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Top left: the green dots and letters indicate the position of the three localities within the PoÕ Valley (EmiliaRomagna region, Northern Italy). Top right and bottom: maps of Castel Maggiore (a), Altedo (b), and Castello dÕArgile (c), showing the sites where marked Ae. albopictus males were released and the sites where swarming and human landing Ae. albopictus males were collected during the three recapture sessions (4, 5, and 7 d after release). Yellow dots indicate the swarming malesÕ capture points; red points indicate the human landing malesÕ capture points. In case of superimposition, dots position was slightly changed to make all sampling points visible on the maps. (Online Þgure in color.).
Source publication
The dispersal and survival of laboratory-reared Aedes albopictus Skuse males were investigated during the summer of 2007 in three Northern Italy urban localities by mark-release-recapture techniques. Two marking methods were compared: one group of males was dusted with fluorescent pigments on the body (FP), and the other group was obtained from a s...
Contexts in source publication
Context 1
... Area. Mark-release-recapture experiments were conducted in three urban localities, all situated in the Po plain (Northern Italy, Bologna province; Fig. 1): Castel Maggiore (4434 40ÕN, 1121 42ÕE), with 13,769 inhabitants and an average density of 6,551 inhabitants/km 2 and 1,222 houses within an area of 2.1 km 2 ; Altedo (4440 4ÕN, 1129 30ÕE), with 3,512 inhabitants, an average density of 2,319 inhabitants/ km 2 , and encompassed 1,090 houses on an area of 1.5 km 2 ; and Castello ...
Context 2
... awareness of the private residents. The campaigns for community involvement, even when regularly conducted with professional methods, rarely achieve a level of active participation that can be considered sufÞcient for an adequate sustainment of the mosquito control programs (Morrison et al. 2008). At the same time, the demand to implement the use of adulticide treatments in private and in public areas is increasing, with negative environmental and sanitary side effects as a result of exposure to toxic products. Starting from the scenario described above, a research project for the development of a sterile insect technique (SIT) program for the suppression of Ae. albopictus in Italy started in 1999 (Bellini et al. 2007). The SIT strategy consists of mass rearing, sterilization, and repeated release of sterile insects, to progressively reduce the reproductive rate of the target species (Alphey et al. 2010). In the case of mosquito species, it is necessary to release only males, as the release of biting females is not acceptable. Some biological and ecological features make Ae. albopictus a good candidate for the application of SIT. Mass rearing of Aedes species is relatively easy when compared with other mosquito species ( Anopheles ), and a pilot model system to rear Ae. albopictus has already been set up at our facility in Crevalcore, Italy (Bellini et al. 2007). The genetic differentiation observed among the Italian populations showed at the regional geographic scale the existence of structured populations with restricted gene exchange among them (Urbanelli et al. 2000); the active dispersal of the species is recognized to be poor (Hawley 1988, Rai 1991, Niebylski and Craig 1994, Takagi et al. 1995, Hono ́ rio et al. 2003). Knowledge about male survival and dispersal capacity in the Þeld is of fundamental importance to develop SIT programs. Being hematophagous, the vector, mark-release-recapture experiments have been used largely to study mosquito female dispersal and survival in different ecological conditions (Bonnet and Worcester 1946, Mori 1979, Niebylski and Craig 1994, Takagi et al. 1995, Lacroix et al. 2007). On the contrary, very few studies were targeted on mosquito males (Ferguson et al. 2005), and little information is available on male biology, ecology, and behavior (Trips and Hauserman 1986, Niebylski and Craig 1994, Muir and Kay 1998, Lacroix et al. 2007). Our study was designed to investigate, through mark-release-recapture trials, the dispersal pattern and survival in urban areas of Ae. albopictus males. Two methods were used to mark the reared males before the release. The Þrst one