Sterile Insect Technique Research Articles

Sperm Storage and Use Following Multiple Insemination in Aedes albopictus: Encouraging Insights for the Sterile Insect Technique

The key to success in the application of the sterile insect technique (SIT) relies on the ability of released, sterile males to outcompete their fertile wild male counterparts to mate with wild females. However, many insect species exhibit multiple-mating behavior, which can be a way for females to select paternity for their progeny. This study aims to recognize the consequences of potential double-matings during an SIT program and to detect any evidence of sperm selection favoring sperm from fertile mates. This report provides a descriptive analysis of the storage and use of sperm by female Aedes albopictus. Stable isotopes were used to mark the sperm of fertile and sterile males. Mated females were allowed to oviposit before dissecting the spermathecae to link the presence of each type of sperm to the sterility of the eggs laid. It was found that sperm in females inseminated by both males was distributed in the three spermathecae with no obvious pattern, mostly mixed but also separately, and no evidence of any mechanism for sperm selection, sperm precedence, or sperm competition in Ae. albopictus females could be found. The fact that only a few double-mated females were double-inseminated and could also produce semi-sterile eggs, together with the finding that the sperm of sterile males appeared to be no less viable than that of fertile males, is an encouraging outcome for SIT approaches.

Population suppression with dominant female-lethal alleles is boosted by homing gene drive

BackgroundMethods to suppress pest insect populations using genetic constructs and repeated releases of male homozygotes have recently been shown to be an attractive alternative to older sterile insect techniques based on radiation. Female-specific lethal alleles have substantially increased power, but still require large, sustained transgenic insect releases. Gene drive alleles bias their own inheritance to spread throughout populations, potentially allowing population suppression with a single, small-size release. However, suppression drives often suffer from efficiency issues, and the most well-studied type, homing drives, tend to spread without limit.ResultsIn this study, we show that coupling female-specific lethal alleles with homing gene drive allowed substantial improvement in efficiency while still retaining the self-limiting nature (and thus confinement) of a lethal allele strategy. Using a mosquito model, we show the required release sizes for population elimination in a variety of scenarios, including different density growth curves, with comparisons to other systems. Resistance alleles reduced the power of this method, but these could be overcome by targeting an essential gene with the drive while also providing rescue. A proof-of-principle demonstration of this system in Drosophila melanogaster was effective in both biasing its inheritance and achieving high lethality among females that inherit the construct in the absence of antibiotic.ConclusionsOverall, our study shows that substantial improvements can be achieved in female-specific lethal systems for population suppression by combining them with various types of gene drive.

CRISPR/Cas12a ribonucleoprotein mediated editing of tryptophan 2,3-dioxygenase of Spodoptera frugiperda.

In insect genome editing CRISPR/Cas9 is predominantly employed, while the potential of several classes of Cas enzymes such as Cas12a largely remain untested. As opposed to Cas9 which requires a GC-rich protospacer adjacent motif (PAM), Cas12a requires a T-rich PAM and causes staggered cleavage in the target DNA, opening possibilities for multiplexing. In this regard, the utility of Cas12a has been shown in only a few insect species such as fruit flies and the silkworm, but not in non-model insects such as the fall armyworm, Spodoptera frugiperda, a globally important invasive pest that defies most of the current management methods. In this regard, a more recent genetic biocontrol method known as the precision-guided sterile insect technique (pgSIT) has shown successful implementation in Drosophila melanogaster, with certain thematic adaptations required for application in agricultural pests. However, before the development of a controllable gene drive for a non-model species, it is important to validate the activity of Cas12a in that species. In the current study we have, for the first time, demonstrated the potential of Cas12a by editing an eye color gene, tryptophan 2,3-dioxygenase (TO) of S. frugiperda by microinjecting ribonucleoprotein complex into pre-blastoderm (G0) eggs. Analysis of G0 mutants revealed that all five mutants (two male and three female) exhibited distinct edits consisting of both deletion and insertion events. All five edits were further validated through in silico modeling to understand the changes at the protein level and further corroborate with the range of eye-color phenotypes observed in the present study.

