Sterile Insect Research Articles

EFFECT OF GAMMA IRRADIATION ON THE QUALITY AND MATING COMPETITIVENES OF FRUIT FLIES Bactrocera dorsalis IN THE CAGE SCALE

Bactrocera dorsalis is an important fruit fly attack fruits and vegetables in Indonesia. Sterile Insect Technique (SIT) is sterilize with gamma irradiation, released as many as 9 x wild population, ecpected to mate but didn’t produce offspring. The research porpuse was to determine the effect of gamma irradiation on the quality and on the mating competitiveness in cage scale. The experimental design was completely randomized design with one factor was gamma irradiation dosee at 6 levels were 0 (control), 30, 50, 70, 90 and 110 Gy as many as 4 replicates. The result that the level of the radiation dose had a significant on the competitiveness and quality included the percentage of pupae became adult adult, sex ratio, the percentage of fly ability, the number of eggs produced (fecundity) and percentage hatching eggs. The quality decreased when increasing in radiation dose. The dose level didn’t affect the fecundity but affected the mating competitiveness in cage scale. The value total of mating campetitivenes was highest at a dose of 70 Gy treatment were 0.76 (5:1:1) and 0.79 (10:1:1), followed by dose of 50 Gy were 0,41 (5:1:1) and 0,50 (10:1:1).

Development of genetic sexing strain of the oriental fruit fly, Bactrocera dorsalis (Hendel)

A genetic sexing strain (GSS) of the oriental fruit fly, Bactrocera dorsalis (Hendel) has been developed in order to release only sterile males to increase the efficiency of fruit fly control by using sterile insect technique. To compare the quality of GSS with the genetic marker strain from a mass-reared colony, it was found that eclosion, flight ability and fertility of GSS equal to 69.57, 53.14 and 47.48 % respectively, which were significantly lower than those of the genetic-marker strain. The adult eclosion, flight ability and fertility of the genetic-marker strain equal to 93.66, 87.00 and 60.48 % respectively. To study the effects of irradiation, the 2-days-before-emergence pupae of GSS were irradiated at doses of 70 and 90 Gy. It was found that sterility and competitiveness index of GSS irradiated at 70 and 90 Gy were 96.15, 97.12 % and 0.51, 0.39 respectively.

The chromosomes of Drosophila suzukii (Diptera: Drosophilidae): detailed photographic polytene chromosomal maps and in situ hybridization data

The spotted wing drosophila, D. suzukii, is a serious agricultural pest attacking a variety of soft fruits and vegetables. Although originating from East Asia it has recently invaded America and Europe raising major concern about its expansion potential and the consequent economic losses. Since cytogenetic information on the species is scarce, we report here the mitotic karyotype and detailed photographic maps of the salivary gland polytene chromosomes of D. suzukii. The mitotic metaphase complement contains three pairs of autosomes, one of which is dot-like, and one pair of heteromorphic (XX/XY) sex chromosomes. The salivary gland polytene complement consists of five long polytene arms, representing the two metacentric autosomes and the acrocentric X chromosome, and one very short polytene element, which corresponds to the dot-like autosome. Banding pattern as well as the most characteristic features and prominent landmarks of each polytene chromosome arm are presented and discussed. Furthermore, twelve gene markers have been mapped on the polytene chromosomes of D. suzukii by in situ hybridization. Their distribution pattern was found quite similar to that of D. melanogaster revealing conservation of synteny although the relative position within each chromosome arm for most of the genes differed significantly between D. suzukii and D. melanogaster. The chromosome information presented here is suitable for comparative cytogenetic studies and phylogenetic exploration, while it could also facilitate the assembly of the genome sequence and support the development of genetic tools for species-specific and environment-friendly biological control applications such as the sterile insect technique.

