South American Fruit Fly Anastrepha Research Articles

Fine Scale Microevolutionary and Demographic Processes Shaping a Wild Metapopulation Dynamics of the South American Fruit Fly Anastrepha fraterculus.

Anastrepha fraterculus (Wiedmann)is an important American pest species. Knowledge of its population dynamics is of particular interest for ecology, evolutionary biology, and management programs. In the present study, phenotypic, genotypic, and spatial data were combined, within the frame of landscape genetics, to uncover the spatial population genetic structure (SGS) and demographic processes of an Argentinian local population from the Yungas ecoregion. Eight simple sequence repeats (SSR) loci and six morphometric traits were analysed considering the hierarchical levels: tree/fruit/individual. Genetic variability estimates were high (HE = 0.72, RA = 4.39). Multivariate analyses of phenotypic data showed that in average 52.81% of variance is explained by the tree level, followed by between individuals 28.37%. Spatial analysis of morphological traits revealed a negative autocorrelation in all cases. SGS analysis and isolation by distance based on SSR showed no significant autocorrelation for molecular coancestry. The comparison between phenotypic (PST) and molecular (FST) differentiation identified positive selection in different fruits for all traits. Bayesian analysis revealed a cryptic structure within the population, with three clusters spatially separated. The results of this study showed a metapopulation dynamics. The genetic background of the components of this metapopulation is expected to change through time due to seasonality, repopulation activities, and high gene flow, with an estimated dispersal ability of at least 10km. Effective population size (Ne) of the metapopulation was estimated in around 800 flies, and within subpopulations (clusters) Ne was associated with the levels of genetic drift experienced by the founding lineages.

Determining the Sterilization Doses under Hypoxia for the Novel Black Pupae Genetic Sexing Strain of Anastrepha fraterculus (Diptera, Tephritidae).

Simple SummaryThe sterile insect technique is an environmentally-friendly method that can be used to manage populations of the South American fruit fly Anastrepha fraterculus, but its sterilizing doses have been determined only under normoxia. To maintain sterile male fly quality without jeopardizing sterility, a strategy of applying the radiation dose under an oxygen-reduced atmosphere is commonly used. Therefore, this study tested a range of gamma radiation doses under hypoxia on pupae from a bisexual strain and a novel genetic sexing strain (GSS) of A. fraterculus. Four types of crosses between irradiated flies under hypoxia and nonirradiated flies of the bisexual strain were set to assess sterility for each strain and radiation dose. For males from both strains, the effect of radiation dose on the percentage of egg hatch, egg-to-pupa recovery, and recovery of adults were determined. A dose of 74 Gy reduced egg hatch by 99% regardless of the male strain and was considered the sterilizing dose. The fertility of irradiated females and development of their offspring were severely affected, even at low doses under hypoxia, and no eggs were laid with doses above 50 Gy.A common strategy used to maintain sterile fly quality without sacrificing sterility is to irradiate the insects under an oxygen-reduced atmosphere. So far, sterilizing doses for the South American fruit fly Anastrepha fraterculus have only been determined under normoxia. Our study reports for the first time the dose-sterility response under hypoxia for two different A. fraterculus strains. The pupae were derived from a bisexual strain (a Brazilian-1 population) and a recently developed genetic sexing strain (GSS-89). Two hours prior to irradiation, pupae were transferred to sealed glass bottles and irradiated when oxygen concentration was below 3%. Four types of crosses with nonirradiated flies of the bisexual strain were set to assess sterility for each radiation dose. For males from both strains, Weibull dose–response curves between radiation doses and the proportion of egg hatch, egg-to-pupa recovery, and recovery of adults were determined. The GSS males revealed high sterility/mortality levels compared to males from the bisexual strain at doses < 40 Gy, but a dose of 74 Gy reduced egg hatch by 99% regardless of the male strain and was considered the sterilizing dose. The fertility of irradiated females was severely affected even at low doses under hypoxia.

Identification and in situ hybridization to mitotic chromosomes of a molecular marker linked to maleness in Anastrepha fraterculus (Wied.)