involved the use of ßuorescent pigments, and was already applied by several authors to a number of mosquito species in different habitats and with different dispersal behavior (Service 1997, Vlach et al. 2006, Bogojevic ́ et al. 2007). The second marking method involved the use of an aposymbiotic strain, whose Wolbachia infection had been removed. To our knowledge, this is the Þrst time this approach has been used in mark- recapture-release trials. Wolbachia are maternally transmitted ricksettsia-like bacteria, estimated to infect as many as 16 Ð22% of all insects (Werren et al. 1995, West et al. 1998, Werren and Windsor 2000). Ae. albopictus is reported to be uniformly superinfected with two Wolbachia strains ( w Alb A and w Alb B) throughout its geographical area of distribution, and the occurrence of noninfected males has never been reported (Zhou et al. 1998; Dobson et al. 2001; M.C., unpublished data). Apo- symbiotic strains may be produced by providing adult mosquitoes with tetracycline, according to the protocol of Dobson and Rattanadechakul (2001). Previous research found that uninfected females, obtained with the antibiotic treatment, showed a decrease in their Þtness, compared with females normally infected with Wolbachia (Dobson et al. 2004). In contrast, no difference was observed in longevity and mating parameters of uninfected males in comparison with the natural infected ones (Calvitti et al. 2009). Consequently, we assumed as feasible the use of an aposymbiotic strain for mark- release-recapture studies, focused on Ae. albopictus males. The release of Wolbachia -free Ae. albopictus males does not pose any environmental risk, because the aposymbiotic status can be only maternally inherited to progeny. Study Area. Mark-release-recapture experiments were conducted in three urban localities, all situated in the Po plain (Northern Italy, Bologna province; Fig. 1): Castel Maggiore (44 Њ 34 Ј 40 Ј ÕN, 11 Њ 21 Ј 42 Ј ÕE), with 13,769 inhabitants and an average density of 6,551 inhabitants/km 2 and 1,222 houses within an area of 2.1 km 2 ; Altedo (44 Њ 40 Ј 4 Ј ÕN, 11 Њ 29 Ј 30 Ј ÕE), with 3,512 inhabitants, an average density of 2,319 inhabitants/ km 2 , and encompassed 1,090 houses on an area of 1.5 km 2 ; and Castello dÕArgile (44 Њ 40 Ј 52 Ј Õ, 11 Њ 17 Ј 48 Ј ÕE), with a population of ϳ 2,964 inhabitants, an average density of 2,298 inhabitants/km 2 , and encompassed 709 houses on an area of nearly 1 km 2 . The percentages of land covered by vegetation within a radius of 350 m from the center of the investigation areas were 37% for Castel Maggiore, 37% for Altedo, and 46% for Castello dÕArgile. Each locality was surrounded by rural areas and included usually two-storied houses, sepa- rated by narrow lanes, with many private and some public gardens. These landscape features are repre- sentative of most of the small towns in Northern Italy. The presence of Ae. albopictus populations in these areas had been proven by monitoring activities conducted since 2003 (R.B., unpublished data). Mosquito Rearing and Marking Procedure. All released males were obtained from the mass rearing pilot system of the Laboratory of the Medical and Veteri- nary Department of the Environmental and Agricul- ture Centre “ G. Nicoli ” in Crevalcore (Bologna, Italy). Standard rearing conditions were 27 Ϯ 1 Њ C, 85% RH, 15- to 9-h light-dark photoperiod. Adults were kept in Plexiglas cages (50 ϫ 50 ϫ 50 cm) supplied with a 10% sucrose solution. Females were blood fed with fresh mechanically deÞbrinated bovine blood, by means ...
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Background:
Mass egg production is an important component of Aedes albopictus mosquito control programs, such as the sterile insect technique and incompatible insect technique, which requires the releases of large number of sterile males. Developing standard operating procedures and optimized cages for adult maintenance of Ae. albopictus can impro...
Mosquito-borne diseases represent a major threat to humankind. Recently, the incidence of malaria has stopped decreasing while that of dengue is increasing exponentially. Alternative mosquito-control methods are urgently needed. The sterile insect technique (SIT) has seen significant developments recently and may play an important role. However, te...