Comparison between pupal and adult X-ray radiation, designed for the sterile insect technique for Aedes albopictus control

Aedes albopictus is a vector of several human viral diseases, including dengue, chikungunya, and Zika. New control method for Aedes albopictus is needed to replace traditional methods such as chemical insecticides which induce resistance, environmental contamination and toxicity to human. In sterile insect technique (SIT), male mosquitoes are sterilized by γ-ray or X-ray irradiation before released. In this study, the relative effectiveness of X-ray irradiation as a mosquito SIT was investigated. Both pupal and adult Aedes albopictus were subjected to different radiation doses and their emergence, survivorship, longevity, induced sterility, and male mating competitiveness were evaluated. Relative to controls, irradiation had no significant effect on emergence and survivorship but significantly reduce adult longevity. Induced sterility were essentially same for both irradiated pupal and adult. At a dose of 40 Gy, 97% and 100% sterility was respectively achieved for males and females. Mating competitiveness was reduced both in adult males and those derived from pupae exposed to 40 Gy. However, populations can be suppressed by increasing the release ratio (sterile: normal). When the release ratio was 7:1, 74% of the wild population could be suppressed. Overall, the results of the present study showed that SIT based on X-Ray irradiation is scientific and feasible to control Aedes albopictus.

Mechanical sorting of young Anastrepha ludens Tapachula-7 pupae, a host for Coptera haywardi, negatively affects sterile male quality

The Genetic Sexing Strain (GSS) of Anastrepha ludens (Loew) Tapachula-7 (Tap-7) produces males emerged from brown pupa [used for the Sterile Insect Technique (SIT)] and females from black pupa (a by-product) that can be sorted by a mechanical process. The early sorting provides young black pupae which were assessed as host of the parasitoid Coptera haywardi (Oglobin). This required an assessment of possible deleterious effects to A. ludens males (that emerged from the brown pupae). Our results demonstrate the host viability of the young Tap-7 black pupae. Nevertheless, A. ludens males obtained from brown pupae showed significantly reduced emergence (77.28%) and flight ability (63.33%). This negatively affected the emission of male signals for mating and, therefore, the competitiveness of A. ludens GSS used for the SIT. Our results suggest that there is no immediate alternative to the use of Tap-7 young black pupae as hosts for the mass rearing of C. haywardi.

When Less Is More: Sex Ratios for the Mass-Rearing of Anastrepha ludens (Diptera: Tephritidae)

Anastrepha ludens (Loew) is one of the most important pests of citrus and mango crops in Mexico. A method used to control this pest is the sterile insect technique, which consists in the mass production, irradiation, and release of insects in affected areas. The production of insects begins with the establishment of colonies to produce eggs, which must be highly fertile to ensure an adequate production of larvae. However, female fecundity and fertility can be affected by adult density and sex ratio, thus an optimal sex ratio in mass-rearing cages must be used. The genetic sexing strain of A. ludens (Tapachula-7) allows the identification of the sex at the pupal stage, making it possible to establish rearing cages with different sex ratios. We determined if different sex ratios have an effect on egg production. Two sex ratios (4♀: 1♂ and 1♀: 1♂) were compared. Fecundity, fertility and survival at different ages were also determined. Higher fertility and fecundity per female were observed at a ratio of 4:1. However, females with higher fecundity had reduced survival probabilities. In conclusion, maintaining colonies with a lower proportion of males in cages ensures a greater fecundity and fertility. Further research is necessary to understand whether results can be attributed to lower male harassment in cages.

Effects of experimental warming on wild and transgenic oriental fruit fly, Bactrocera dorsalis

AbstractClimate change may influence the application efficiency of transgenic marking, such as in mark–release–recapture (MRR) experiments or sterile insect technique (SIT). Wild and transgenic fruit flies of Bactrocera dorsalis were subjected to oscillating regimes that represent current temperature conditions (mean: 28.6°C) and various future possible scenarios (means: 30.0, 32.5 and 35.0°C). As the temperature was increased to 30.0°C, the negative effects on adult fecundity and demographic parameters (net reproductive rate and intrinsic rate of increase) of only the transgenic cohorts increased. With a moderate warming (32.5°C), negative effects were observed on the net reproductive rate for both fly strains, and these effects on the life‐history traits (adult fecundity and longevity) and intrinsic rate of increase were stronger in the transgenic than in the wild cohorts, with reference to the trait values at 30.0°C. A severe warming (35.0°C) resulted in the failure of all individuals of both fly strains to reach adulthood. We suggest parametrical adjustments or decreased differences in fitness with refined transgenesis under current and future climate conditions, which can reduce the marking limitations of pest management and eradication programmes.

