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Studies investigating oviposition preference of Ceratitis capitata (Wiedemann, 1824) in table grapes (Vitis vinifera L.) cultivated in the São Francisco River Valley can provide important information to guide control measures, therefore minimizing damage caused by this species in the region. The aim of this study was to evaluate the oviposition preference of C. capitata females for berries cv. ?Italia? collected at five different times (60, 70, 80, 90, and 100 d after production pruning [DAPP]), representing five grapevine growth stages. We also assessed the performance of immature stages of C. capitata regarding the physiological development of the berry. The total soluble solid content was significantly higher in berries at more advanced physiological developmental stages (90 and 100 DAPP). Conversely, these berries showed the lowest values of firmness and titratable acidity. With the onset of physiological development, the average number of punctures per berry increased and reached 5.2 per berry in 100 DAPP berries. The infestation level and pupal weight showed a positive correlation with the growth stage. The highest recovery of pupae was observed in 100 DAPP berries (1.54). Pupal viability values ranged from 50.9 to 64.7% independent of berry maturity stage. The physiological developmental stage of the berry did not affect offspring sex ratio. Results obtained suggest that regardless of the female preference for laying eggs on berries in a more advanced physiological developmental stage, females can initiate the attack to bunches of this cultivar at 60 DAPP, even if the berries have unfavorable physicochemical parameters for oviposition and development of larvae. Made available in DSpace on 2019-04-17T01:11:32Z (GMT). No. of bitstreams: 1 Dora2019.pdf: 260987 bytes, checksum: 0af251dd906340390ebad03c3f4e7555 (MD5) Previous issue date: 2019

The success of the sterile insect technique (SIT) depends on the ability of sterile males to compete effectively with wild males to mate with wild females. This study compared the sexual competitiveness and other behavioral parameters of males of two strains of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), tsl Vienna 8 (tsl V-8) and the transgenic line OX3864A, in competition with wild males from the Sao Francisco Valley region in Bahia, Brazil. Mating events were observed in field cages containing virgin, sexually mature insects as follows: 50 wild females (10–12 days old), 50 wild males (8–10 days old), and either 50 tsl V-8 sterile males (5 days old) or 50 transgenic males (3–4 days old). In addition to scoring male type for each mating event, we also monitored the location of mating events within the tree canopy, mating duration, and mating latency. The proportion of females that mated did not differ between the two competition scenarios tested (tsl V-8 vs. wild males: 0.65 ± 0.04; transgenic vs. wild males: 0.64 ± 0.03). Relative sterility index did not differ between sterile (0.34 ± 0.04) and transgenic males (0.31 ± 0.03). The latency period was significantly longer for transgenic males (84.90 ± 4.87 min) than for sterile (65.24 ± 4.65 min) and wild males (66.61 ± 2.66 min). Mating events involving the three strains occurred in the same area of the tree, i.e., mid-height, in the central sector and on leaf undersurfaces. The mean duration of mating events involving sterile (94.1 ± 3.59 min) and transgenic males (81.1 ± 3.54 min) were both significantly shorter than for wild males (123.3 ± 1.93 min). Further investigation is suggested to assess other behavioral parameters, such as the amount of sperm transferred by transgenic males, their ability to disperse and survive in the field conditions, and their capacity to prevent females remating with wild males, in order to determine the potential of this transgenic strain for inclusion in the Brazilian SIT programs.

In an attempt to control the mosquito-borne diseases yellow fever, dengue, chikungunya, and Zika fevers, a strain of transgenically modified Aedes aegypti mosquitoes containing a dominant lethal gene has been developed by a commercial company, Oxitec Ltd. If lethality is complete, releasing this strain should only reduce population size and not affect the genetics of the target populations. Approximately 450 thousand males of this strain were released each week for 27 months in Jacobina, Bahia, Brazil. We genotyped the release strain and the target Jacobina population before releases began for21,000 single nucleotide polymorphisms (SNPs). Genetic sampling from the target population six, 12, and 27-30 months after releases commenced provides clear evidence that portions of the transgenic strain genome have been incorporated into the target population. Evidently, rare viable hybrid offspring between the release strain and the Jacobina population are sufficiently robust to be able to reproduce in nature. The release strain was developed using a strain originally from Cuba, then outcrossed to a Mexican population. Thus, Jacobina Ae. aegypti are now a mix of three populations. It is unclear how this may affect disease transmission or affect other efforts to control these dangerous vectors. These results highlight the importance of having in place a genetic monitoring program during such releases to detect un-anticipated outcomes.