The present report shows the molecular identification, isolation and citologically localization of a DNA-sequence from the South American fruit fly Anastrepha fraterculus (DIPTERA: Tephritidae) involved in sex- determination. It belongs to the Tephritidae family, the true fruit flies which are consider a pest of fruit crops. The sex determination system is of vital importance in the genetic control of the fruit fly pest: Sterile Insect Technique which unlike chemical control tactics, is environmentally friendly and does not pose any health concerns. We used in situ hybridization on mitotic chromosomes for localizing the primary sex determination factor in this fruit fly pest. Our results show that in Anastrepha fraterculus the Y chromosome is responsible for sex determination

Development and characterization of a pupal-colour based genetic sexing strain of Anastrepha fraterculus sp. 1 (Diptera: Tephritidae)

BackgroundArea-wide integrated pest management programs (AW-IPM) incorporating sterile insect technique (SIT) have been successful in suppressing populations of different fruit fly species during the last six decades. In addition, the development of genetic sexing strains (GSS) for different fruit fly species has allowed for sterile male-only releases and has significantly improved the efficacy and cost effectiveness of the SIT applications. The South American Fruit Fly Anastrepha fraterculus (Diptera: Tephritidae) is a major agricultural pest attacking several fruit commodities. This impedes international trade and has a significant negative impact on the local economies. Given the importance of sterile male-only releases, the development of a GSS for A. fraterculus would facilitate the implementation of an efficient and cost-effective SIT operational program against this insect pest species.ResultsFor potential use in a GSS, three new morphological markers (mutants) were isolated in a laboratory strain of A. fraterculus sp. 1, including the black pupae (bp) gene located on chromosome VI. The black pupa phenotype was used as a selectable marker to develop genetic sexing strains by linking the wild type allele (bp+) to the Y-chromosome -via irradiation to induce a reciprocal Y-autosome translocation. Four GSS were established and one of them, namely GSS-89, showed the best genetic stability and the highest fertility. This strain was selected for further characterization and cytogenetic analysis.ConclusionsWe herein report the development of the first genetic sexing strain of a major agricultural pest, A. fraterculus sp. 1, using as a selectable marker the black pupae genetic locus.

Larvicidal and Adulticidal Activities of Neem Oil against Anastrepha fraterculus (Wied.) (Tephritidae)

In the laboratory, a neem oil-based formulation was evaluated for its insecticidal potential against the South American fruit fly Anastrepha fraterculus (Wied.), as efficient alternative for growers harvest fruits more harmless for the human consumption. The commercial product was evaluated against eggs in vitro, guavas infested with eggs and young larvae, and adults. The application of 0.8% neem oil significantly reduced the larval hatching of A. fraterculus. Neem oil at 0.4, 0.6 and 0.8% significantly reduced the number of pupae and adults per fruit infested with eggs. Guava infested with A. fraterculus eggs and treated with neem oil at 0.8% exhibited a reduction of 90.0% and 92.6% of pupae and adults per fruit, respectively. The same dosage to guava infested by larvae achieved a 44.6 and 51.4% reduction of pupae and larvae, respectively. At 360 minutes after treatment, 0.8% of neem oil provided 67.9% of corrected adult mortality. This double insecticidal effect of neem oil and lack of phytotoxicity in ripe guavas at the tested concentrations demonstrate its potential in biorational management.

What Can Integrated Analysis of Morphological and Genetic Data Still Reveal about the Anastrepha fraterculus (Diptera: Tephritidae) Cryptic Species Complex?

The South American fruit fly Anastrepha fraterculus (Wiedemann) is a complex of cryptic species, the so-called “Anastrepha fraterculus complex”, for which eight morphotypes are currently recognized. A previous analysis of ITS1 in samples of the Anastrepha fraterculus complex, while revealing high distinctiveness among samples from different localities of South America, Central America, and Mexico, no direct association was made between sequence type and morphotype. In the present report, a correlated analysis of morphometry and ITS1 data involved individuals belonging to the same population samples. Although showing a low level of intra-populational nucleotide variability, the ITS1 analysis indicated numerous inter-population sequence type variants. Morphotypes identified by morphometric analysis based on female wing shape were highly concordant with ITS1 genetic data. The correlation of genetic divergence and morphological differences among the tested samples gives strong evidence of a robust dataset, thereby indicating the existence of various taxonomic species within the A. fraterculus complex. However, the data revealed genetic and morphological variations in some regions, suggesting that further analysis is still required for some geographic regions.