Tephritidae bacterial symbionts: potentials for pest management.

Tephritidae is a large family that includes several fruit and vegetable pests. These organisms usually harbor a variegated bacterial community in their digestive systems. Symbiotic associations of bacteria and fruit flies have been well-studied in the genera Anastrepha, Bactrocera, Ceratitis, and Rhagoletis. Molecular and culture-based techniques indicate that many genera of the Enterobacteriaceae family, especially the genera of Klebsiella, Enterobacter, Pectobacterium, Citrobacter, Erwinia, and Providencia constitute the most prevalent populations in the gut of fruit flies. The function of symbiotic bacteria provides a promising strategy for the biological control of insect pests. Gut bacteria can be used for controlling fruit fly through many ways, including attracting as odors, enhancing the success of sterile insect technique, declining the pesticide resistance, mass rearing of parasitoids and so on. New technology and recent research improved our knowledge of the gut bacteria diversity and function, which increased their potential for pest management. In this review, we discussed the diversity of bacteria in the economically important fruit fly and the use of these bacteria for controlling fruit fly populations. All the information is important for strengthening the future research of new strategies developed for insect pest control by the understanding of symbiotic relationships and multitrophic interactions between host plant and insects.

The use of transgenic mosquitoes for prevention of spread of arboviral diseases.

The mosquitoes of Aedes genus are the most important vector such arboviral diseases as dengue, yellow, Chikungunya, West Nile and Zika fevers. Work is currently in progress to control the transmission of agents of these diseases by forming of transgenic mosquitoes in order to altering the capacity of wild mosquitoes to support of virus replication. There are two main strategies of genetic control of mosquitoes population. Sterile Insect Technique (SIT), that mainly uses population suppression methods for making self-sustaining genetic systems and Release of insects carrying of a Dominant Lethal (RIDL) that uses mainly gene transfer methods for making of self-limiting genetic systems. The RIDL is more expensive, but it has some significant preferences, according compares with SIT. The field trials of genetic control methods are conducted in several countries from 2009 to present time. Genetic control, transgenic technologies to induce sterility, genetic elimination and stable transformation of Aedes mosquitoes are viewed in this review.

Assessment of Olfactory Responses of Bactrocera zonata, B. cucurbitae and B. Dorsalis (Diptera: Tephritidae) to different biolure baits and Combined Use of Male Annihilation Technique (MAT) and sterile insect technique (SIT) in IPM programme for Bactorecera Fruit Flies

Assessment of Olfactory Responses of Bactrocera zonata, B. cucurbitae and B. Dorsalis (Diptera: Tephritidae) to different biolure baits and Combined Use of Male Annihilation Technique (MAT) and sterile insect technique (SIT) in IPM programme for Bactorecera Fruit Flies

Effect of natural predators on Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) control by sterile insect technique (SIT).

Queensland fruit fly (Q-fly) is a destructive insect pest that infests a wide variety of agricultural plants in Australia. The sterile insect technique (SIT) is used to manage Q-flies, but the effectiveness of SIT has not been tested in the presence of natural predators. The objective of this study was to investigate the effect of natural predators and SIT on the survival and reproduction of laboratory reared Q-flies under semi-natural conditions. We altered the presence of predators and irradiated Q-fly males, and measured survival, number of eggs laid and egg-hatching rate. The presence of natural predators significantly affected the survival of Q-flies and appeared to decrease the number of eggs laid. Interestingly, we found that both sterile and fertile males were more prone to predation than females, but we found no difference among males. The presence of sterile males significantly reduced Q-fly fertility, but the interaction of natural predators and sterile males did not significantly reduce the number of fertile eggs. Our findings highlight the important role of natural predators in controlling Q-flies together with SIT and provide a solid foundation for similar large-scale field trials using wild counterparts. © 2019 Society of Chemical Industry.