Citations
... Many studies suggest that wild Ae. albopictus are short-dispersing mosquitoes, generally moving fewer than a few hundred meters [28,[51][52][53], which is in line with our results on sterile male dispersal under field conditions. Further, the recapture rate strongly depends on the dispersal capacity of the target species, on the recapture effort (density of recapture stations), and on the efficacy of the recapture method employed [54]. ...
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.
... In addition, the production capacity of sterile males increased due to the introduction of improvements in rearing processes and staff training, and up to 42% more males per hectare were released compared to the first season. In relation to release frequency, studies to date have released sterile males from one to three times per week [12,13,28]. The average lifespan of sterile males in the field fluctuates greatly in temperate regions, where summer months reach high temperatures and low humidity rates. ...
... In a recent review, Moore established that the average estimated distance traveled by Ae. aegypti mosquitoes between the release site and the recapture location was 106 m [32]. In reference to Ae. albopictus, the existing literature refers to a similar average dispersion, although these data are usually referred to as Mark-Release-Recapture (MRR) tests, which usually involve only laboratory-reared males [28,33]. However, studies conducted with wild populations of both males and females have reported mean mosquito travel distances exceeding 300 to 600 m [29,34]. ...
Simple Summary
The tiger mosquito, Aedes albopictus (Skuse, 1894), is a competent vector of arboviruses such as dengue, Zika, and chikungunya among others. The sterile insect technique (SIT) is presented as an innovative and environmentally friendly control method to be implemented as a main component of integrated vector control management (IVM). In the Valencian region (Spain), an IVM pilot project led and funded by the Department of Agriculture, based on the use of SIT to control Ae. albopictus, has been carried out from 2017 to 2020. It has proven to be effective in reducing tiger mosquito populations. This manuscript analyzes the impact of the migration of wild individuals from peri-urban areas into non-isolated urban centers on the control strategy.
Abstract
In recent years, Aedes albopictus (Skuse, 1984) has expanded its distribution globally due to its high ecological plasticity. This expansion has increased the population’s susceptibility to contracting diseases such as dengue, Zika, and chikungunya, among others, which are transmitted by this mosquito species. In the absence of effective control methods, the application of the sterile insect technique (SIT) is proposed as part of an integrated vector management (IVM) program. From 2007 to 2020, this strategy has been tested in a non-isolated mosquito population urban area of 45 ha, representative of the municipalities of the Valencian region (Spain). The population levels of adult females and eggs collected in the traps have been reduced by 70–80% compared to the control area, demonstrating its efficacy in reducing mosquito populations. This work analyzes the impact of the migration of the wild mosquito population from the peri-urban area to the urban core.
... A robust method to distinguish sterile from fertile males is required prior to and during the release of sterile male mosquitoes. [11][12][13] The concept of using Wolbachia-free Ae. albopictus to distinguish sterile males from wild mosquitoes is not new, 34,57 but no relevant study has further tested this concept and its application feasibility in the frame of SIT. In this study, the fitness costs, radiosensitivity and arbovirus susceptibility of the GT strain were evaluated and found to be comparable to those of the wild GUA strain under laboratory conditions and our results suggest that it is feasible to use GT strain to control the Ae. ...
BACKGROUND
The sterile insect technique (SIT) is a green and species‐specific insect pest control technique that suppresses target populations by releasing factory‐reared, radiosterilized males into the wild. Once released, it is important to be able to distinguish the released males from the wild males for monitoring purposes. Several methods to mark the sterile males exist. However, most have limitations due to monetary, process efficiency, or insect quality. Aedes albopictus is naturally infected with Wolbachia at a high prevalence, therefore the elimination of Wolbachia can serve as a biomarker to distinguish factory‐reared male mosquitoes from wild conspecifics.