Spatial and temporal distribution of South American fruit fly in vineyards

ABSTRACT The South American fruit fly Anastrepha fraterculus (Wied., 1830) is one of the major insect pests of economic importance in vineyards of Southern Brazil. Understanding species behavior and knowing the moments when their population peaks occur can help producers and technicians to define management strategies. This work was carried out the spatial and temporal distribution of the A. fraterculus in two commercial vineyards of variety ‘Moscato Branco’ for two crop seasons. To evaluate the A. fraterculus distribution, we used the mass trapping system with handmade traps (transparent plastic bottles of polyethylene terephthalate - PET), baited with hydrolyzed protein CeraTrap™. The evaluations were performed every two weeks, counting the total number of adults found per trap in each vineyard. From the number of insects caught per trap, data analysis was performed using geostatistics, through semivariograms. The spatio-temporal fruit fly distribution was evaluated by thematic maps, using the inverse square distance interpolation. The semivariograms showed that most of the reviews were ‘pure nugget’ effect, indicating the absence of spatial data dependence. The spatio-temporal distribution maps allow us to assert that A. fraterculus shows invasive behavior in the vineyard, with its entry from the edges to the center, associated with the fruit ripening.

The South American Fruit Fly: An Important Pest Insect With RNAi-Sensitive Larval Stages.

RNA interference (RNAi) technology has been used in the development of approaches for pest control. The presence of some essential genes, the so-called “core genes,” in the RNAi machinery is crucial for its efficiency and robust response in gene silencing. Thus, our study was designed to examine whether the RNAi machinery is functional in the South American (SA) fruit fly Anastrepha fraterculus (Diptera: Tephritidae) and whether the sensitivity to the uptake of double-stranded RNA (dsRNA) could generate an RNAi response in this fruit fly species. To prepare a transcriptome database of the SA fruit fly, total RNA was extracted from all the life stages for later cDNA synthesis and Illumina sequencing. After the de novo transcriptome assembly and gene annotation, the transcriptome was screened for RNAi pathway genes, as well as the duplication or loss of genes and novel target genes to dsRNA delivery bioassays. The dsRNA delivery assay by soaking was performed in larvae to evaluate the gene-silencing of V-ATPase, and the upregulation of Dicer-2 and Argonaute-2 after dsRNA delivery was analyzed to verify the activation of siRNAi machinery. We tested the stability of dsRNA using dsGFP with an in vitro incubation of larvae body fluid (hemolymph). We identified 55 genes related to the RNAi machinery with duplication and loss for some genes and selected 143 different target genes related to biological processes involved in post-embryonic growth/development and reproduction of A. fraterculus. Larvae soaked in dsRNA (dsV-ATPase) solution showed a strong knockdown of V-ATPase after 48 h, and the expression of Dicer-2 and Argonaute-2 responded with an increase upon the exposure to dsRNA. Our data demonstrated the existence of a functional RNAi machinery in the SA fruit fly, and we present an easy and robust physiological bioassay with the larval stages that can further be used for screening of target genes at in vivo organisms’ level for RNAi-based control of fruit fly pests. This is the first study that provides evidence of a functional siRNA machinery in the SA fruit fly.

Development of Anastrepha fraterculus (Wiedemann, 1830) (Diptera: Tephritidae) in Different Host Fruits

The objective of this work was to determine the biological characteristics of South American fruit fly Anastrepha fraterculus (Wiedemann, 1830) (Diptera: Tephritidae) using three fruit hosts. Mature fruits of cherry (Eugenia involucrata DC. (Myrtaceae) (n = 200), guabiroba (Campomanesia xanthocarpa (Mart.) O. Berg. (Myrtaceae) (n=200) and apple Malus domestica Borkh. variety &amp;ldquo;Gala&amp;rdquo; (Rosaceae) (n = 100) were placed separately in plastic cages. These fruits were exposed to A. fraterculus for four hours for oviposition. On a daily basis, the resulting larvae and the pupa were separated. Studies on fertility and longevity used 25 pairs of adults that emerged from these fruits. A. fraterculus completed its biological cycle in all fruits tested. The period of development from egg to adult was shorter in fruits of C. xanthocarpa (25.9 days) and E. involucrata (28.6 days) than in those of M. domestica (34.7 days). The pre-oviposition period was shorter in adults, which emerged from fruits of C. xanthocarpa (9.9 days). The results show the importance of native host fruits for population growth of A. fraterculus, and probably, for host availability of larvae of A. fraterculus for natural and applied biological control in the Southern Cone of South America region.