Isotopic Discrimination and Persistence of the 13C Marker in Adults of Anastrepha fraterculus (Diptera: Tephritidae) Brazilian-1 Morphotype

Stable carbon isotope ratios can be used to discriminate between wild and sterile insects that are caught in surveillance traps when 2 isotopically distinct dietary sources are available for the immature or adult stages. Artificial diets containing naturally 13C-labelled sugar can isotopically mark the adults of some tephritids, but when sexually mature flies are released in the field, their food source usually changes from a C4 to a C3 plant. Consequently, the isotopic composition of flies can change toward the isotopic signatures associated with the new diet. For isotope labelling to be more meaningful in a pest management program that integrates the sterile insect technique, it is important to know the persistence of the carbon isotope marker in field-release sterile adults. Therefore, this study was intended to assess the degree of isotopic differentiation between wild samples of Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) and flies reared on different artificial diets, and to estimate the turnover of carbon in flies after shifts to different adult diets. The whole bodies of flies reflected the overall isotopic composition of their larval diets immediately after emergence. When the adult diet was switched, the δ13C signatures of flies changed rapidly for 6 to 8 d, then reached an isotopic equilibrium with the final diet. Depletions up to -5.6 (parts per thousand) were observed in the signatures of flies switched from a C4 to a C3-based diet. However, appropriate feeding on diets with C4 sources ensured that the isotopic composition of larval diets was fixed in body structures of adult A. fraterculus, maintaining measurable 13C signals distinct from wild flies for 15 d after diet switching. No differences were found between males and females when they fed on different pre-release diets or after diet change. The 13C stable isotope proved to be a reliable marker for differentiating wild and laboratory-reared A. fraterculus flies.

Overexpression of an antioxidant enzyme improves male mating performance after stress in a lek-mating fruit fly

In many species, courtship displays are reliable signals of male quality, and current hypotheses suggest that these displays allow females to choose males with high cellular function. Environmental stressors generate excess reactive oxygen species (ROS) that impair cellular function, and thus antioxidant pathways that remove ROS are probably critical for preserving complex sexual behaviours. Here, we test the hypothesis that enhanced antioxidant activity in mitochondria preserves mating performance following oxidative stress. Using a transgenic approach, we directly manipulated mitochondrial antioxidant activity in the Caribbean fruit fly, Anastrepha suspensa, a lek-mating species with elaborate sexual displays and intense sexual selection that is also a model for sterile insect technique programmes. We generated seven transgenic lines that overexpress mitochondrial superoxide dismutase (MnSOD). Radiation is a severe oxidative stressor used to induce sterility for sterile insect programmes. After radiation treatment, two lines with intermediate MnSOD overexpression showed enhanced mating performance relative to wild-type males. These improvements in mating corresponded with reduced oxidative damage to lipids, demonstrating that MnSOD overexpression protects flies from oxidative stress at the cellular level. For lines with improved mating performance, overexpression also preserved locomotor activity, as indicated by a laboratory climbing assay. Our results show a clear link between oxidative stress, antioxidant capacity and male performance. Our work has implications for fundamentally understanding the role of antioxidants in sexual selection, and shows promise for using transgenic approaches to enhance the field performance of insects released for area-wide pest management strategies and improving performance of biological control agents in general.

RNAi-Mediated Knockdown of Tssk1 and Tektin1 Genes Impair Male Fertility in Bactrocera dorsalis.

