On the impact of re-mating and residual fertility on the Sterile Insect Technique efficacy: Case study with the medfly, Ceratitis capitata

The sterile insect technique (SIT) can be an efficient solution for reducing or eliminating certain insect pest populations. It is widely used in agriculture against fruit flies, including the Mediterranean fruit fly (medfly), Ceratitis capitata. The re-mating tendency of medfly females and the fact that the released sterile males may have some residual fertility could be a challenge for the successful implementation of the SIT. Obtaining the right balance between sterility level and sterile male quality (competitiveness, longevity, etc) is the key to a cost-efficient program. Since field experimental approaches can be impacted by many environmental variables, it is difficult to get a clear understanding on how specific parameters, alone or in combination, may affect the SIT efficiency. The use of models not only helps to gather knowledge, but it allows the simulation of a wide range of scenarios and can be easily adapted to local populations and sterile male production. In this study, we consider single- and double-mated females. We first show that SIT can be successful only if the residual fertility is less than a threshold value that depends on the basic offspring number of the targeted pest population, the re-mating rates, and the parameters of double-mated females. Then, we show how the sterile male release rate is affected by the parameters of double-mated females and the male residual fertility. Different scenarios are explored with continuous and periodic sterile male releases, with and without ginger aromatherapy, which is known to enhance sterile male competitiveness, and also taking into account some biological parameters related to females that have been mated twice, either first by a wild (sterile) male and then a sterile (wild) male, or by two wild males only. Parameter values were chosen for peach as host fruit to reflect what could be expected in the Corsican context, where SIT against the medfly is under consideration. Our results suggest that ginger aromatherapy can be a decisive factor determining the success of SIT against medfly. We also emphasize the importance of estimating the duration of the refractory period between matings depending on whether a wild female has mated with a wild or sterile male. Further, we show the importance of parameters, like the (hatched) eggs deposit rate and the death-rate related to all fertile double-mated females. In general, re-mating is considered to be detrimental to SIT programs. However, our results show that, depending on the parameter values of double-mated females, re-mating may also be beneficial for SIT. Our model can be easily adapted to different contexts and species, for a broader understanding of release strategies and management options.

Evidence that recent climatic changes have expanded the potential geographical range of the Mediterranean fruit fly

The species distributions migration poleward and into higher altitudes in a warming climate is especially concerning for economically important insect pest species, as their introduction can potentially occur in places previously considered unsuitable for year-round survival. We explore the expansion of the climatically suitable areas for a horticultural pest, the Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera, Tephritidae), with an emphasis on Europe and California. We reviewed and refined a published CLIMEX model for C. capitata, taking into consideration new records in marginal locations, with a particular focus on Europe. To assess the model fit and to aid in interpreting the meaning of the new European distribution records, we used a time series climate dataset to explore the temporal patterns of climate suitability for C. capitata from 1970 to 2019. At selected bellwether sites in Europe, we found statistically significant trends in increasing climate suitability, as well as a substantial northward expansion in the modelled potential range. In California, we also found a significant trend of northward and altitudinal expansion of areas suitable for C. capitata establishment. These results provide further evidence of climate change impacts on species distributions and the need for innovative responses to increased invasion threats.

Probiotic consortium modulating the gut microbiota composition and function of sterile Mediterranean fruit flies

The sterile insect technique (SIT) remains a successful approach in managing pest insects. However, the long-term mass rearing and sterilizing radiation associated with SIT have been observed to induce physiological and ecological fitness decline in target insects. This decline may be attributed to various factors, including commensal microbiota dysbiosis, selection procedures, loss of heterozygosity, and other complex interactions.. There is evidence that the bacterial symbiont of insects may play critical roles in digestion, development, reproduction, and behavior. Probiotics are an increasingly common approach for restoring the intestinal microbiota structure and fitness parameters of sterile insects, particularly in the Vienna 8 genetic sexing strain (V8-GSS) of the Mediterranean fruit fly (medfly), Ceratitis capitata. Here, we explore the influence of the previously isolated bacterial strain, Lactococcus lactis, Enterobacter sp., and Klebsiella oxytoca, administration as probiotic consortia (LEK-PC) to the larvae and/or adult diet over the course of 20 rearing generations on fitness parameters. The experiment was carried out in four colonies: a control colony (C), one to which probiotics were not added, one to which probiotics were added to the larval medium (L+), one to which probiotics were added to the adult medium (A+), and one to which probiotics were added to both the larval and adult mediums (AL+). Emergence, flight ability, survival under stress conditions, and mating competitiveness, were all significantly improved by the LEK-PC treatment independently of the administration stage. The intestinal microbiota structure of various medfly V8-GSS colonies also underwent a significant shift, despite the fact that the core microbial community was unaffected by the LEK-PC administration stage, according to 16S metagenomics sequencing. Comparison of the metabolic function prediction and associated carbohydrate enzymes among colonies treated with "LEK-PC" showed an enrichment of metabolic functions related to carbohydrates, amino acids, cofactors, and vitamins metabolism, as well as, glycoside hydrolase enzymes in the AL+ colony compared to the control. This study enriches the knowledge regarding the benefits of probiotic treatment to modulate and restore the intestinal microbiota of C. capitata sterile males for a better effectiveness of the SIT.

Latitudinal variation in survival and immature development of Ceratitis capitata populations reared in two key overwintering hosts

Ceratitis capitata, a major agricultural pest, is currently expanding its geographic distribution to northern, temperate areas of Europe. Its seasonal biology and invasion success depend on temperature, humidity and host availability. In coastal warmer Mediterranean regions and cooler temperature areas, bitter oranges and apples serve as overwintering hosts during the larval stage. We assessed the overwintering capacity of C. capitata populations obtained from different areas of the northern hemisphere by studying the survival and development rates of immature stages in both fruits under laboratory conditions. Eggs from each population were artificially inserted in the flesh of the two hosts and kept at 15, 20, or 25 °C until pupation and adult emergence. Climatic analysis of the area of the population origin showed combined effects of latitude, host and macroclimatic variables on immature survival and development rates. Egg to adult survival rates and developmental duration were longer in apples than in bitter oranges. For populations originated from southern-warmer areas, egg to adult developmental duration was prolonged and adult emergence reduced at 15 °C compared to those populations obtained from northern regions. Our findings reveal varying plastic responses of medfly populations to different overwintering hosts and temperatures highlighting the differential overwintering potential as larvae within fruits. This study contributes towards better understanding the medfly invasion dynamics in temperate areas of Northern Europe and other parts of the globe with similar climates.