Cryptic genetic structure in an Argentinian population of Anastrepha fraterculus (Diptera: Tephritidae) evidenced by SSR markers and quantitative traits

In some regions of Argentina and Brazil, the South American fruit fly Anastrepha fraterculus (Wied.) (Diptera: Tephritidae) causes significant damage to crops. An efficient integrated management program requires knowledge of pest population dynamics, dispersion patterns, sexual and oviposition behaviour, and adaptive landscape. The present study combined simple sequence repeat (SSR) molecular markers and morphometric datasets in order to analyse the population structure and infer the oviposition resource use strategy of the females. Infested guava fruits were collected from nine wild trees in Tucuman, Argentina, and a total of 140 adult A. fraterculus were recovered. These were then measured for six morphometric traits and 89 of them were genotyped for eight SSR loci. Genetic variability estimates were high (expected heterozygosity = 0.71, allelic richness = 12.5), with 8 to 20 alleles per locus. According to Wright's F-statistics estimates, the highest proportion (83%) of genetic variation occurred within individuals while variance between and within fruits were similar (≈ 8.5%). Analysis of the cryptic genetic structure based on SSR using different approaches, namely discriminant analysis of principal components (DAPC) and sparse non-negative matrix factorization (SNMF), yielded results consistent with the occurrence of two clusters with virtually no admixture. Average kinship between individuals which had emerged from the same fruit (0.07) was lower than that expected for full-sib families. Univariate and multivariate analyses of phenotypic data showed 54-66% of variance among individuals within fruits and 34-46% among fruits. The comparison between phenotypic (PST) and molecular (FST) differentiation identified wing width and length as possible target of positive selection. The average kinship and high genetic variation within fruits, together with the highly significant genetic differentiation among fruits, supports the hypothesis that each fruit was colonised by about three ovipositing females. The results also indicate that females were able to disperse widely from the emergence site before mating and starting oviposition activity.

Toxicity and residual effects of toxic baits with spinosyns on the South American fruit fly

Abstract: The objective of this work was to assess the lethal concentration and lethal time (LC and LT) of spinosad and spinetoram, combined with different food lures, and their residual effects on South American fruit fly (Anastrepha fraterculus). The toxic baits were offered in eight concentrations (2, 6, 14, 35, 84, 204, 495, and 1,200 mg L-1), combined with the following food lures: 7% sugarcane molasses, 3% Biofruit, 1.5% CeraTrap, 1.25% Flyral, 3% Samaritá Bait, and 3% Samaritá Tradicional; diluted food lures in water were used as controls. The residual effect of the formulations at 96 mg L-1 concentration were evaluated for 21 days and were compared with that of the commercial bait Success 0.02 CB. Both insecticides were toxic to adults of A. fraterculus, and mortality varied with the food lure used. The LC50and LT50ranged from 15.19 to 318.86 mg L-1and from 11.43 to 85.93 hours, respectively. Spinosad was 2 to 36 times as toxic as spinetoram when combined with different hydrolyzed proteins. Toxic baits formulated with spinosad and spinetoram (96 mg L-1) caused mortality equivalent to the one by Success 0.02 CB (90.2%), when assessed on the day of application. Toxic baits formulated with 3% Biofruit + spinosad and 3% Samaritá Bait + spinetoram are effective for managingA. fraterculusand provide up to seven days of residual effect in the absence of rain; however, only Success 0.02 CB caused more than 80% mortality for up to 21 days.

Sequential mate choice in the South American fruit fly: the role of male nutrition, female size and host availability on female remating behaviour

After mating, female sexual receptivity usually decreases and returns, depending on various factors, one of which can be the quality of the first or second male. Here, we tested in the South American fruit fly Anastrepha fraterculus if female remating is conditioned by the quality of the second male, when females encounter sequential mates (under no-choice conditions) and when females have the opportunity to choose between well-nourished and malnourished males, both for mating and for remating. Additionally, we tested if other factors such as female size and the opportunity to oviposit influenced females’ remating propensity. We found that females remate more often when they encounter a male of good nutritional condition, under both choice and no-choice conditions, and when females had access to a host to oviposit. Other traits of the sequential mate, such as male mating status (virgin or mated), male density (one or three males) and female size, had no effect on female remating behaviour. Plasticity in female post-copulatory mating under both choice and no-choice conditions indicates that A. fraterculus females are able to discriminate between males with different nutritional qualities without needing to compare them directly. Females were more choosy when remating, probably as a result of previous sexual experience, yet it remains to be seen which cues females use to distinguish between males. We discuss our results in the context of female pre- and post-copulatory mating decisions.