The genetic-based sterile insect technique (SIT) is an effective and environmentally safe strategy to diminish populations of agricultural and horticultural insect pests. Functional characterization of genes related to male fertility can enhance the genetic-based SIT. Tssk1 has been involved to control male fertility in both mammals and insects. Moreover, Tektin1 has also been revealed to influence male fertility in both human and mammals. These findings suggested that Tssk1 and Tektin1 identified from Bactrocera dorsalis could be required for male fertility in B. dorsalis. In this study, expression profiles of these two genes were studied at different developmental stages and in various tissues of adult males. Remarkably, it was found that Tssk1 and Tektin1 were highly expressed in the testis of mature adult males of B. dorsalis. Furthermore, Tssk1 and Tektin1 genes were downregulated by using the RNA interference (RNAi) method. Fertility assays including egg laying, hatching, and spermatozoa count were also performed to investigate male fertility of B. dorsalis. Results showed that knockdown of Tssk1 and Tektin1 caused male sterility up to 58.99% and 64.49%, respectively. As expected, the total numbers of spermatozoa were also significantly reduced by 65.83% and 73.9%, respectively. These results suggested that male sterility was happened wing to the low number of spermatozoa. In conclusion, we demonstrate that Tssk1 and Tektin1 are the novel agents that could be used to enhance the genetic-based SIT, or their double-stranded RNA (dsRNA) can be used as biopesticides to control the population of B. dorsalis.

Implementation of control strategies for sterile insect techniques

In this paper, we propose a sex-structured entomological model that serves as a basis for design of control strategies relying on releases of sterile male mosquitoes (Aedes spp) and aiming at elimination of the wild vector population in some target locality. We consider different types of releases (constant and periodic impulsive), providing sufficient conditions to reach elimination. However, the main part of the paper is focused on the study of the periodic impulsive control in different situations. When the size of wild mosquito population cannot be assessed in real time, we propose the so-called open-loop control strategy that relies on periodic impulsive releases of sterile males with constant release size. Under this control mode, global convergence towards the mosquito-free equilibrium is proved on the grounds of sufficient condition that relates the size and frequency of releases. If periodic assessments (either synchronized with the releases or more sparse) of the wild population size are available in real time, we propose the so-called closed-loop control strategy, under which the release size is adjusted in accordance with the wild population size estimate. Finally, we propose a mixed control strategy that combines open-loop and closed-loop strategies. This control mode renders the best result, in terms of overall time needed to reach elimination and the number of releases to be effectively carried out during the whole release campaign, while requiring for a reasonable amount of released sterile insects.

Molecular characterisation of tomato leaf miner Tuta absoluta populations obtained from different geographical locations of India

The tomato leaf miner, Tuta absoluta (Meyrick) is one of the major invasive insect pests on solanaceous crops. T. absoluta distribution is observed in European, North African Mediterranean basin and Asian countries. The tomato leaf miner is spreading fast and affecting tomato production in both closed and open-field conditions. This insect pest has recently reported in various tomato growing regions of India and causing significant loss of production. In the present study, occurrence of a tomato leaf miner was studied by undertaking an extensive survey in tomato growing regions of India during September 2017 to May 2018. The infestation of T. absoluta was recorded in Maharashtra, Karnataka, Telangana, Tamil Nadu, Haryana and Himachal Pradesh. Severe incidence of T. absoluta infestation was recorded in Maharashtra (Nashik district) and Telangana (Mahabubnagar district) followed by Karnataka (Kalaburgi and Raichur districts). The moths collected during the survey were characterized using mitochondrial cytochrome c oxidase subunit I (COI) gene analysis. The T. absoluta samples showed maximum genetic similarity with KU565720 Kenya, KT452897 Oman, KY212128 South Africa, KY619687 India, KP814057 India and KJ657679 Florida. Nine T. absoluta populations were grouped under a single clade revealing no genetic variation within populations and showed high genetic homogeneity thereby the ideal candidate for sterile insect technique application. Further studies are required on population dynamics, host range, local and area-wide biological control management strategies for the effective management of T. absoluta .

Semi Field Trial Competitive Power Married Made Sterile Aedes Albopictus as Method of Vector Control: A Current Vector Controlling Method

Aedes albopictus is a plant that causes Dengue Hemorrhagic Fever is not as prevalent as Aedes Aegypti is not a disease given by Aedes albopictus mosquito is not much different from Aedes Aegypti mosquito. The Case Fatality Rate (CFR) of Dengue Fever is very high in Indonesia, at 41.4% at the beginning of dengue cases in Indonesia. Innovation continues to create for disease vector control to break the chain of disease. The use of sterile insect techniques is a useful thing in the things that need to be socialized in the community.