CRISPR/Cas9-Based Genome Editing of Fall Armyworm (Spodoptera frugiperda): Progress and Prospects

The fall armyworm (Spodoptera frugiperda) poses a substantial threat to many important crops worldwide, emphasizing the need to develop and implement advanced technologies for effective pest control. CRISPR/Cas9, derived from the bacterial adaptive immune system, is a prominent tool used for genome editing in living organisms. Due to its high specificity and adaptability, the CRISPR/Cas9 system has been used in various functional gene studies through gene knockout and applied in research to engineer phenotypes that may cause economical losses. The practical application of CRISPR/Cas9 in diverse insect orders has also provided opportunities for developing strategies for genetic pest control, such as gene drive and the precision-guided sterile insect technique (pgSIT). In this review, a comprehensive overview of the recent progress in the application of the CRISPR/Cas9 system for functional gene studies in S. frugiperda is presented. We outline the fundamental principles of applying CRISPR/Cas9 in S. frugiperda through embryonic microinjection and highlight the application of CRISPR/Cas9 in the study of genes associated with diverse biological aspects, including body color, insecticide resistance, olfactory behavior, sex determination, development, and RNAi. The ability of CRISPR/Cas9 technology to induce sterility, disrupt developmental stages, and influence mating behaviors illustrates its comprehensive roles in pest management strategies. Furthermore, this review addresses the limitations of the CRISPR/Cas9 system in studying gene function in S. frugiperda and explores its future potential as a promising tool for controlling this insect pest.

Optimizing and synchronizing Aedes aegypti colony for Sterile Insect Technique application: Egg hatching, larval development, and adult emergence rate

Mosquito Sterile Insect Technique (SIT) programs can be developed in smaller agencies through synchronization of the colony development to take advantage of the natural male early emergence. This paper examined key aspects of Ae. aegypti colony synchronization work, including egg hatching, larval development, and adult emergence to produce sufficient numbers of adult male mosquitoes within a specific timeframe for irradiation and release. Our data indicated that a relatively low percentage of males are required for colony propagation. Additional results highlighted that fresher Ae. aegypti eggs could yield as high as a 93 % hatching success than older eggs when placed under vacuum pressure in yeast infused water for 1.5 h. Eggs that were one-month old hatched (93 %) better than older eggs (0–32 %). A higher egg density in the hatching flask was correlated to a lower hatch rate, and higher larval density was related to unsynchronized pupae and delayed adult emergence. By keeping Ae. aegypti larvae at reasonable density, over 95 % of adults emerged on the first two days of emergence – indicating a high synchronicity. A standardized colony maintenance protocol therefore renders a synchronized larval development and adult male emergence which are critical in SIT programs.

Preparation for targeted sterile insect technique to control invasive Aedes aegypti (Diptera: Culicidae) in southern California: dose-dependent response, survivorship, and competitiveness.

Aedes aegypti is fast spreading across California, with over 300 cities within 22 central and southern counties being infested since its introduction in 2013. Due to its cryptic breeding habitats, control efforts have not been successful so far. This calls for innovative tools such as sterile insect technique (SIT) to reinforce the existing integrated pest management (IPM). Here, we assessed fitness, survivorship, and dose response of X-ray irradiated male Ae. aegypti in California. Locally acquired Ae. aegypti eggs were hatched and reared in temperature-controlled laboratory setting at the West Valley Mosquito and Vector Control District in Ontario, California. Freshly emerged adult male mosquitoes were manually separated using motor-operated aspirators and treated with X-ray radiation at different dosage (42-60 Gy). Dose response of irradiated males was analyzed and induced sterility determined. Survivorship of males treated with different X-ray doses was compared. Fecundity of females that mated with irradiated males at different X-ray doses was generally comparable. Overall, induced sterility increased with higher X-ray doses. Nulliparous females that mated with male Ae. aegypti treated with 55-60 Gy laid eggs with over 99% sterility. Non-irradiated male mosquitoes had higher survivorship (mean = 0.78; P = 0.0331) than irradiated mosquitoes (mean range = 0.50-0.65). The competitiveness index of irradiated males decreased with increasing X-ray treatment doses, 1.14 at 55 Gy and 0.49 at 60 Gy, and this difference was significant (P < 0.01). Irradiated males showed high survivorship and competitiveness-key for the anticipated SIT application for the control of invasive Ae. aegypti in California.

Evaluating impacts of radiation-induced sterilization on the performance and gut microbiome of mass-reared Mediterranean fruit fly (Ceratitis capitata) in Hawai'i.