Evolutionary coincidence of adaptive changes in exuperantia and the emergence of bicoid in Cyclorrhapha (Diptera)

The great radiation in the infraorder Cyclorrhapha involved several morphological and molecular changes, including important changes in anterior egg development. During Drosophila oogenesis, exuperantia (exu) is critical for localizing bicoid (bcd) messenger RNA (mRNA) to the anterior region of the oocyte. Because it is phylogenetically older than bcd, which is exclusive to Cyclorrhapha, we hypothesize that exu has undergone adaptive changes to enable this new function. Although exu has been well studied in Drosophila, there is no functional or transcriptional information about it in any other Diptera. Here, we investigate exu in the South American fruit fly Anastrepha fraterculus, a Cyclorrhapha of great agricultural importance that have lost bcd, aiming to understand the evolution of exu in this infraorder. We assessed its pattern of gene expression in A. fraterculus by analyzing transcriptomes from cephalic and reproductive tissues. A combination of next-generation data with classical sequencing procedures enabled identification of the structure of exu and its alternative transcripts in this species. In addition to the sex-specific isoforms described for Drosophila, we found that not only exu is expressed in heads, but this is mediated by two transcripts with a specific 5′UTR exon—likely a result from usage of a third promoter. Furthermore, we tested the hypothesis that exu is evolving under positive selection in Cyclorrhapha after divergence from lower Diptera. We found evidence of positive selection at two important exu domains, EXO-like and SAM-like, both involved with mRNA binding during bcd mRNA localization in Drosophila, which could reflect its cooptation for the new function of bcd mRNA localization in Cyclorrhapha.

Male sexual enhancement after methoprene treatment in Anastrepha fraterculus (Diptera: Tephritidae): A sustained response that does not fade away after sexual maturation

The juvenile hormone (JH) of insects triggers physiological changes related to reproduction in adults of both sexes. Methoprene is a sesquiterpene with some effects that are analogous to those of JH. Treatments with methoprene accelerate sexual maturation in males of the South American fruit fly Anastrepha fraterculus, giving young males a mating advantage over non-treated males of the same age. Here, we evaluated the effects of methoprene treatment on A. fraterculus males after the sexual maturation phase and tested whether this compound provides a long-term mating advantage. Moreover, we took the first step to unravel the mechanisms that underlie male sexual enhancement. We treated males 1day or 8days after adult emergence and compared mate choice between recently matured (young) females and females that had been mature for ca. 10days (aged females). We also addressed methoprene treatment effects on male sexual signalling. We found that methoprene treatment enhanced male sexual competitiveness even after the sexual maturation phase, and the effect did not decrease until males were older than 20days. However, when methoprene treatment was carried out close to sexual maturity, the mating enhancement was no longer observed, suggesting a non-immediate effect and excluding the possibility that methoprene acts as a pheromonal compound. Young and aged females tended to mate more frequently with treated-males. This might indicate that in a context of sexual selection, the potential benefits associated with reproductive success would be similar for females of both ages. Treated males released larger amounts of pheromonal compounds than non-treated males, but their courtship behaviour was not altered to the same extent, suggesting that methoprene treatment may accelerate differently the components of male courtship. We discuss potential benefits of using methoprene to increase the efficiency of the sterile insect technique, which is an environmentally safe method to control this important South American fruit pest.

The male ejaculate as inhibitor of female remating in two tephritid flies

The inhibition of female receptivity after copulation is usually related to the quality of the first mating. Males are able to modulate female receptivity through various mechanisms. Among these is the transfer of the ejaculate composed mainly by sperm and accessory gland proteins (AGPs). Here we used the South American fruit fly Anastrepha fraterculus (where AGP injections inhibit female receptivity) and the Mexican fruit fly Anastrepha ludens (where injection of AGPs failed to inhibit receptivity) as study organisms to test which mechanisms are used by males to prevent remating. In both species, neither the act of copulation without ejaculate transfer nor sperm stored inhibited female receptivity. Moreover, using multiply mated sterile and wild males in Mex flies we showed that the number of sperm stored by females varied according to male fertility status and number of previous matings, while female remating did not. We suggest female receptivity in both flies is inhibited by the mechanical and/or physiological effect of the full ejaculate. This finding brings us closer to understanding the mechanisms through which female receptivity can be modulated.