RESULTS
In this study, a Wolbachia‐free Ae. albopictus GT strain was developed and its fitness evaluated, which was found to be comparable to the wild GUA strain. In addition, GT male mosquitoes were irradiated at the adult stage and a dose of 20 Gy or more induced over 99% sterility. Moreover, a dose of 30 Gy (almost completely sterilizing male and female mosquitoes) had limited effects on the mating competitiveness of GT males and the vector competence of GT females, respectively. However, radiation reduced mosquito longevity, regardless of sex.
CONCLUSION
Our results indicate that the Ae. albopictus GT strain can be distinguished from wild mosquitoes based on Wolbachia status and shows similar fitness, radio‐sensitivity and arbovirus susceptibility to the GUA strain, indicating that it is feasible to use the GT strain to suppress Ae. albopictus populations for SIT programmes. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
... Notably, the estimate of the incompatible:sterile wild male ratio was very straightforward thanks to an effective male marking system stable throughout the whole male life: the wPip Wolbachiaspecific PCR-assay. 28,36 This represents an asset of IIT in comparison to SIT trials in the field, as the latter requires marking of irradiated male releases with fluorescent dusts, which progressively lose detectability over time and can be passed to other males during fights. 37 In order to evaluate the potential efficacy and sustainability of ARwP male release as a potential control strategy, we estimated the per-male efficiency associated to the incompatible strain, by taking into account not only the incompatible:wild male ratio, but also male survival. ...
BACKGROUND
Incompatible insect technique (IIT) is a population suppression approach based on the release of males with manipulated Wolbachia infection inducing egg inviability in wild females. We here present results of multiple field releases of incompatible ARwP males carried out in 2019 in a 2.7‐ha green area within urban Rome (Italy) to assess the effect on Aedes albopictus egg viability. Data are compared with results obtained in 2018, when the approach was tested for the first time in Europe.
RESULTS
An average of 4674 ARwP males were released weekly for 7 weeks, resulting in a mean ARwP:wild male ratio of 1.1:1 (versus 0.7:1 in 2018). Egg‐viability dynamics in ovitraps significantly varied between treated and control sites, with an estimated overall reduction of 35% (versus 15% in 2018). The estimated proportion of females classified as mated with ARwP males was 41.8% and the viability rate of eggs laid by these females (9.5%) was on average significantly lower than that of females only mated with wild males (87.8%); however, high variability in fertility was observed. Values of ARwP male competitiveness were 0.36 and 0.73 based on the overall viability rate of eggs in ovitraps and on female fertility, respectively; thus, well above the conventional 0.2 threshold for an effective suppressive impact in the field.
CONCLUSIONS
Results further support the potential of IIT as a tool to contribute to Ae. albopictus control in the urban context, stressing the need for larger field trials to evaluate the cost‐efficacy of the approach in temperate regions. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
... Marking using fluorescent powders is a common technique for externally marking adult mosquitoes [18][19][20][21]. This is to help assess multiple biological parameters, including population size, dispersal, mating and survival [22][23][24][25][26]. However, the interactions between the shipping/transportation, chilling and marking of sterile male mosquitoes has not yet been documented. ...
Pilot programs of the sterile insect technique (SIT) against Aedes aegypti may rely on importing significant and consistent numbers of high-quality sterile males from a distant mass rearing factory. As such, long-distance mass transport of sterile males may contribute to meet this requirement if their survival and quality are not compromised. This study therefore aimed to develop and assess a novel method for long-distance shipments of sterile male mosquitoes from the laboratory to the field. Different types of mosquito compaction boxes in addition to a simulation of the transport of marked and unmarked sterile males were assessed in terms of survival rates/recovery rates, flight ability and morphological damage to the mosquitoes. The novel mass transport protocol allowed long-distance shipments of sterile male mosquitoes for up to four days with a nonsignificant impact on survival (>90% for 48 h of transport and between 50 and 70% for 96 h depending on the type of mosquito compaction box), flight ability, and damage. In addition, a one-day recovery period for transported mosquitoes post-transport increased the escaping ability of sterile males by more than 20%. This novel system for the long-distance mass transport of mosquitoes may therefore be used to ship sterile males worldwide for journeys of two to four days. This study demonstrated that the protocol can be used for the standard mass transport of marked or unmarked chilled Aedes mosquitoes required for the SIT or other related genetic control programs.