Sterile insect technique (SIT) is a useful strategy for preventing and mitigative establishment of invasive insect species. SIT of the pest tephritid Mediterranean fruit fly, Ceratitis capitata (Wiedemann, 1824)WiedemannWiedemann, has been effective in preventing population establishment in vulnerable agricultural areas of the United States. However, irradiation-induced sterilization can have detrimental impacts resulting in reduced performance metrics. Mediterranean fruit fly males reared for SIT have been shown to have differences in their microbiomes relative to other population sources, which has been postulated to be a factor in how well flies compete with wild conspecifics. To identify baseline performance metrics on the effects of irradiation on the gut microbiome of mass-reared flies in Hawai'i, a study was performed to assess performance metrics and microbiome (bacterial 16S rRNA) variation across multiple timepoints. Mediterranean fruit fly pupae were selected from mass-reared trays intended for release, and paired samples were either irradiated or remained as controls and transported to the laboratory for evaluation. Irradiated flies exhibited fewer successful fliers, more rapid mortality rates, and were less active relative to control nonirradiated flies. Contrary to initial expectations, irradiation did not exert substantial impacts on the composition or diversity of bacterial reads. Samples were primarily comprised of sequences classified as Klebsiella and there were low levels of both read and taxonomic diversity relative to other 16S surveys of medfly. Although this study does not demonstrate a strong effect of irradiation alone on the Mediterranean fruit fly microbiome, there are several explanations for this discrepancy.

Gamma-Irradiated Female Aedes aegypti Mosquitoes Exhibit Greater Susceptibility to Mayaro Virus.

Mayaro virus (MAYV) is an alphavirus endemic in many parts of Central and South America transmitted to humans by Aedes aegypti. Currently, there is no vaccine or treatment of Mayaro infection, and therefore it is essential to control transmission by reducing populations of Ae. aegypti. Unfortunately, Ae. aegypti are extremely difficult to control with traditional integrated vector management (IVM) because of factors such as growing resistance to a dwindling list of registered insecticides and cryptic immature and adult habitats. The sterile insect technique (SIT) by irradiation is gaining traction as a novel supplemental tool to IVM. The SIT is being used operationally to release large numbers of sterilized colony-reared male mosquitoes in an intervention area to overwhelm females in the natural population, eventually causing population decline because of high frequencies of unfertilized eggs. However, little is known about the effect of irradiation on vector competence for mosquito-borne viruses such as MAYV in females that may be accidentally reared, irradiated, and released alongside males. In this investigation, we exposed female Ae. aegypti pupae to radiation and evaluated vector competence after inoculation with MAYV. Infection and dissemination rates of irradiated (10 and 40 Gy) Ae. aegypti were higher than those of non-irradiated cohorts at 7 and 14 days after infection. Although these results indicate a need to maintain effective sex sorting prior to irradiation and release of Ae. aegypti, our results are consistent with several previous observations that vectorial capacity and vector competence are likely lower in irradiated than in nonirradiated females.

Rhodamine-B for the mark, release, and recapture experiments in gamma-irradiated male Aedes aegypti (Diptera: Culicidae): Persistence, dispersal, and its effect on survival

Background and Aim: Rhodamine-B (Rh-B) marking shows a great potential for use in mark-release-recapture (MRR) studies for rear-and-release mosquito control strategies, including the radiation-based sterile insect technique. However, its applicability and evaluation in body-stain-irradiated males of Aedes aegypti have received little attention. The present study evaluated the use of Rh-B to mark gamma-irradiated male A. aegypti. Materials and Methods: Male A. aegypti were irradiated at the pupal stage at a dose of 70 Gy. After emergence, males were fed 0.1, 0.2, 0.3, or 0.4% Rh-B in 10% glucose solution for 4 days. Groups of unirradiated males that received the same feeding treatments were used as control groups. We evaluated the persistence of Rh-B and the longevity of males after Rh-B feeding. Furthermore, the use of Rh-B in irradiated A. aegypti for MRR experiments was evaluated at an urban site. Results: No difference was observed in the Rh-B persistence among all concentrations at the 24-h postmarking period ranging from 91.25 ± 1.61% to 96.25 ± 1.61% and from 90.00 ± 2.28% to 93.13 ± 2.77% for the unirradiated and irradiated groups, respectively. Rh-B persistence significantly decreased over time, and persistence was significantly longer with increased concentrations in both the unirradiated and irradiated groups. Longevity was considerably decreased by Rh-B feeding and irradiation. However, no significant difference in longevity was found among males fed various concentrations of Rh-B. Through MRR experiments, irradiated-Rh-B marked males were mostly detected within a radius of 20 m and 40 m from the center-release point. The mean distance traveled of the released males from the three MRR events was calculated to be 42.6 m. Conclusion: This study confirms that Rh-B body marking through sugar feeding is applicable for irradiated male A. aegypti, with only a slight effect on longevity. Furthermore, considering the significant reduction in persistence over time, further study is needed to assess the impact of this reduction on the calculation of field biological parameters resulting from MRR experiments. Keywords: irradiated males, mark-release-recapture, rhodamine-B, sterile insect technique.