Differential responses of Ceratitis capitata to infection by the entomopathogenic fungus Purpureocillium lilacinum

The medfly Ceratitis capitata is one of the most damaging fruit pests with quarantine significance due to its extremely wide host range. The use of entomopathogenic fungi constitutes a promising approach with potential applications in integrated pest management. Furthermore, developing insect control methods can involve the use of fungal machinery to cause metabolic disruption, which may increase its effectiveness by impairing insect development. Insect species, including C. capitata, relies on reproduction potential, nutrient reserves, metabolic activities, and immune response for survival. Accordingly, the purpose of this study was to investigate the impacts of the entomopathogenic fungus Purpureocillium lilacinum on C. capitata pre-mortality. The medfly V8 strain was subjected to laboratory bioassays, which consisted on determining the virulence of P. lilacinum on the medfly. Purpureocillium lilacinum was applied on abdominal topical of 5-day-old males and females. Following the fungal inoculation, we have confirmed (i) a significant increase in tissue sugar content, (ii) a significant decrease in carbohydrase activities, digestive glycosyl hydrolase, and proteinase activities in whole midguts of treated flies, (iii) the antimicrobial peptides (AMPs) genes expression profile was significantly influenced by fly gender, fly status (virgin, mature, and mated), and time after infection, but infection itself had no discernible impact on the AMPs for the genes that were examined. This study provides the first insight into how P. lilacinum could affect C. capitata physiological mechanisms and provides the foundation for considering P. lilacinum as a novel, promising biocontrol agent.

Understanding costs and benefits of thermal plasticity for pest management: insights from the integration of laboratory, semi-field and field assessments of Ceratitis capitata (Diptera: Tephritidae)

The relative costs and benefits of thermal acclimation for manipulating field performance of pest insects depend upon a number of factors including which traits are affected and how persistent any trait changes are in different environments. By assessing plastic trait responses of Ceratitis capitata (Mediterranean fruit fly) across three distinct operational environments (laboratory, semi-field, and field), we examined the influence of different thermal acclimation regimes (cool, intermediate [or handling control], and warm) on thermal tolerance traits (chill-coma recovery, heat-knockdown time, critical thermal minimum and critical thermal maximum) and flight performance (mark-release-recapture). Under laboratory conditions, thermal acclimation altered thermal limits in a relatively predictable manner and there was a generally positive effect across all traits assessed, although some traits responded more strongly. By contrast, dispersal-related performance yielded strongly contrasting results depending on the specific operational environment assessed. In semi-field conditions, warm- or cold-acclimated flies were recaptured more often than the control group at cooler ambient conditions suggesting an overall stimulatory influence of thermal variability on low-temperature dispersal. Under field conditions, a different pattern was identified: colder flies were recaptured more in warmer field conditions relative to other treatment groups. This study highlights the trait- and context-specific nature of how thermal acclimation influences traits of thermal performance and tolerance. Consequently, laboratory and semi-field assessments of dispersal may not provide results that extend into the field setting despite the apparent continuum of environmental complexity among them (laboratory < semi-field < field).

Mineral and natural films change the physical-chemical properties of grapes and modulate oviposition behaviour of Ceratitis capitata Wiedemann (Diptera: Tephritidae)

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the main pests of fruit, worldwide, and the use of population suppression method with low environmental impact is an increasingly strong requirement of the consumer market. The aim of this study was to evaluate the effect of mineral and natural films on the physical-chemical properties of grapes (Vitis vinifera L.), cultivar Itália, and oviposition behaviour of C. capitata. Fruits were immersed in suspensions (100 and 200 g L-1) of mineral (kaolin Surround®WP, kaolin 607, kaolin 608, kaolin 611 and talc) and natural films (chitosan, cassava starch, potato starch and guar gum 5.0 g L-1) and distilled water (control). After drying, fruits were exposed to C. capitata pairs of males and females for 24 h in choice and non-choice tests; the number of punctures with and without eggs, eggs per fruit and behavioural response of fly to treated and untreated fruits were recorded. Results obtained in this study are promising, given the scientific evidence that films of mineral particles such as kaolin (Surround®, 607, 608 and 611) changed the firmness, luminosity, chroma and hue angle of grapes and reduced the oviposition of C. capitata. In addition, our results also showed that natural polymers do not deter C. capitata females, but rather seem to stimulate oviposition.

Release-Recapture Test of Dispersal and Survival of Sterile Males of Ceratitis capitata (Diptera: Tephritidae)

The sterile insect technique is used around the world to suppress or eradicate populations of Ceratitis capitata (Wiedemann) with successful results. It consists of inundative releases of sterile insects into a wide area to reduce reproduction in a field population of the same species. It is necessary to know the dispersion of the sterile males in the field in order to define the maximum distance between the release points that ensures the distribution of the sterile flies in the entire target area. The release methods may vary depending on the area to be covered and the resources available. Manual ground release requires less technology. The aim of this research was to estimate the ability of sterile males to survive and disperse in the field, in the two main areas of citrus production in Uruguay. A release of 20,000 sterile males of C. capitata TslV8 (-inv D53) was performed at the central point of each area defined for the trials. Around these points, a network of 54 Jackson traps baited with trimedlure was installed forming five concentric rings, which were placed on days 1, 3, 5, and 7 after the release and were removed at 24 h in all cases. The emergence rate, flight ability, dispersion, and longevity were estimated. The standard distances obtained by the regression models were 127 m and 131 m for Salto and San José respectively. In Salto, the traps had catches until the eighth day, and in San José, there were no catches after the sixth day.