... Understanding the bio-ecological features of the target population and how laboratory-produced sterile males may perform in the natural environment is crucial. Mark-releaserecapture (MRR) studies are particularly useful and have been frequently applied to various insect species to study characteristics of populations related to the ecology, biology, behavior, ability to transmit pathogens, and ultimately their control (Gillies, 1961;Pollock, 1991;Hagler and Jackson, 2001;Silver, 2007;Bellini et al., 2010;Epopa et al., 2017;Benedict et al., 2018;Oliva et al., 2021). Knowledge of the characteristics of sterile males and reliable quantification of wild population density are prerequisites for planning SIT interventions (Bouyer et al., 2020b;Romeis et al., 2020;Oliva et al., 2021). ...
... Two (series) sessions of MRR were performed with similar recapture rates for both BGS and HLC methods (3.93%) over 2 weeks in which the majority of males were caught within 5 days postrelease. This result is consistent with the literature (Bellini et al., 2010) or showed higher recapture rates than in the study by Iyaloo et al. (2020) who found recapture rates in Ae. albopictus ranging from 0.8% to 1.3% over 6 days post release and the study by Caputo et al. (2021) that found a recapture rate of 1.8% in the first 6 days. Winskill et al. (2015) found a recapture rate of 0.36% for another genetic control method based on the release of insects carrying a dominant lethal gene (RIDL). ...
The pathogen transmitting Aedes albopictus mosquito is spreading rapidly in Europe, putting millions of humans and animals at risk. This species is well-established in Albania since its first detection in 1979. The sterile insect technique (SIT) is increasingly gaining momentum worldwide as a component of area-wide-integrated pest management. However, estimating how the sterile males will perform in the field and the size of target populations is crucial for better decision-making, designing and elaborating appropriate SIT pilot trials, and subsequent large-scale release strategies. A mark-release-recapture (MRR) experiment was carried out in Albania within a highly urbanized area in the city of Tirana. The radio-sterilized adults of Ae. albopictus Albania strain males were transported by plane from Centro Agricoltura Ambiente (CAA) mass-production facility (Bologna, Italy), where they were reared. In Albania, sterile males were sugar-fed, marked with fluorescent powder, and released. The aim of this study was to estimate, under field conditions, their dispersal capacity, probability of daily survival and competitiveness, and the size of the target population. In addition, two adult mosquito collection methods were also evaluated: BG-Sentinel traps baited with BG-Lure and CO2, (BGS) versus human landing catch (HLC). The overall recapture rates did not differ significantly between the two methods (2.36% and 1.57% of the total male released were recaptured respectively by BGS and HLC), suggesting a similar trapping efficiency under these conditions. Sterile males traveled a mean distance of 93.85 ± 42.58 m and dispersed up to 258 m. Moreover, they were observed living in the field up to 15 days after release with an average life expectancy of 4.26 ± 0.80 days. Whether mosquitoes were marked with green, blue, yellow, or pink, released at 3.00 p.m. or 6.00 p.m., there was no significant difference in the recapture, dispersal, and survival rates in the field. The Fried competitiveness index was estimated at 0.28. This mark-release-recapture study provided important data for better decision-making and planning before moving to pilot SIT trials in Albania. Moreover, it also showed that both BG-traps and HLC were successful in monitoring adult mosquitoes and provided similar estimations of the main entomological parameters needed.
... Important factors that impact the quality of male mosquitoes such as flight performance can only be assessed by time-consuming methods such as male mating competitiveness assay in the laboratory and mark-release-recapture (MRR) in the field. In addition, MRR experiments provide low recapture rates (Bellini et al., 2010;Iyaloo et al., 2020) and are tedious and costly, while conventional mating competitiveness assay is not only laborious but time-consuming. To circumvent these difficulties, a quick, easy-toperform, and reliable quality control (QC) method to use before adult mosquitoes are released would be highly beneficial. ...