Upscaling the production of sterile male mosquitoes with an automated pupa sex sorter.

Effective mosquito population suppression has been repeatedly demonstrated in field trials through the release of male mosquitoes to induce sterile mating with wild females using the incompatible insect technique (IIT), the sterile insect technique (SIT), or their combination. However, upscaling these techniques requires a highly efficient and scalable approach for the sex separation of mass-reared mosquitoes to minimize the unintentional release of females, which can lead to either population replacement or biting nuisance, a major bottleneck up to now. Here, we report the successful development of an automated mosquito pupa sex sorter that can effectively separate large numbers of males from females for population suppression of Aedes aegypti, A. albopictus, and Culex quinquefasciatus. The male production capacity of the automated sex sorter was increased by ~17-fold compared with manual sex separation with the Fay-Morlan sorter and enabled one person to separate 16 million males per week. With ~0.5% female contamination, the produced males exhibited high flight ability and mating performance. The field trial demonstrates that the quality of A. albopictus males produced using the automated sex sorter is suitable for inducing population suppression. These results indicate that the automated sex sorter offers the potential to upscale IIT and SIT against mosquito vectors for disease control.

Gene drives: an alternative approach to malaria control?

Genetic modification for the control of mosquitoes is frequently touted as a solution for a variety of vector-borne diseases. There has been some success using non-insecticidal methods like sterile or incompatible insect techniques to control arbovirus diseases. However, control by genetic modifications to reduce mosquito populations or create mosquitoes that are refractory to infection with pathogens are less developed. The advent of CRISPR-Cas9-mediated gene drives may advance this mechanism of control. In this review, use and progress of gene drives for vector control, particularly for malaria, is discussed. A brief history of population suppression and replacement gene drives in mosquitoes, rapid advancement of the field over the last decade and how genetic modification fits into the current scope of vector control are described. Mechanisms of alternative vector control by genetic modification to modulate mosquitoes' immune responses and anti-parasite effector molecules as part of a combinational strategy to combat malaria are considered. Finally, the limitations and ethics of using gene drives for mosquito control are discussed.

Ultrastructure of the Spermiogenesis in Halyomorpha halys (Hemiptera: Pentatomidae): X-Irradiation and New Insights on the Centriolar Region Organization.

Halyomorpha halys (Heteroptera: Pentatomidae) is an insect pest native to Asia that has spread over the last two decades to most of the North America, parts of South America, Europe and North Africa. Its impact is significant as it can feed on more than 300 host plants, rendering affected fruits and vegetable crops unsellable or of lower quality. Various chemical and biological methods have been used to control this pest, with varying degrees of success. The sterile insect technique (SIT) is a pest control method involving the sterilization of insects via ionizing radiation and their subsequent mass release into the field. In the present contribution, the spermiogenesis of H. halys was studied from an ultrastructural point of view in both irradiated and non-irradiated adult males. In both cases, we observed ultrastructural characteristics typical of hemipteran sperm cells: bridges connecting the mitochondrial derivatives and the axonemal microtubules, the absence of accessory bodies, and the presence of two or three crystalline inclusions within the mitochondrial derivatives, an acrosome composed of tightly packed tubules, and an atypical, plaque-shaped microtubular organizing center (MTOC) in the centriolar region. Moreover, in the same region, we seldom observed the presence of two centrioles in the spermatids, one of which disappeared at a later stage of maturation. This feature is a novelty for insect spermiogenesis. The cysts of irradiated adults were not all uniformly affected by the radiation. However, irradiated cysts sometimes exhibited a general disorganization of sperm arrangement, incomplete divisions of sperm cells resulting in multiple copies of the same organelle within the same cell, failure to reabsorb the cytoplasm, and the lack of axonemes. Finally, rod-shaped viruses or virus-like particles were observed in vasa deferentia independently of irradiation.