Biopesticides improve efficiency of the sterile insect technique for controlling mosquito-driven dengue epidemics

Various mosquito control methods use factory raised males to suppress vector densities. But the efficiency of these methods is currently insufficient to prevent epidemics of arbovirus diseases such as dengue, chikungunya or Zika. Suggestions that the sterile insect technique (SIT) could be “boosted” by applying biopesticides to sterile males remain unquantified. Here, we assess mathematically the gains to SIT for Aedes control of either: boosting with the pupicide pyriproxifen (BSIT); or, contaminating mosquitoes at auto-dissemination stations. Thresholds in sterile male release rate and competitiveness are identified, above which mosquitoes are eliminated asymptotically. Boosting reduces these thresholds and aids population destabilisation, even at sub-threshold release rates. No equivalent bifurcation exists in the auto-dissemination sub-model. Analysis suggests that BSIT can reduce by over 95% the total release required to circumvent dengue epidemics compared to SIT. We conclude, BSIT provides a powerful new tool for the integrated management of mosquito borne diseases.

Chilling, irradiation and transport of male Glossina palpalis gambiensis pupae: Effect on the emergence, flight ability and survival.

BackgroundThe sterile insect technique (SIT) requires mass-rearing of the target species, irradiation to induce sexual sterility and transportation from the mass-rearing facility to the target site. Those treatments require several steps that may affect the biological quality of sterile males. This study has been carried out to evaluate the relative impact of chilling, irradiation and transport on emergence rate, flight ability and survival of sterile male Glossina palpalis gambiensis.ResultsChilling, irradiation and transport all affected the quality control parameters studied. The emergence rate was significantly reduced by long chilling periods and transport, i.e. from 92% at the source insectary in Burkina Faso to 78% upon arrival in Senegal. Flight ability was affected by all three parameters with 31% operational flies lost between the production facility and the destination site. Only survival under stress was not affected by any of the treatments.ConclusionThe chilling period and transport were the main factors that impacted significantly the quality of sterile male pupae. Therefore, in the operational programme, the delivery of sterile male pupae was divided over two shipments per week to reduce the chilling time and improve the quality of the sterile males. Quality of the male pupae may further be improved by reducing the transport time and vibrations during transport.

Using machine learning to identify the geographical drivers of Ceratitis capitata trap catch in an agricultural landscape

The spatial distribution of Ceratitis capitata Wiedemann (Diptera: Tephritidae) trap catch was classified and related to a set of geographic variables to identify its main geographical drivers. Trap catch data were sourced from an area-wide integrated pest management (AW-IPM)1The integrated use of a combination of available management methods against a target pest including biological, chemical, and cultural management methods on an area-wide scale.1 programme and classified into statistically significant hot- and cold spots (HCSs)2Statistically significant spatial clusters of high values (hot spots) and low values (cold spots).2. Trap data of four consecutive fruiting seasons were combined to identify monthly and seasonal long-term HCSs. The main geographic drivers of the HCSs were identified using variable importance lists produced by the random forest (RF) machine learning (ML) algorithm. Long-term climate, topography, landscape and fruit fly management variables were used as predictor variables in RF to classify HCSs. The resulting RF models produced classification accuracies of up to 80%. In most cases, the most important variable was long-term rainfall, suggesting that this was the most prominent driver of C. capitata HCSs in our study region. The result of this study highlights the value of long-term pest monitoring data and long-term environmental data in understanding the spatial distribution of C. capitata trap catch in complex agricultural systems. This study sets out a framework to spatially quantify C. capitata trap catch into HCSs using monitoring data from AW-IPM programmes, enabling the investigation of complex ecological relationships through the use of ML algorithms. The results of these analyses could improve area-wide integrated fruit fly management programmes through more precise spatial planning of management actions, such as the sterile insect technique (SIT)3Biological environmentally-friendly insect pest control method.3, leading to better programme performance and reduced costs.