Successful implementation of the sterile insect technique (SIT) against Aedes aegypti and Aedes albopictus relies on maintaining a consistent release of high-quality sterile males. Affordable, rapid, practical quality control tools based on the male’s flight ability (ability to escape from a flight device) may contribute to meeting this requirement. Therefore, this study aims to standardize the use of the original FAO/IAEA rapid quality control flight test device (FTD) (version 1.0), while improving handling conditions and reducing the device’s overall cost by assessing factors that could impact the subsequent flight ability of Aedes mosquitoes. The new FTD (version 1.1) is easier to use. The most important factors affecting escape rates were found to be tube color (or “shade”), the combined use of a lure and fan, mosquito species, and mosquito age and density (25; 50; 75; 100 males). Other factors measured but found to be less important were the duration of the test (30, 60, 90, 120 min), fan speed (normal 3000 rpm vs. high 6000 rpm), and mosquito strain origin. In addition, a cheaper version of the FTD (version 2.0) that holds eight individual tubes instead of 40 was designed and successfully validated against the new FTD (version 1.1). It was sensitive enough to distinguish between the effects of cold stress and high irradiation dose. Therefore, the eight-tube FTD may be used to assess Aedes’ flight ability. This study demonstrated that the new designs (versions 1.1 and 2.0) of the FTD could be used for standard routine quality assessments of Aedes mosquitoes required for an SIT and other male release-based programs.
... In addition to the maintenance of an effective vector competence, the irradiated females accidentally released during an SIT campaign must effectively disperse, feed, and survive in the field to increase the risk of transmission of arboviral diseases. The mean survival rates observed during mark-release-recapture studies with irradiated and unirradiated Aedes males were similar with a mean lifespan estimated at two to eleven days (Muir and Kay, 1998;Bellini et al., 2010;Brady et al., 2013;Vavassori et al., 2019). As the more radiosensitive female mosquitoes have shorter survival than their male counterparts under laboratory conditions (Bond et al., 2019;Aldridge et al., 2020), further investigations will be required to estimate if irradiated females are capable of surviving the EIP to become infectious under field conditions. ...
Effective control strategies against arthropod disease vectors are amongst the most powerful tools to prevent the spread of vector-borne diseases. The sterile insect technique (SIT) is an effective and sustainable autocidal control method that has recently shown effective population suppression against different Aedes vector species worldwide. The SIT approach for mosquito vectors requires the release of radio-sterilized male mosquitoes only, but currently available sex separation techniques cannot ensure the complete elimination of females resulting in short-term risk of increased biting rate and arboviral disease transmission. In this study, we compared for the first time the transmission of dengue and chikungunya viruses in Aedes aegypti and Aedes albopictus females exposed as pupae to an irradiation dose of 40 Gy. Females of both species were fed on blood spiked with either dengue or chikungunya viruses, and body parts were tested for virus presence by real-time RT-PCR at different time points. No differences were observed in the dissemination efficiency of the dengue virus in irradiated and unirradiated Ae. albopictus and Ae. aegypti mosquitoes. The dissemination of the chikungunya virus was higher in Ae. albopictus than in Ae. Aegypti, and irradiation increased the virus load in both species. However, we did not observe differences in the transmission efficiency for chikungunya (100%) and dengue (8–27%) between mosquito species, and irradiation did not impact transmissibility. Further implications of these results on the epidemiology of vector-borne diseases in the field are discussed.
... Quality control tests may include traits to assess proportion of emergence, flight ability, stress resistance, longevity and mating competitiveness with a goal to predict the performance of the sterile insects in the wild. The quality of the sterile mosquitoes can be assessed in laboratory, semi-field and field conditions [30,31]. Standard QC procedures in most advanced SIT programs include the insect's ability to fly out of simple tube devices [32][33][34][35]. ...