Efeito de Iscas Tóxicas sobre Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae)

Uma alternativa para a supressão populacional de Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) é o emprego de iscas tóxicas. Nesse estudo, foi avaliado em laboratório o efeito de ingestão de formulações de iscas tóxicas sobre adultos de A. fraterculus bem como o efeito da precipitação pluvial sobre a eficiência das iscas. As formulações avaliadas foram: a) ANAMED® (SPLAT® 40,00% + atrativo 24,20% + espinosade 0,10%); b) Success* 0,02 CB® – (atrativos + espinosade 0,02%); c) proteína hidrolisada (Biofruit® 3%) + Malathion 1000 CE (0,15%) e d) Testemunha – água destilada. A mortalidade proporcionada pelas formulações contendo espinosade (ANAMED® e Success* 0,02 CB®) foi equivalente à formulação Biofruit® + Malathion 16 horas após a aplicação dos tratamentos (HAT). Na ausência de chuva, as três formulações foram eficazes (mortalidade superior a 90%) até 21 dias após a aplicação dos tratamentos (DAT). As formulações ANAMED® + espinosade e Success* 0,02 CB® promoveram elevada mortalidade (60,0 e 64,0%, respectivamente) até 28 DAT. Com chuva simulada de 20 e 50 mm, a mortalidade promovida pela formulação ANAMED® foi de 69,2 e 41,0%, respectivente, diferindo das demais formulações. A isca tóxica Biofruit® + Malathion apresentou o menor TL (tempo letal) 50 com 8,71 horas, seguida de ANAMED® e Success* 0,02 CB® com 11,78 e 12,61 horas, respectivamente. As formulações Success* 0,02 CB® e ANAMED® + espinosade apresentaram alta eficiência no controle de adultos de A. fraterculus na ausência de chuva. Sob lâminas de 20 e 50 mm de chuva simulada., ANAMED® apresenta maior eficiência no controle de adultos de A. fraterculus que as formulações Success* 0,02 CB® e Biofruit® + Malathion.

Current Sperm Competition Determines Sperm Allocation in a Tephritid Fruit Fly

Sperm competition (SC) occurs when the sperm of two or more males compete for the same set of ova. Theoretical models and experimental observations indicate that the presence of rival males causes focal males to adjust sperm allocation in a given copulation. Males allocate more sperm when they perceive the presence of one rival male (SC risk), either before or during mating, or when they perceive the presence of multiple rival males before mating (previous SC intensity). Conversely, males are expected to allocate fewer sperm when they perceive the presence of rival males during mating (current SC intensity). Here, we varied male perception of SC by manipulating the number of rival males, both before mating (from emergence to mating) and during mating (at the time of mating) to examine their effects on mating latency, copulation duration, and sperm allocation in the South American fruit fly Anastrepha fraterculus. We showed that exposure to rival males at the time of mating decreased mating latency. However, in contrast to the theory, exposure to multiple rivals at the time of mating increased sperm allocation. Female and male size were significant predictors of mating latency, copulation duration, and sperm allocation. Our results showed that there is a plastic response of males to the level of perceived SC through the number of rival males. Current levels of SC intensity are important in shaping male responses to SC, although the patterns in this species are opposite to predictions from the existing theory. We propose that female preference for males forming leks could explain lower sperm counts when encountering only one or two males.

Genetics and biology of Anastrepha fraterculus: research supporting the use of the sterile insect technique (SIT) to control this pest in Argentina.