International audience; Major efforts are currently underway to develop novel, complementary methods to combat mosquito-borne diseases. Mosquito genetic control strategies (GCSs) have become an increasingly important area of research on account of their species-specificity, track record in targeting agricultural insect pests, and their environmentally non-polluting nature. A number of programs targeting Aedes and Anopheles mosquitoes, vectors of human arboviruses and malaria respectively, are currently being developed or deployed in many parts of the world. Operationally implementing these technologies on a large scale however, beyond proof-of-concept pilot programs, is hampered by the absence of adequate sex separation methods. Sex separation eliminates females in the laboratory from male mosquitoes prior to release. Despite the need for sex separation for the control of mosquitoes, there have been limited efforts in recent years in developing systems that are fit-for-purpose. In this special issue of Parasites and Vectors we report on the progress of the global Coordinated Research Program on Exploring genetic, molecular, mechanical and behavioural methods for sex separation in mosquitoes that is led by the Insect Pest Control Subprogramme of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture with the specific aim of building efficient sex separation systems for mosquito species. In an effort to overcome current barriers we briefly highlight what we believe are the three main reasons why progress has been so slow in developing appropriate sex separation systems: the availability of methods that are not scalable, the difficulty of building the ideal genetic systems and, finally, the lack of research efforts in this area.

The number of mosquito populations resistant to insecticides is increasing along with the reemerging of vector-borne diseases. New technologies are under evaluation to complement the strategies used against these mosquitoes. Transgenic mosquitoes are one approach that some countries are considering and they are being evaluated to control the wild population. Although they have achieved success in population suppression of Aedes aegypti (L.) (Diptera: Culicidae), these studies have not demonstrated what the outcomes are when releases are interrupted (ceased). In this study, after demonstrating suppression of Ae. aegypti using transgenic technology, changes in the spatial distribution of the infestation and the abundance of the vector Ae. aegypti were assessed in the post-release period, along with fluctuation of transgenic mosquitoes in two areas of Brazil. In both pilot trials, there was an average suppression of ca. 70% of the wild population due to the release of transgenic males compared to the pre-release period. In Juazeiro (Mandacaru), in the post-release phase, the number of eggs per trap ranged between 0.06 and 14.41 (mean ± SE = 4.44 ± 0.44), and the ovitrap index (OI = number of ovitraps with eggs/total number of ovitraps recovered) ranged from 0.01 to 0.43 (0.13 ± 0.01). In Jacobina (Pedra Branca), during the post-release phase, the number of eggs per trap ranged between 1 and 7.2 (1.72 ± 0.72), and the OI ranged from 1 to 0.83 (0.095 ± 0.032). The mosquito population in Juazeiro (Mandacaru) remained suppressed for 17 weeks after the release interruption, whereas in Jacobina (Pedra Branca) suppression lasted 32 weeks. In Juazeiro, transgenic larvae were detected up to 5 months after the interruption of the over-flooding releases of transgenic males. In Jacobina, they were found up to 2 months after the release interruption. The number of eggs collected increased 4–5 months after the release interruption, which indicated that the Ae. aegypti population had been re-established after the interruption of releases. The results demonstrate that the technique requires a continuous release in the treated areas, and after suppression, the release rate can be decreased and used as a barrier against external migration.

Ceratitis capitata is one of the most important pests of fruits for exportation, and Sterile Insect Technique (SIT) has been the most efficient and environmental friendly technique used to control fruit fly populations around the world. A key goal in achieving a successful SIT program is a mass rearing system producing high quality insects at low cost. Providing adults with an artificial diet containing hydrolysed protein has been the major obstacle for bio-production facilities in Brazil, because it is expensive and has to be imported. Two other commercial products, autolysed yeast (AY) and yeast extract (YE), of domestic origin and low cost, were tested as substitutes of the imported hydrolyzed protein. To compare their efficiency we observed the female fecundity, adult survival and egg viability of flies raised on diets containing one of each of the different protein products. Flies reared on the domestic yeast products had equivalent or superior performance to the flies reared on imported protein. Both AY and YE can be a possible substitute for imported hydrolyzed protein for C. capitata mass-rearing, as they are cheaper and are readily available in the national market.

