sterile males. Mark–Release–Recapture (MRR) experiments are used to evaluate male performance in the field, yet most previous experiments were conducted under mild conditions (e.g. 25–28 °C) in which mosquitoes could easily adapt. Male mosquito performance under stressful field conditions remains poorly understood. This study evaluated the field performance of irradiated Aedes albopictus males under high-temperature conditions (>30 °C in average) in southern China, Foshan City, located in a sub-tropical area. Two MRR experiments were conducted in a 5-ha village during July–August of 2023 and 2024. Lifespan and dispersal of postreleased males were examined using BG-Sentinel mosquito traps, human landing catches, and ovitraps. A total of 54 546 and 58 440 sterile males were released in 2023 and 2024, respectively, with recapture rates of 8.53% and 5.64%. The mean dispersal distances ranged from 58.88–77.19 m (2023) to 81.82–90.86 m (2024). Daily survival probabilities were 0.15–0.28 in 2023 and 0.45–0.62 in 2024, corresponding to average expected lifespans of 0.53–0.78 days and 1.26–2.13 days, respectively. Estimated wild male densities ranged from 302–986 males ha−1 in 2023 to 416–3785 males ha−1 in 2024. Stressful field conditions severely reduced sterile male survival and dispersal, highlighting the need to optimize release protocols in challenging climates. These findings provide critical baseline data for advancing Ae. albopictus SIT programmes in southern China. 

Effect of male age at the time of irradiation on the sexual performance of sterile Ceratitis capitata males: insights from remating female offspring

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Edwin Mauricio Ramírez-Santos, Pedro Alfonso Rendón Arana, et al.,  Insect Science,  2025-11-03 11:19:51.
The Sterile Insect Technique (SIT) is an effective strategy for controlling insect pests, such as the Mediterranean fruit fly (Ceratitis capitata, Wiedemann). The effectiveness of the SIT depends on the ability of the sterile males to mate and their capacity to induce sterility in wild females. This study evaluated how the irradiation age affects their sexual performance, measured by the outcome of female remating events. Males of the GSS VIENNA 8D53− were irradiated at eleven different ages, from 72 h before emergence (pupal stage) to 72 h after emergence (adult stage) and mated with wild females. These females were subsequently allowed to mate with fertile males from the fluorescent TSS VIENNA 8 1260. The presence of fluorescent offspring was used as indicator of second-male paternity. Results showed that males irradiated at post-emergence ages produced the lowest egg-to-pupae conversion rate, indicating a greater ability to prevent females from producing offspring after remating with a fertile male. In contrast, males irradiated at pre-emergence ages were associated with higher numbers of fluorescent offspring. Although no significant differences were found in mating competitiveness (RSI), the outcome of the remating showed differences in the effectiveness of initial matings. These findings highlight the importance of considering the age of flies at time of irradiation in mass-rearing protocols to enhance the efficacy of SIT programs targeting C. capitata and suggest that irradiating males later in their life cycle, such as adult stages or in pupae close to adult emergence, limit offspring if females remate with fertile males in the field.

Effect of egg irradiation on development and sterility of wild-type and Wolbachia trans-infected Aedes aegypti mosquito vectors

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Kittayapong P, Ninphanomchai S, Thayanukul P, Limohpasmanee W,  PLoS One,  20. 2025-09-26 13:56:46.
Sterile Insect Technique (SIT), Incompatible Insect Technique (IIT) or a combination of the two has become alternative promising vector control approaches. In order to apply these approaches, the targeted mosquitoes need to be sterilized and released. So far, the irradiation of mosquitoes has been conducted at the pupae or adult stages. In this study, we investigated the possibility of applying X-ray irradiation at the egg stage and also assessed the effect on the development and sterility of both wild-type and Wolbachia trans-infected Aedes aegypti mosquito vectors. The eggs of both wild-type and Wolbachia trans-infected lines were irradiated using X-ray at the doses of 1, 3, 5 and 7 Gy. Development of immature stages was observed. For wild-type Ae. aegypti, X-ray irradiation at the doses from 3 Gy decreased the development of the first-instar larvae and increased the development of the third-instar larvae but there was no effect on pupae. For Wolbachia trans-infected ones, a irradiation dose as low as 1 Gy could increase the development of the forth-instar larvae while an irradiation dose of 7 Gy induced significantly high mortality to the pupae (p < 0.05). To assess sterility, males and females that emerged from irradiated eggs were mated with the non-irradiated ones. Our results showed that an irradiation dose of 7 Gy significantly caused more than 90% sterility in both wild-type males and females (p < 0.05). However, this irradiation dose could be reduced to 5 Gy to sterilize both males and females infected with Wolbachia. Our findings revealed, for the first time, that applying a low-dose X-ray irradiation at the egg stage could sterilize both wild-type and Wolbachia trans-infected Ae. aegypti when they become adults. Egg irradiation could make the implementation of SIT, IIT or combined SIT/IIT for vector control much more feasible as the sterile eggs are easier to distribute and operate when compared to other developmental stages of mosquitoes.