Exploring the role of host specialisation and oxidative stress in interspecific lifespan variation in subtropical tephritid flies

In herbivorous insects, the degree of host specialisation may be one ecological factor that shapes lifespan. Because host specialists can only exploit a limited number of plants, their lifecycle should be synchronised with host phenology to allow reproduction when suitable hosts are available. For species not undergoing diapause or dormancy, one strategy to achieve this could be evolving long lifespans. From a physiological perspective, oxidative stress could explain how lifespan is related to degree of host specialisation. Oxidative stress caused by Reactive Oxygen Species (ROS) might help underpin ageing (the Free Radical Theory of Aging (FRTA)) and mediate differences in lifespan. Here, we investigated how lifespan is shaped by the degree of host specialisation, phylogeny, oxidative damage accumulation and antioxidant protection in eight species of true fruit flies (Diptera: Tephritidae). We found that lifespan was not constrained by species relatedness or oxidative damage (arguing against the FRTA); nevertheless, average lifespan was positively associated with antioxidant protection. There was no lifespan difference between generalist and specialist species, but most of the tephritids studied had long lifespans in comparison with other dipterans. Long lifespan may be a trait under selection in fruit-feeding insects that do not use diapause.

Medfly-Wolbachia symbiosis: genotype x genotype interactions determine host's life history traits under mass rearing conditions

BACKGROUND

Wolbachia pipientis is a widespread, obligatory intracellular and maternally inherited bacterium, that induces a wide range of reproductive alterations to its hosts. Cytoplasmic Incompatibility (CI) is causing embryonic lethality, the most common of them. Despite that Wolbachia-borne sterility has been proposed as an environmental friendly pest control method (Incompatible Insect Technique, IIT) since 1970s, the fact that Wolbachia modifies important fitness components of its hosts sets severe barriers to IIT implementation. Mass rearing of Mediterranean fruit fly, Ceratitis capitata (medfly), is highly optimized given that this pest is a model species regarding the implementation of another sterility based pest control method, the Sterile Insect Technique (SIT). We used the medfly-Wolbachia symbiotic association, as a model system, to study the effect of two different Wolbachia strains, on the life history traits of 2 C. capitata lines with different genomic background.

RESULTS

Wolbachia effects are regulated by both C. capitata genetic background and the Wolbachia strain. Wolbachia infection reduces fertility rates in both C. capitata genetic backgrounds and shortens the pre-pupa developmental duration in the GSS strain. On the other hand, regardless of the strain of Wolbachia (wCer2, wCer4) infection does not affect either the sex ratio or the longevity of adults. wCer4 infection imposed a reduction in females' fecundity but wCer2 did not. Male mating competitiveness, adults flight ability and longevity under water and food deprivation were affected by both the genetic background of medfly and the strain of Wolbachia (genotype by genotype interaction).

CONCLUSION

Wolbachia infection could alter important life history traits of mass-reared C. capitata lines and therefore the response of each genotype on the Wolbachia infection should be considered toward ensuring the productivity of the Wolbachia-infected insects under mass-rearing conditions.

Effects of early-life protein starvation on longevity and sexual performance of male medfly

Using a well-established model species for demographic, behavioural and aging research, the Mediterranean fruit fly (Ceratitis capitata), we explored whether nutritional stress early in adult life affects the sexual performance and survival in older ages. To do so we established two different protein starvation (PS) protocols that included the elimination of proteinaceous diet either before or after sexual maturity of male medflies. The frequency of sexual signalling and the age of death were daily recorded. Sexual signalling is directly related with male mating success in this model system. PS early in adult life results in high mortality rates (similar to sugar-only fed males), which are gradually restored in more advanced ages. Provision of a proteinaceous diet following early-life PS increases straightaway male sexual signalling to levels similar with those having continuous access to proteinaceous diet. Switching diet regimes from a protein-free to a protein-rich one progressively compensates mortality rates. Apparently, males prioritize sexual signalling over lifespan. PS after attaining sexual maturity significantly reduces both longevity and sexual performance. Access to protein only early in life is insufficient to support lifetime energy-consuming behaviours such as sexual signalling. Continuous access to a proteinaceous diet determines both lifetime sexual performance and longevity. Early in life PS males prioritize the allocation of nutritional elements, when available, in sexual activities over soma-maintenance.

Laboratory Evaluation of Natural and Synthetic Aromatic Compounds as Potential Attractants for Male Mediterranean fruit Fly, Ceratitis capitata

Ceratitis capitata, the Mediterranean fruit fly, is one of the most serious agricultural pests worldwide responsible for significant reduction in fruit and vegetable yields. Eradication is expensive and often not feasible. Current control methods include the application of conventional insecticides, leading to pesticide resistance and unwanted environmental effects. The aim of this study was to identify potential new attractants for incorporation into more environmentally sound management programs for C. capitata. In initial binary choice bioassays against control, a series of naturally occurring plant and fungal aromatic compounds and their related analogs were screened, identifying phenyllactic acid (7), estragole (24), o-eugenol (21), and 2-allylphenol (23) as promising attractants for male C. capitata. Subsequent binary choice tests evaluated five semisynthetic derivatives prepared from 2-allylphenol, but none of these were as attractive as 2-allylphenol. In binary choice bioassays with the four most attractive compounds, males were more attracted to o-eugenol (21) than to estragole (24), 2-allylphenol (23), or phenyllactic acid (7). In addition, electroantennography (EAG) was used to quantify antennal olfactory responses to the individual compounds (1–29), and the strongest EAG responses were elicited by 1-allyl-4-(trifluoromethyl)benzene (11), estragole (24), 4-allyltoluene (14), trans-anethole (9), o-eugenol (21), and 2-allylphenol (23). The compounds evaluated in the current investigation provide insight into chemical structure–function relationships and help direct future efforts in the development of improved attractants for the detection and control of invasive C. capitata.