New techniques and methods are being sought to try to win the battle against mosquitoes. Recent advances in molecular techniques have led to the development of new and innovative methods of mosquito control based around the Sterile Insect Technique (SIT)(1-3). A control method known as RIDL (Release of Insects carrying a Dominant Lethal)(4), is based around SIT, but uses genetic methods to remove the need for radiation-sterilization(5-8). A RIDL strain of Ae. aegypti was successfully tested in the field in Grand Cayman(9,10); further field use is planned or in progress in other countries around the world. Mass rearing of insects has been established in several insect species and to levels of billions a week. However, in mosquitoes, rearing has generally been performed on a much smaller scale, with most large scale rearing being performed in the 1970s and 80s. For a RIDL program it is desirable to release as few females as possible as they bite and transmit disease. In a mass rearing program there are several stages to produce the males to be released: egg production, rearing eggs until pupation, and then sorting males from females before release. These males are then used for a RIDL control program, released as either pupae or adults(11,12). To suppress a mosquito population using RIDL a large number of high quality male adults need to be reared(13,14). The following describes the methods for the mass rearing of OX513A, a RIDL strain of Ae. aegypti (8), for release and covers the techniques required for the production of eggs and mass rearing RIDL males for a control program.

New techniques and methods are being sought to try to win the battle against mosquitoes. Recent advances in molecular techniques have led to the development of new and innovative methods of mosquito control based around the Sterile Insect Technique (SIT)(1-3). A control method known as RIDL (Release of Insects carrying a Dominant Lethal)(4), is based around SIT, but uses genetic methods to remove the need for radiation-sterilization(5-8). A RIDL strain of Ae. aegypti was successfully tested in the field in Grand Cayman(9,10); further field use is planned or in progress in other countries around the world. Mass rearing of insects has been established in several insect species and to levels of billions a week. However, in mosquitoes, rearing has generally been performed on a much smaller scale, with most large scale rearing being performed in the 1970s and 80s. For a RIDL program it is desirable to release as few females as possible as they bite and transmit disease. In a mass rearing program there are several stages to produce the males to be released: egg production, rearing eggs until pupation, and then sorting males from females before release. These males are then used for a RIDL control program, released as either pupae or adults(11,12). To suppress a mosquito population using RIDL a large number of high quality male adults need to be reared(13,14). The following describes the methods for the mass rearing of OX513A, a RIDL strain of Ae. aegypti (8), for release and covers the techniques required for the production of eggs and mass rearing RIDL males for a control program.

Genetic control methods of mosquito vectors of malaria, dengue, yellow fever, and Zika are becoming increasingly popular due to the limitations of other techniques such as the use of insecticides. The sterile insect technique is an effective genetic control method to manage insect populations. However, it is crucial to release sterile mosquitoes by air to ensure homogeneous coverage, especially in large areas. Here, we report a fully automated adult mosquito release system operated from an uncrewed aerial vehicle or drone. Our system, developed and tested in Brazil, enabled a homogeneous dispersal of sterile male Aedes aegypti while maintaining their quality, leading to a homogeneous sterile-to-wild male ratio due to their aggregation in the same sites. Our results indicate that the released sterile males were able to compete with the wild males in mating with the wild females; thus, the sterile males were able to induce sterility in the native female population. The use of drones to implement the sterile insect technique will lead to improvements in areal coverage and savings in operational costs due to the requirement of fewer release sites and field staff.; Genetic control methods of mosquito vectors of malaria, dengue, yellow fever, and Zika are becoming increasingly popular due to the limitations of other techniques such as the use of insecticides. The sterile insect technique is an effective genetic control method to manage insect populations. However, it is crucial to release sterile mosquitoes by air to ensure homogeneous coverage, especially in large areas. Here, we report a fully automated adult mosquito release system operated from an uncrewed aerial vehicle or drone. Our system, developed and tested in Brazil, enabled a homogeneous dispersal of sterile male Aedes aegypti while maintaining their quality, leading to a homogeneous sterile-to-wild male ratio due to their aggregation in the same sites. Our results indicate that the released sterile males were able to compete with the wild males in mating with the wild females; thus, the sterile males were able to induce sterility in the native female population. The use of drones to implement the sterile insect technique will lead to improvements in areal coverage and savings in operational costs due to the requirement of fewer release sites and field staff.