Two species of true fruit flies (taxonomic family Tephritidae) are considered pests of fruit and vegetable production in Argentina: the cosmopolitan Mediterranean fruit fly (Ceratitis capitata Wiedemann) and the new world South American fruit fly (Anastrepha fraterculus Wiedemann). The distribution of these two species in Argentina overlaps north of the capital, Buenos Aires. Regarding the control of these two pests, the varied geographical fruit producing regions in Argentina are in different fly control situations. One part is under a programme using the sterile insect technique (SIT) for the eradication of C. capitata, because A. fraterculus is not present in this area. The application of the SIT to control C. capitata north of the present line with the possibility of A. fraterculus occupying the niche left vacant by C. capitata becomes a cause of much concern. Only initial steps have been taken to investigate the genetics and biology of A. fraterculus. Consequently, only fragmentary information has been recorded in the literature regarding the use of SIT to control this species. For these reasons, the research to develop a SIT protocol to control A. fraterculus is greatly needed. In recent years, research groups have been building a network in Argentina in order to address particular aspects of the development of the SIT for Anastrepha fraterculus. The problems being addressed by these groups include improvement of artificial diets, facilitation of insect mass rearing, radiation doses and conditions for insect sterilisation, basic knowledge supporting the development of males-only strains, reduction of male maturation time to facilitate releases, identification and isolation of chemical communication signals, and a good deal of population genetic studies. This paper is the product of a concerted effort to gather all this knowledge scattered in numerous and often hard-to-access reports and papers and summarize their basic conclusions in a single publication.

Morphometric trait differentiation between a wild and a mass-reared population of Anastrepha fraterculus (Diptera: Tephritidae)

The South American fruit fly Anastrepha fraterculus (Wiedemann) is an important pest in many countries. The sterile insect technique is an effective method of controlling Ceratitis capitata (Wiedemann) in Argentina and has been proposed for use against A. fraterculus. Because this technique relies on sterile mass-reared males mating with wild females, it is essential to verify that artificial rearing does not reduce male mating competitiveness. Several morphometric characters were evaluated to detect differences between a wild population and a laboratory strain that was derived from it and reared artificially since 1997. Eight morphometric traits were analysed as indicators of body size, head shape and potential mobility: Thorax Length, Head Width, Face Width, Eye Length, Wing Length, Wing Width, Third Tibia Length and Femur Length. The results were analysed using multivariate analysis of variance, linear multiple regression and logistic multiple regression. In general, laboratory flies were larger than wild ones (possibly because the larval diet was supplied ad libitum). Laboratory males had significantly larger Head Width and Eye Length and a smaller Wing Width than wild males. Laboratory females differed from wild ones only by having narrower wings. These results could be due to environmental and genetic factors, or as a consequence of genetic drift (for the latter) during colony establishment plus gradual adaptation to laboratory conditions, where flight ability is most likely less important (resources are found easily at close distances). Also, short-distance interactions among individuals are more frequent in a colony, possibly favouring increased facial trait sizes by sexual selection. Because long-term morphological changes could represent the beginning of intraspecific differentiation, they should probably be worthy of some consideration if a large mass-rearing colony is established.

Developing a mass-rearing system for Anastrepha fraterculus (Diptera: Tephritidae) in north-eastern Brazil

Fruit fly pests in north-eastern Brazil include several species of the genus Anastrepha and the Mediterranean fruit fly Ceratitis capitata (Wiedemann). The most common species are Anastrepha zenildae Zucchi, the South American fruit fly Anastrepha fraterculus (Wiedemann), the West Indian fruit fly Anastrepha obliqua (Macquart) and Anastrepha sororcula Zucchi. In this study, attempts were made to mass-rear A. zenildae and A. fraterculus. The objective was to adapt local populations to laboratory conditions and develop mass-rearing systems for further utilization in integrated area-wide control programmes. Small colonies initially fed on guava fruits were developed in the laboratory. Adults were fed a diet made of brown sugar (60%), hydrolysed corn protein (26%), brewer’s yeast (5%) and honey (9%). Adult diets with other combinations of ingredients were also tested. The colonies of A. zenildae and A. fraterculus achieved mating and egg hatch rates of 32 and 39%, respectively. The best diets for adults, resulting in good egg hatch, were as follows: diet B — brown sugar (60%), hydrolysed corn protein (26%), brewer’s yeast (5%) and honey (5%); diet C — hydrolysed corn protein and white sugar (1:3); and diet D — soybean protein and white sugar (1:3). The best larval diet was based on 18% sugarcane bagasse and 9% protein. Adult mortality during the first 15 days was still high, over 50%. Adult recovery from pupae was over 70%. The best oviposition substrate was an agar-coated glass bottle. Mating compatibility was highest for A. fraterculus from the state of Sao Paulo. Mating between A. fraterculus and A. zenildae yielded no viable eggs.