Structural and biochemical evaluation of Ceratitis capitata odorant-binding protein 22 affinity for odorants involved in intersex communication

In insects, odorant-binding proteins (OBPs) connect the peripheral sensory system to receptors of olfactory organs. Medfly Ceratitis capitata CcapObp22 shows 37% identity and close phylogenetic affinities with Drosophila melanogaster OBP69a/pheromone-binding protein related protein 1. The CcapObp22 gene is transcribed in the antennae and maxillary palps, suggesting an active role in olfaction. Here, we recombinantly produced CcapObp22, obtaining a 13.5 kDa protein capable of binding multiple strongly hydrophobic terpene compounds, including medfly male pheromone components. The highest binding affinity [half maximal effective concentration (EC50) = 0.48 µM] was to (E,E)-α-farnesene, one of the most abundant compounds in the male pheromone blend. This odorant was used in cocrystallization experiments, yielding the structure of CcapOBP22. The monomeric structure shows the typical OBP folding, constituted by six α-helical elements interconnected by three disulphide bridges. A C-terminal seventh α-helix constitutes the wall of a deep, L-shaped hydrophobic cavity. Analysis of the electron density in this cavity suggested trapping of farnesene in the crystal structure, although with partial occupancy. Superposition of the CcapOBP22 structure with related seven-helical OBPs highlights striking similarity in the organization of the C-terminal segment of these proteins. Collectively, our molecular and physiological data on medfly CcapOBP22 suggest its involvement in intersex olfactory communication.

Quantification of dose-mortality responses in adult Diptera: Validation using Ceratitis capitata and Drosophila suzukii responses to spinosad

Quantitative laboratory bioassay methods are required to evaluate the toxicity of novel insecticidal compounds for pest control and to determine the presence of resistance traits. We used a radioactive tracer based on ³²P-ATP to estimate the volume of a droplet ingested by two dipteran pests: Ceratitis capitata (Tephritidae) and Drosophila suzukii (Drosophilidae). Using blue food dye it was possible to distinguish between individuals that ingested the solution from those that did not. The average volume ingested by C. capitata adults was 1.968 μl. Females ingested a ~20% greater volume of solution than males. Adults of D. suzukii ingested an average of 0.879 μl and females ingested ~30% greater volume than males. The droplet feeding method was validated using the naturally-derived insecticide spinosad as the active ingredient (a.i.). For C. capitata, the concentration-mortality response did not differ between the sexes or among three different batches of insects. Lethal dose values were calculated based on mean ingested volumes. For C. capitata LD₅₀ values were 1.462 and 1.502 ng a.i./insect for males and females, respectively, equivalent to 0.274 and 0.271 ng a.i./mg for males and females, respectively, when sex-specific variation in body weight was considered. Using the same process for D. suzukii, the LD₅₀ value was estimated at 2.927 ng a.i./insect, or 1.994 ng a.i./mg based on a mean body weight of 1.67 mg for both sexes together. We conclude that this technique could be readily employed for determination of the resistance status and dose-mortality responses of insecticidal compounds in many species of pestiferous Diptera.

Contribution of maternal effects to dietary selection in Mediterranean fruit flies

Individual responses to dietary variation represent a fundamental component of fitness, and nutritional adaptation can occur over just a few generations. Maternal effects can show marked proximate responses to nutrition, but whether they contribute to longer term dietary adaptation is unclear. Here, we tested the hypotheses that maternal effects: (i) contribute to dietary adaptation, (ii) diminish when dietary conditions are constant between generations, (iii) are trait-specific and (iv) interact with high- and low-quality food. We used experimental evolution regimes in the medfly (Ceratitis capitata) to test these predictions by subjecting an outbred laboratory-adapted population to replicated experimental evolution on either constant high calorie sugar ('A') or low-calorie starch ('S') larval diets, with a standard adult diet across both regimes. We measured the contribution of maternal effects by comparing developmental and adult phenotypes of individuals reared on their own diet with those swapped onto the opposite diet for either one or two generations (high and low maternal effect conditions, respectively), both at the start and after 30 generations of selection. Initially, there were strong maternal effects on female body mass and male mating success but not larval survival. Interestingly, the initial maternal effects observed in female body mass and male mating success showed sex-specific interactions when individuals from high calorie regimes were tested on low calorie diets. However, as populations responded to selection, the effects of maternal provisioning on all traits diminished. The results broadly supported the predictions. They show how the contribution of maternal effects to dietary responses evolves in a context-dependent manner, with significant variation across different fitness-related traits. We conclude that maternal effects can evolve during nutritional adaptation and hence may be an important life history trait to measure, rather than to routinely minimize.

Cryopreservation of the Mediterranean fruit fly (Diptera: Tephritidae) VIENNA 8 genetic sexing strain: No effect on large scale production of high quality sterile males for SIT applications

The sterile insect technique (SIT) integrated in area-wide integrated pest management (AW-IPM) programmes is being used for the successful management of the Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) which is a horticultural pest of economic importance in tropical and subtropical countries. All programmes with an SIT component are using the VIENNA genetic sexing strains (GSS), mainly the VIENNA 8 GSS, which have been developed by applying classical genetic approaches. The VIENNA 8 GSS carries two selectable markers, the white pupae and the temperature sensitive lethal genes, which allows the production and release of only males thus increasing the biological efficiency and cost effectiveness of SIT applications. However, mass rearing may affect quality traits of the GSS, in which case replenishment of the colony with wild flies is recommended, a process which is tedious and time consuming. We previously reported the development of a cryopreservation protocol for the VIENNA 8^D53+ strain. In the present study, we report on the evaluation of the cryopreserved strain VIENNA 8^D53+/Cryo-228L, reared under semi mass rearing conditions, for production parameters, quality control indices and mating competitiveness of males, in a comparative way with the non-cryopreserved VIENNA 8^D53+ strain, against wild type males. The VIENNA 8^D53+ and VIENNA 8^D53+/Cryo-228L strains were similar for production parameters viz. egg production, pupal production, pupal recovery, and quality control indices like fly emergence, sex ratio and flight ability. Males from both strains were equally competitive with males of the wild type strain in achieving mating with wild type females under field cage conditions. Results are discussed in the context of cryopreservation as a potential backup strategy for refreshing the mass rearing colony with biological material from a cryopreserved stock.