Radioactivity and GMO-Free Sterile Insect Technology for the Sustainable Control of the Invasive Pest Drosophila suzukii.

Drosophila suzukii (D. suzukii), commonly known as the spotted wing drosophila, is a highly invasive crop pest that is difficult to control using chemical insecticides. To address the urgent need for alternative and more sustainable control strategies, the sterile insect technique (SIT) is improved, which involves the release of sterilized male insects to mate with fertile conspecifics, thereby reducing the size of the pest population in the subsequent generation. The three critical aspects that influence the success of SIT programs in D. suzukii are addressed. First, an accurate and nondestructive method is established to determine the sex of individual insects based on the differential weight of male and female pupae. Second, conditions for X-ray sterilization are systematically tested and an optimal dose (90kV/40Gy) is identified that ensures the efficient production of sterile D. suzukii for release. Finally, the inherent thermosensitivity of D. suzukii males is exploited to develop a temperature-based sterilization technique, offering an alternative or additional SIT method for this pest. These advances will contribute to the development of a comprehensive and effective strategy for the management of D. suzukii populations, reducing their impact on agriculture and helping to safeguard crop yields.

Eliminating malaria vectors with precision-guided sterile males

Controlling the principal African malaria vector, the mosquito Anopheles gambiae, is considered essential to curtail malaria transmission. However, existing vector control technologies rely on insecticides, which are becoming increasingly ineffective. Sterile insect technique (SIT) is a powerful suppression approach that has successfully eradicated a number of insect pests, yet the A. gambiae toolkit lacks the requisite technologies for its implementation. SIT relies on iterative mass releases of nonbiting, nondriving, sterile males which seek out and mate with monandrous wild females. Once mated, females are permanently sterilized due to mating-induced refractoriness, which results in population suppression of the subsequent generation. However, sterilization by traditional methods renders males unfit, making the creation of precise genetic sterilization methods imperative. Here, we introduce a vector control technology termed precision-guided sterile insect technique (pgSIT), in A. gambiae for inducible, programmed male sterilization and female elimination for wide-scale use in SIT campaigns. Using a binary CRISPR strategy, we cross separate engineered Cas9 and gRNA strains to disrupt male-fertility and female-essential genes, yielding >99.5% male sterility and >99.9% female lethality in hybrid progeny. We demonstrate that these genetically sterilized males have good longevity, are able to induce sustained population suppression in cage trials, and are predicted to eliminate wild A. gambiae populations using mathematical models, making them ideal candidates for release. This work provides a valuable addition to the malaria genetic biocontrol toolkit, enabling scalable SIT-like confinable, species-specific, and safe suppression in the species.

Exploration of the potential of a boosted sterile insect technique to control fruit flies in mango orchards

AbstractBACKGROUNDAn innovative version of the sterile insect technique (SIT) for pest control, called boosted SIT, relies on the use of sterile males coated with a biocide to control a target wild pest population of the same species. The objective of the present study was to assess the relevance of such technology to control the fruit fly Bactrocera dorsalis and fruit losses in mango orchards using. An agent‐based simulation model named BOOSTIT was used to explore the reduction of fruit losses thank to sterile male fruit flies control and economic benefits according to different strategies of sterile male release. The simulation considered a landscape of 30.25 ha made up of four mango orchards.RESULTSThe SIT and the boosted SIT reduced fruit losses when releases were made before the mango fruiting period. According to model simulations, releases should be performed at least seven times at 2‐week intervals and with a sterile/wild male ratio of at least 10:1. Considering the benefit/cost ratio (BCR), few releases should be done with a late start date. The BCR showed economic gains from the two control methods, the number of saved fruits and BCR being higher for SIT.CONCLUSIONOur simulations showed that SIT would have better results than the boosted SIT to contribute to an effective control of Bactrocera dorsalis at the scale of a small landscape. We highlight the need for laboratory studies of other types of pathogen to find a suitable one with higher incubation time and lower cost. © 2024 Society of Chemical Industry.

Mark-Release-Recapture (MRR) of Sterile Male Aedes albopictus (Skuse) in Sri Lanka: Field Performance of Sterile Males and Estimation of the Wild Mosquito Population Density.