Application of Sterile Insect Technique (SIT) for Aedes albopictus (Skuse, 1895) in Sri Lanka: Dose optimization, mating competitiveness and release ratios

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Harishchandra J, Abeyewickreme W, Premaratne R, Hapugoda M,  PLoS One,  20. 2025-09-05 08:04:10.
Sri Lanka has experienced severe dengue epidemics in recent years, despite the extensive vector control measures taken. Therefore, it is necessary to find sustainable vector control strategies against dengue. Novel vector control tools need to be tested for the feasibility of applying them against local vectors. Sterile Insect Technique (SIT) is an increasingly popular vector control technique which has been adopted by many countries to suppress insect pest populations and is being tested for dengue vectors. In this study, SIT was developed for Aedes albopictus (Skuse, 1895), one of the 2 dengue vectors present in Sri Lanka. The optimum radiation dose for sterilizing male pupae (age 24–48 hours) using a Co 60 source was determined based on the post-irradiation pupal and adult survival in males and induced sterility in females at different doses. Further, the effect of irradiation on mating competitiveness of the selected mosquito strain was assessed under laboratory and semi-field conditions. The optimum release ratio of irradiated males to wild males was assessed in laboratory and semi-field settings. The optimum radiation dose was 50 Gy among the series of doses (25, 30, 40, 50, 60, and 70 Gy) tested. When pupae were exposed to the optimal radiation dose, 100% pupal survival, 19-day median adult survival time and 99% induced sterility resulted. A 5:1 ratio of irradiated males to non-irradiated laboratory-reared or wild males in laboratory cages resulted in induced sterility of 75% and 62%, respectively. The respective values were 74% and 61% in large semi-field cages. Fried Competitiveness Index (FCI) of irradiated males against wild males of laboratory and wild origin were 0.63 and 0.43 in laboratory cages and 0.57 and 0.55 in large semi-field cages. The males of Ae. albopictus irradiated at 50 Gy are adequately sterile and are competitive against the wild males. The release ratio of 5:1 irradiated males to wild males is a suitable ratio for the field application of SIT. The findings of the study will be important for the development of a protocol for future application of SIT for Ae. albopictus in Sri Lanka.

Vector Control District Plans Experimental Mosquito Control Program

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Contributing Editor,  MyNewsLA.com,  2025-07-24 09:51:29.
Batches of irradiated male mosquitoes are slated for release Wednesday in Lake Elsinore with the goal of pairing the modified insects with as many females as possible to kill off the overall mosquito population, under an experimental program that apparently hasn’t generated concerns among public officials. The “Sterile Insect Technique Pilot Program” is being managed by the Northwest Mosquito & Vector Control District, which serves segments of western Riverside County. The district is believed to be the first countywide to inaugurate an SIT mosquito control program. Questions regarding when it was authorized, the estimated number of modified mosquitoes that will be released and any potential public health risks were not answered by the agency as of Tuesday afternoon. Lake Elsinore officials also did not respond to requests for comment. The West Valley Mosquito & Vector Control District, which encompasses Ontario, Montclair and neighboring municipalities in San Bernardino County, was the first district in California to receive authorization from state regulators to initiate mosquito SIT releases last year, under a pilot program similar to that of the Northwest Mosquito & Vector Control District. It’s still unknown whether West Valley’s experimental program has netted any benefits. “Sterile male mosquitoes are released to mate with local females, and the resulting eggs are unable to hatch,” NMVCD said in a statement regarding the Lake Elsinore program. “The release of adult male mosquitoes will not increase local bite pressure, as only female mosquitoes bite.”

Evaluating the impact on F1 sterility of tsetse pupae Glossina morsitans morsitans irradiated following short-term hypoxic conditioning

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Caroline K. Mirieri, Kiswend-sida M. Dera, Vanessa S. Dias, et al,  Insect Science,  2025-05-26 20:07:11.
The sterile insect technique (SIT) for tsetse involves releasing sterilized males to outcompete wild males in mating, resulting in nonviable progeny. Balancing optimum sterility and male quality is crucial. While irradiation in hypoxia or anoxia is routine for tephritid flies, its effect on tsetse, especially postrelease, is not well understood. We conducted experiments to understand the impact of irradiation in hypoxia on the sterility of the F1 generation of Glossina morsitans morsitans (Gmm). Initially, we tested the impact of 1-h preconditioning in hypoxia before irradiation and continued hypoxia up to 24, 48, and 72 h postirradiation on the emergence and flight propensity of treated males. We then assessed mating ability, survival, pupae per initial female (PPIF) and residual fertility of flies following irradiation at various doses after 1-h hypoxia conditioning. Finally, we determined the PPIF and residual fertility of the F1generation and the emergence of treated flies to the F2 generation. Results show that short-term conditioning (1 h) in hypoxia maintains or improves the qualities of the irradiated Gmm pupae. Regardless of irradiation in normoxia or hypoxia, higher residual fertility was observed in females than males in the F0 generation, and higher residual fertility in the F1 than the F0 generation for both sexes. However, the emergence rates of males decreased in the F2 generation compared with the F1 generation, a noteworthy finding for SIT programs for tsetse, implying diminishing populations of sterile flies.

Upscaling irradiation protocols of Aedes albopictus pupae within an SIT program in Reunion Island

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Lucie Marquereau, Hanano Yamada, David Damiens, Antonin Leclercq, Brice Derepas, Cécile Brengues , Brice William Dain , Quentin Lejarre 1, Mickael Proudhon , Jeremy Bouyer and Louis Clément Gouagna,  Scientific Reports,  14:12117. 2025-02-03 07:03:06.
The implementation of the sterile insect technique against Aedes albopictus relies on many parameters, in particular on the success of the sterilization of males to be released into the target area in overflooding numbers to mate with wild females. Achieving consistent sterility levels requires efficient and standardized irradiation protocols. Here, we assessed the effects of exposure environment, density of pupae, irradiation dose, quantity of water and location in the canister on the induced sterility of male pupae. We found that the irradiation of 2000 pupae in 130 ml of water and with a dose of 40 Gy was the best combination of factors to reliably sterilize male pupae with the specific irradiator used in our control program, allowing the sterilization of 14000 pupae per exposure cycle. The location in the canister had no effect on induced sterility. The results reported here allowed the standardization and optimization of irradiation protocols for a Sterile Insect Technique program to control Ae. albopictus on Reunion Island, which required the production of more than 300,000 sterile males per week.