Oviposition preference of Ceratitis capitata (Diptera: Tephritidae) at different times after pruning 'Italia' table grapes grown in Brazil

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.

Evaluation of the attractant effect and lipid profile modulation of natural fixed oils on the medfly Ceratitis capitata (Wiedemann)

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann, 1824; Diptera: Tephritidae), is a polyphagous pest in horticulture, mainly targeting Citrus fruits. Natural essential and fixed oils are currently under investigation for their broad-spectrum in pest control. To gain better knowledge about medfly behavior and biochemistry, we examined with behavioral and biochemical assays, the effects on C. capitata from six natural fixed oils obtained from vegetable (five) or animal (one) matrices using the eco-friendly supercritical CO ₂ extraction. Oils were obtained at 250/300 bar and 40°C from the seeds of Laurus nobilis and Citrus paradisi, the fruits of Myristica fragrans and Pistacia terebinthus, wheat germ, and mullet roes (marine oil). Behavioral experiments were performed by means of two-choice tests to analyze the oil attractant effect compared with control (water or standard diet). The fatty acid composition of oils and the total lipid and fatty acid profile of medflies were characterized by chromatographic techniques. Behavioral bioassays showed that fixed oil obtained from M. fragrans (nutmeg butter) was more attractive than other oils. Medflies fed (24 hr) on marine oil showed significant changes in the total lipid and fatty acid profile induced by oil ingestion without toxic effects. However, 56% mortality was observed in insects fed on M. fragrans oil and no biochemical changes ascribable to oil ingestion were detected in the medflies that survived. Our results advance knowledge about the behavioral and biochemical response of medflies to fixed oils and will be potentially useful in developing new pest management strategies.

Olfactory sensitivity to major, intermediate and trace components of sex pheromone in Ceratitis capitata is related to mating and circadian rhythm

The Mediterranean fruit fly, Ceratitis capitata Wied., is a worldwide pest of several fruits given its extremely wide host range which includes more than 250 different species of fruits and vegetables. Its high biological potential is mainly due both to its ability to readily adapt to new environments and its high reproductive capacity as it completes multiple generations each year. Since sexually mature males emit a sex pheromone to call both other males for "lekking" and receptive females for mating, many studies have been directed to characterize the chemical composition of the sex pheromone. Besides, the release of sex pheromone appears to be modulated both by mating and time of day. Based on these considerations, we measured the olfactory sensitivity of antennae and palps of C. capitata to six volatiles of the male sex-pheromone: α-farnesene and geranyl acetate (major components), linalool and β-myrcene (intermediate components), β-farnesene and 2,3-butanediol (minor/trace components). The electroantennogram (EAG) and electropalpogram (EPG) responses were evaluated in both sexes, at different physiological states (virgin and mated), and at different times of the day (morning and afternoon). The results show that the EAG amplitude values in response to all stimuli are higher in the morning than in the afternoon for both sexes and in both virgin and mated insects. Furthermore, in both sexes, the olfactory sensitivity of virgin insects is higher than in mated ones. The EPG amplitude in response to all stimuli is higher in the morning in mated females than in virgin females and higher in the morning than in the afternoon in both mated sexes. By gaining knowledge on the effects of sex, physiological state and time of day on the olfactory sensitivity of C. capitata, one could better understand the medfly reproductive behavior.

Evaluation of Providencia rettgeri pathogenicity against laboratory Mediterranean fruit fly strain (Ceratitis capitata)

The Mediterranean fruit fly (medfly) Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is often referred to as the most severe agricultural pest. Its biological control is mainly through the Sterile Insect Technique (SIT). Colonization, mass-rearing conditions and the irradiation process impact the competitiveness of sterile males and disrupt symbiotic associations by favoring some bacterial species and suppressing others. Levels of Providencia species have been shown to fluctuate considerably in the gut of the medfly laboratory strain Vienna 8 under irradiation, increasing by up to 22%. This study aimed to determine the pathogenicity of Providencia rettgeri isolated from the gut of laboratory Vienna 8 medfly strains by examining the effects of 1) two different treatment doses on egg-hatching and development and 2) two infection methodologies (ingestion and injection) of male and female adults according to their mating status. Treatment of eggs with P. rettgeri (2%) significantly decreased the mean egg to pupae recovery rate. Our data showed significant high mortality in flies with both injection and ingestion after 24 hours without any effect of sex. Microbial counts demonstrated that the bacteria could proliferate and replicate in adult flies. There was a significant sex-dependent effect after infection, with mortality decreasing significantly for males more than females. Providencia rettgeri can be considered as a potential pathogen of C. capitata. Mating protected males and females against infection by P. rettgeri by triggering an immune response leading to double the levels of Cecropin being secreted compared to infected virgin adults, thus reducing the virulence of the bacteria.

Extracellular activity of NBAD-synthase is responsible for colouration of brown spots in Ceratitis capitata wings

After the emergence of the Ceratitis capitata imago, the pale and folded wings are expanded and sclerotized to acquire the definitive form and to stabilize the cuticle. The wings of this fly show a specific pattern of brownish and black spots. Black spots are pigmented by melanin, whereas there was scarce information about the development of the brownish spots. N-beta-alanydopamine (NBAD) is the main tanning precursor in C. capitata body cuticle, and we hypothesized that it may be responsible for the colouration of the brownish spots. We determined the topology and timing of NBAD synthesis and deposition to attain the species-specific colouration pattern. We demonstrated that during the first hours the colour of the brownish spots was principally determined by the tanning of the hairs. Haemolymph circulation through the veins is required to tan the wings. We confirmed that soon after wing spreading, most of the wing epidermal cells disappeared. Thus, the tanning of the brown spots was accomplished when the wing lamina was devoid of cells. NBAD synthase (NBAD-S; Ebony protein in D. melanogaster) activity in wings was detected in pharate adults and lasted several days after the emergence, even after the end of the tanning process. This observation is in contrast to epidermal NBAD-S activity in the body, where it was nearly undetectable 48 h post emergence. Our results indicate that NBAD-S was exported and deposited into the extracellular matrix of the brown spot areas before cell death and that tanning occurs through gradual export of NBAD precursors (dopamine and b-alanine) from veins.