Dengue is an important mosquito-borne disease in Sri Lanka. The Sterile Insect Technique (SIT) is an environment-friendly and novel method that can suppress dengue vector mosquitoes in Sri Lanka. This study aimed to evaluate the field performance of sterile males and the density of wild male Aedes albopictus (Skuse) using a Mark-Release-Recapture (MRR) assay. Laboratory-colonized male pupae were exposed to 50 Gy gamma using a Co60 source. Sterile males (approx. 10,000) marked with fluorescent dust were released weekly for 4 consecutive weeks (January-February 2021) in a geographically isolated 30 ha site in Gampaha. Results show sterile males could disperse up to 543.8 m with a mean distance of 255.1 ± 44.6 m and survive up to 6 days with a mean life expectancy of 3.55 ± 2.32 days. A high field mating competitiveness of sterile males based on a Fried value of 0.47 ± 0.007 and significant induced sterility in the wild eggs in the second generation were found. The mean wild male mosquito population density was 163 males/ha. The data generated will be useful for designing future trials in Sri Lanka and other countries with similar situations.

Pink Bollworm management in cotton: Challenges, innovations, and sustainable solutions

Pink bollworm (Pectinophora gossypiella) poses a significant threat to cotton production worldwide. Despite the initial success of Bt cotton, resistance has emerged, necessitating alternative management strategies. Integrated Pest Management (IPM) approaches, including mating disruption and the sterile insect technique (SIT), offer promising solutions. The SPLAT (Specialized Pheromone and Lure Application Technology) technique utilizes wax-based formulations to disrupt pink bollworm mating behaviour, reducing population growth and damage to cotton crops. Meanwhile, SIT utilizes radiation to induce sterility in pink bollworm populations, reducing reproductive rates and mitigating infestation levels. Embracing these innovative strategies collectively ensures sustainable cotton cultivation, safeguarding farmers' livelihoods and reinforcing resilience against the persistent threat of the pink bollworm. Keywords: Pectinophora gossypiella, Cotton, IPM, SPLAT, STI

Molecular epidemiology of the Old World screwworm fly (OWSF) in Iraq, and the genetic structure of various OWSF populations worldwide

Despite being endemic in Iraq, no reports have been published in the past 10 years to update the molecular epidemiology of the Old World screwworm fly (OWSF), Chrysomya bezziana, in this country. In the present study, 130 sheep from 10 Iraqi governorates were found infected with C. bezziana larvae, whose identities were PCR-confirmed based on the cytochrome b (Cytb) gene, and 23 isolates from various tested governorates were successfully sequenced. Although most isolates (n = 20) belonged to the common haplotype circulating in Iraq, two new haplotypes were detected. Significant changes in OWSF epidemiology in Iraq were also suggested, since infestations were detected, for the first time, in Nineveh governorate. Isolates of the present study were combined to those previously published from Iraq and worldwide, collected after searching the GenBank, and various genetic and population structure analyses were conducted. These isolates displayed a great statistically significant value when tested for the purifying (negative) selection, suggesting the limited occurrence of genetic variations, which was evidenced by the high sequence conservation (C = 0.937) value detected. A few isolates from Africa were revealed during our search, and clustered in a separate lineage other than that of the Asian isolates. The latter displayed different genetic variation patterns when compared. For example, isolates from geographically separate regions, e.g., the Gulf Arab countries and South-Eastern Asia had marked genetic differences. On the other hand, isolates from regions with close geographic proximity (the Gulf Arab countries and Iran) had limited genetic subdivision. This is not the case when comparing isolates from 10 islands in the Indonesian Archipelago. Populations from Sumatra and Sumba were isolated and displayed high genetic variations toward the other populations. On the contrary, populations from Sulawesi, Lombok and Sumbawa displayed limited genetic variations. This is particularly important, since it can help detecting the dynamics of establishing the sterile insect technique over various regions as an effective control strategy against the OWSFs.

Potential shortfalls of using entomopathogenic fungi for boosting the sterile insect technique to control the oriental fruit fly, Bactrocera dorsalis

Potential shortfalls of using entomopathogenic fungi for boosting the sterile insect technique to control the oriental fruit fly, Bactrocera dorsalis

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

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 130ml of water and with a dose of 40Gy 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 Techniqueprogram to control Ae. albopictus on Reunion Island, which required the production of more than 300,000 sterile males per week.