Genetic based mosquito control methods have been gaining ground in recent years for their potential to achieve effective suppression or replacement of vector populations without hampering environments or causing any public health risk. These methods require the mass rearing of the target species in large facilities sized to produce millions of sterile males, as already well established for a number of insects of agricultural importance. Assessing the performance of released males in Sterile Insect Technique (SIT) control programs is of the utmost importance for the success of the operation. Besides the negative effects of mass rearing and sterilization, the handling of sterilized insects and shipment to distant areas may also negatively impact the quality of sterilized males. The aim of the current study was to design and executive quality control (QC) tests for sterilized Aedes albopictus (Asian tiger mosquito) males delivered by air shipment from the mass production facility located in Italy to Greece and Montenegro field release sites. Mass reared mosquito strains were based on biological materials received from Italy, Greece and Montenegro. Tests conducted at the mass rearing facility before transportation revealed a rather high residual female contamination following mechanical sex separation (approximately 1.5% females, regardless of the mosquito strain). Irradiated males of all three mosquito strains induced high levels of sterility to females. Shipment lasting approximately 24 h resulted in approximately 15% mortality, while when shipment lasted nearly two days this increased to almost 40%. The flight ability of sterilized males following one day transportation time was satisfactory (over 60%). The response of sterile males to food and water starvation was comparable and slightly lower than that of wild non-transported males. Longevity of sterile males was shorter than that of wild counterparts and it seems it was not affected by mating to wild females. Both mating propensity and mating competitiveness for wild virgin females was higher for the wild, control males compared to the sterile, transported ones. Overall, the performance of sterile male Ae. albopictus delivered from the mass rearing facility of Italy to Greece in approximately 24 h was satisfactory. Transportation lasting two days or longer incurred detrimental effects on males, which called into question the outcome of the SIT release programs. In conclusion, our results demonstrate the need of quality control procedures, especially when sterile male production facilities are not near to the releasing point. Transportation could be a serious drawback for the implementation of Sterile Insect Releases and, consequently, it is important to establish an efficient and fast transportation of sterilized males in advance.
... However, models are now being developed to improve this estimation (Barclay et al., 2013). These models show that spatial heterogeneity (Ferreira et al., 2008) and dispersal behaviour (Bellini et al., 2010;Kura et al., 2019) are important parameters to include in models. Species bioecology, landscape characteristics and weather parameters influence trapping results and can affect model predictions. ...
Knowing the dispersal of released insects and estimating the size of field populations are keys to the successful implementation of area‐wide management (AWM) programmes based on the sterile insect technique (SIT), as they determine the release strategy of sterile males. Mark–release–recapture (MRR) is a common method used to estimate field populations and spatiotemporal dynamics. However, the extent to which the pest is attracted to lures is often difficult to identify, thereby biasing extrapolation to movement patterns and population size. We performed MRR experiments on the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), in a fruit‐growing area in Senegal. Methyl eugenol and protein baits were used to trap males and females, respectively. After studying the suitability of marking B. dorsalis with fluorescent pigments at the laboratory, two releases of marked sterile flies were organized in the centre of an organic mango orchard, first in the late mango fruiting stage and second in the fruit setting stage. Traps were placed symmetrically along a 250 and 500 m radius from the release point. A very small fraction of the released individuals was recaptured: 0.45% in the first release and 3.08% in the second. Trapping of both sterile and wild flies was completely anisotropic. Sterile flies were mostly trapped at a relatively short distance (250 m) from the release point, in the first two days. Male trapping using methyl eugenol was highly effective, whereas the response of females to food bait traps was low. The direction of the wind was the main driver of recapture, with flies heading upwind. The results underline the importance of taking the odour plume around the traps into account when estimating populations, and the heterogeneous spread of the wild population in the landscape for the set‐up of the release strategy of sterile insects for SIT‐based AWM.