Identification of Ceratitis capitata (Diptera: Tephritidae) Sperm From Females in Traps: The Importance of the Ventral Receptacle

The monitoring of a pest population often relies on the identification of individuals from traps. For area-wide programs utilizing the sterile insect technique, the further identification of the mated status of females found in traps is of utmost importance. For the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), this is usually verified through the assessment of sperm in the spermathecae. However, this can be misleading for species where there are other sperm storage organs such as the ventral receptacle. Here, we studied the relative importance of sperm storage in the ventral receptacle compared to the spermathecae for females from 5 to 18 d of age. Furthermore, we studied how sperm can be identified in the ventral receptacle or spermathecae after females were recovered from traps. We found no effect of female age on likelihood of sperm storage. Sperm could be identified in both sperm storage organs at 7 or 14 d after females had been placed in traps. We found that the ventral receptacle is a more reliable indicator of female mated status. Thus, we propose that if no sperm are found in the spermathecae, program managers should revise the ventral receptacle before assuming that females are not mated. This test may also be relevant to other pest tephritids that store even more sperm in the ventral receptacle than C. capitata.

Revised Distribution of Bactrocera tryoni in Eastern Australia and Effect on Possible Incursions of Mediterranean Fruit Fly: Development of Australia's Eastern Trading Block

Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), commonly called 'Queensland fruit fly' in Australia, and Mediterranean fruit fly (Ceratitis capitata Wiedemann) (Diptera: Tephritidae) are the two most economically important fruit fly in Australia with B. tryoni in the east and Mediterranean fruit fly in the west. The two species coexisted for several decades, but it is believed that B. tryoni displaced Mediterranean fruit fly. In southeastern Australia, this was deemed inadequate for export market access, and a large fruit fly free zone (fruit fly exclusion zone) was developed in 1996 where B. tryoni was eradicated by each state department in their portion of the zone. This zone caused an artificial restricted distribution of B. tryoni. When the fruit fly exclusion zone was withdrawn in Victoria and New South Wales in 2013, B. tryoni became endemic once again in this area and the national distribution of B. tryoni changed. For export markets, B. tryoni is now deemed endemic to all eastern Australian states, except for the Greater Sunraysia Pest-Free Area. All regulatory controls have been removed between eastern states, except for some small zones, subject to domestic market access requirements. The eastern Australian states now form a B. tryoni endemic trading group or block. All Australian states and territories maintain legislation to regulate the movement of potentially infested host fruit into their states. In particular, eastern states remain active and regulate the entry of commodities possibly infested with Mediterranean fruit fly. The combination of regulatory controls limits the chances of Mediterranean fruit fly entering eastern states, and if it did, Mediterranean fruit fly is unlikely to establish in the opposition to a well-established B. tryoni population.

Towards improving sterile insect technique: Exposure to orange oil compounds increases sexual signalling and longevity in Ceratitis capitata males of the Vienna 8 GSS

The Mediterranean fruit fly (medfly), Ceratitis capitata, is a notorious insect pest causing huge economic losses worldwide. The sterile insect technique (SIT) is widely used for its control. Using sexually mature sterilized males of the Vienna 8 (tsl) strain in the laboratory, we explored whether exposure of males to citrus compounds (separately or in a mixture) affects their sexual behaviour and if nutritional conditions and age modulate those effects. Exposed males exhibited increased sexual signalling compared to unexposed ones, particularly when fed a rich adult diet. Interestingly, and for the first time reported in medfly, exposure of Vienna 8 males to a mixture of citrus compounds increases longevity under poor adult diet conditions. We discuss the possible associated mechanisms and provide some practical implications of our results towards improving the effectiveness of SIT.

Chemical Degradation of TMR Multilure Dispensers for Fruit Fly Detection Weathered Under California Climatic Conditions

Degradation models for multilure fruit fly trap dispensers were analyzed to determine their potential for use in large California detection programs. Solid three-component male lure TMR (trimedlure [TML], methyl eugenol [ME], raspberry ketone [RK]) dispensers impregnated with DDVP (2, 2-dichlorovinyl dimethyl phosphate) insecticide placed inside Jackson traps were weathered during summer (8 wk) and winter (12 wk) in five citrus-growing areas. Additionally, TMR wafers without DDVP, but with an insecticidal strip, were compared to TMR dispensers with DDVP. Weathered dispensers were sampled weekly and chemically analyzed. Percent loss of TML, the male lure for Ceratitis capitata (Wiedemann) Mediterranean fruit fly; ME, the male lure for Bactrocera dorsalis (Hendel), oriental fruit fly; RK, the male lure for Bactrocera cucurbitae (Coquillett), melon fly; and DDVP was measured. Based on regression analyses for the male lures, TML degraded the fastest followed by ME. Degradation of the more chemically stable RK was discontinuous, did not fit a regression model, but followed similar seasonal patterns. There were few location differences for all three male lures and DDVP. Dispensers degraded faster during summer than winter. An asymptotic regression model provided a good fit for % loss (ME, TML, and DDVP) for summer data. Degradation of DDVP in TMR dispensers was similar to degradation of DDVP in insecticidal strips. Based on these chemical analyses and prior bioassay results with wild flies, TMR dispensers could potentially be used in place of three individual male lure traps, reducing costs of fruit fly survey programs. Use of an insecticidal tape would not require TMR dispensers without DDVP to be registered with US-EPA.

Effect of Irradiation Doses on Sterility and Biological Security in a Genetically Modified Strain of the Mediterranean Fruit Fly (Diptera: Tephritidae)

The genetically modified strain of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) VIENNA 8 1260, was developed from the genetic sexing strain VIENNA 8. It has two molecular markers that exhibit red fluorescence in the body and green fluorescence in testis and sperm. These traits offer a precise tool to discriminate between mass-reared and wild males, increasing the effectiveness of sterile insect technique. The reproductive performance of the VIENNA 8 1260 and VIENNA 8 D53- (without the D53 inversion introduced to prevent recombination) was compared at different irradiation doses. The general effect of irradiation on VIENNA 8 1260 followed the same patterns documented in previous publications for VIENNA 8 D53-. Irradiation doses of 80 Gray or greater reduced fertility and induced high levels of sterility in wild females. Fecundity reduction was higher in VIENNA 8 1260 than in VIENNA 8 D53- females. Vertical transmission of the fluorescence gene was confirmed up to the F4 generation. Substerilization in the VIENNA 8 1260 could jeopardize the usefulness of the transgenic strain due to the possible vertical transfer of the fluorescence transgene from the sterile males to the wild flies. A biologically safe higher irradiation dose could result in reduced competitiveness of the VIENNA 8 1260 strain. Mating and remating experiments suggest that Mediterranean fruit fly females exhibit a relative precedence in the use of the sperm: though both sperms are mixed, sperm from the remating is spent first. Results suggest a lower fitness of VIENNA 8 1260 sperm, when compared with sperm from a nonfluorescent bisexual strain, which is consistent with the lower reproductive performance documented for the VIENNA 8 1260 strain.

Cold Disinfestation of "Hass" Avocado (Persia americana) of Three Species of Fruit Fly (Diptera: Tephritidae)-Ceratitis capitata, Ceratitis rosa, and Ceratitis cosyra

The avocado industry is important in South Africa, but access to certain markets is impeded by the presence of phytosanitary pests. One of the ways of securing entry to these markets is to demonstrate that a mitigating treatment will result in there being a negligible chance of accidental importation. In cold treatment comparative studies at 0 °C and 2 °C of immature stages of Ceratitis capitata (Wiedemann), Ceratitis rosa Karsch, and Ceratitis cosyra (Walker) in "Hass" avocado, the third instar of C. cosyra was shown to be the most cold tolerant. This larval life stage was used in a large-scale trial to test treatment efficacy at 2 °C, a temperature known to be the better for fruit quality. There were no survivors from the 49,795 individual fruit fly larvae subjected to the cold treatment at 2 °C for 20 d. It is argued that, although this level of assessment falls short of the Probit 9 level normally required for fruit fly, they are rarely found in avocado fruit and that the level of disinfestation obtained is more than sufficient to achieve quarantine security.

Interspecific Competition Between Ceratitis capitata and Two Bactrocera Spp. (Diptera: Tephritidae) Evaluated via Adult Behavioral Interference Under Laboratory Conditions

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is considered one of the most invasive tephritid species. It has spread and established populations successfully throughout many of the tropical temperate regions, partially owing to the increase in global trading activity that facilitates diffusion of species. However, C. capitata has never been detected in China, even though some areas of the country have favorable climate and ample food resources. Historically, some researchers have hypothesized that the principal reasons for its absence are the defenses mounted by native Bactrocera species against C. capitata. We evaluated the modes and strengths of interspecific competition between C. capitata and two Bactrocera species (Bactrocera dorsalis Hendel and Bactrocera correcta Bezzi) by conducting experiments on behavioral interference between the adults of these fruit fly species. Under appropriate conditions, the two Bactrocera species showed a distinct advantage in competition for oviposition, noticeably suppressing C. capitata. Although no mating interference between C. capitata and the two Bactrocera species was observed, the role of interference competition in the prevention of C. capitata invasion is still worthy of being discussed.

Toxic and hormetic-like effects of three components of citrus essential oils on adult Mediterranean fruit flies (Ceratitis capitata)

Plant essential oils (EOs) and a wide range of their individual components are involved in a variety of biological interactions with insect pests including stimulatory, deterrent, toxic and even hormetic effects. Both the beneficial and toxic properties of citrus EOs on the Mediterranean fruit fly (medfly) have been experimentally evidenced over the last years. However, no information is available regarding the toxic or beneficial effects of the major components of citrus EOs via contact with the adults of the Mediterranean fruit fly. In the present study, we explored the toxicity of limonene, linalool and α-pinene (3 of the main compounds of citrus EOs) against adult medflies and identified the effects of sub-lethal doses of limonene on fitness traits in a relaxed [full diet (yeast and sugar)] and in a stressful (sugar only) feeding environment. Our results demonstrate that all three compounds inferred high toxicity to adult medflies regardless of the diet, with males being more sensitive than females. Sub-lethal doses of limonene (LD₂₀) enhanced the lifespan of adult medflies when they were deprived of protein. Fecundity was positively affected when females were exposed to limonene sub-lethal doses. Therefore, limonene, a major constituent of citrus EOs, induces high mortality at increased doses and positive effects on life history traits of medfly adults through contact at low sub-lethal doses. A hormetic-like effect of limonene to adult medflies and its possible underlying mechanisms are discussed.

An Additional Phytosanitary Cold Treatment Against Ceratitis capitata (Diptera: Tephritidae) in 'Oroblanco' Citrus Fruit

For 'Oroblanco' ('Sweetie'), the sweet seedless pummelo-grapefruit hybrid, when exported from Israel to Japan, the standard cold treatment against Ceratitis capitata (Wied.) (Diptera: Tephritidae) is conducted at ≤ 1.5 °C, for 16 d. In recent years, the transportation means of exported citrus was changed from reefer vessels to individual refrigerated containers, where the fruit bulk is relatively small and may be exposed to temperature fluctuations and to the risk of chilling injuries. To reduce this risk, Israel proposed to Japan to increase the treatment temperature and extend its duration to 2.2 °C and 18 d, respectively. This study shows that the proposed treatment effectively kills the third instar larva of C. capitata, in Oroblanco.

Adaptation to divergent larval diets in the medfly, Ceratitis capitata

Variation in diet can influence the timing of major life-history events and can drive population diversification and ultimately speciation. Proximate responses of life histories to diet have been well studied. However, there are scant experimental data on how organisms adapt to divergent diets over the longer term. We focused on this omission by testing the responses of a global pest, the Mediterranean fruitfly, to divergent selection on larval diets of different nutritional profiles. Tests conducted before and after 30 generations of nutritional selection revealed a complex interplay between the effects of novel larval dietary conditions on both plastic and evolved responses. There were proximate-only responses to the larval diet in adult male courtship and the frequency of copulation. Males on higher calorie larval diets consistently engaged in more bouts of energetic courtship. In contrast, following selection, larval development time, and egg to adult survival showed evidence of evolved divergence between diet regimes. Adult body size showed evidence for adaptation, with flies being significantly heavier when reared on their "own" diet. The results show the multifaceted responses of individuals to dietary selection and are important in understanding the extreme generalism exhibited by the medfly.

Performance of a Genetically Modified Strain of the Mediterranean Fruit Fly (Diptera: Tephritidae) for Area-Wide Integrated Pest Management With the Sterile Insect Technique

The genetically modified strain of Ceratitis capitata (Wiedemann) VIENNA 8 1260 has two morphological markers that exhibit fluorescence in body and sperm. To assess the feasibility of its use in area-wide integrated pest management (AW-IPM) programs using the sterile insect technique, its rearing performance and quality control profile under small, medium, and large scales was evaluated, as well as in field cages. The VIENNA 8 1260 strain had a lower yield than the control strains, VIENNA 8 with D53 inversion (VIENNA 8) and without D53 inversion (VIENNA 8 D53-). At mass-rearing scale, yield gradually increased in three generations without reaching the control strain values. The VIENNA 8 1260 strain was stable in the genetic sexing mechanism (>99.9%) and expression of fluorescence (100%). In field cages, the VIENNA 8 1260 males reduced the mating potential of wild males in the same magnitude as the VIENNA 8, when evaluated in independent cage tests. However, the relative sterility index and the strain male relative performance index of VIENNA 8 1260 males were significantly lower than those of the VIENNA 8. There were no significant differences in longevity of these strains. The potential application of the VIENNA 8 1260 in AW-IPM programs is further discussed.

Seasonality of the Mediterranean Fruit Fly (Diptera: Tephritidae) on Terceira and Sao Jorge Islands, Azores, Portugal

Population dynamics studies are very important for any area-wide control program as they provide detailed knowledge about the relationship of Medfly [Ceratitis capitata (Wiedemann)] life cycle with host availability and abundance. The main goal of this study is to analyse seasonality of C. capitata in Terceira and Sao Jorge Islands (Azores archipelago) using field and laboratory data collected during (2010-2014) CABMEDMAC (MAC/3/A163) project. The results from Sao Jorge Island indicate significantly lower male/female ratio than on Terceira Island. This is an important finding specially regarding when stablishing the scenario parameters for a sterile insect technique application in each island. The population dynamics of C. capitata are generally linked with host fruit availability and abundance. However, on Terceira Island fruit infestation levels are not synchronized with the trap counts. For example, there was Medfly infestations in some fruits [e.g., Solanum mauritianum (Scop.)] while in the nearby traps there were no captures at the same time. From this perspective, it is important to denote the importance of wild invasive plants, on the population dynamics of C. capitata, as well important to consider the possibility of having different densities of traps according to the characteristics of each area in order to improve the network of traps surveillance's sensitivity on Terceira Island.

Stage and cell-specific expression and intracellular localization of the small heat shock protein Hsp27 during oogenesis and spermatogenesis in the Mediterranean fruit fly, Ceratitis capitata

The cell-specific expression and intracellular distribution of the small heat protein Hsp27 was investigated in the ovaries and testes of the Mediterranean fruit fly, Ceratitis capitata (medfly), under both normal and heat shock conditions. For this study, a gfp-hsp27 strain was used to detect the chimeric protein by confocal microscopy. In unstressed ovaries, the protein was expressed throughout egg development in a stage and cell-specific pattern. In germarium, the protein was detected in the cytoplasm of the somatic cells in both unstressed and heat-shocked ovaries. In the early stages of oogenesis of unstressed ovaries, the protein was mainly located in the perinuclear region of the germ cells and in the cytoplasm of the follicle cells, while in later stages (9-10) it was distributed in the cytoplasm of the germ cells. In late stages (12-14), the protein changed localization pattern and was exclusively associated with the nuclei of the somatic cells. In heat shocked ovaries, the protein was mainly located in the nuclei of the somatic cells throughout egg chamber's development. In unstressed testes, the chimeric protein was detected in the nuclei of primary spermatocytes and in the filamentous structures of spermatid bundles, called actin cones. Interestingly, after a heat shock, the protein presented the same cell-specific localization pattern as in unstressed testes. Furthermore, the protein was also detected in the nuclei of the epithelial cells of the deferent duct, the accessory glands and the ejaculatory bulb. Our data suggest that medfly Hsp27 may have cell-specific functions, especially in the nucleus. Moreover, the association of this protein to actin cones during spermatid individualization, suggests a possible role of the protein in the formation and stabilization of actin cones.

Sperm-less males modulate female behaviour in Ceratitis capitata (Diptera: Tephritidae)

In the Mediterranean fruit fly, Ceratitis capitata (Wiedemann)(Diptera: Tephritidae), mating has a strong impact on female biology, leading to a decrease in sexual receptivity and increased oviposition and fecundity. Previous studies suggest that sperm transfer may play a role in inducing these behavioural changes. Here we report the identification of a medfly innexin gene, Cc-inx5, whose expression is limited to the germ-line of both sexes. Through RNA interference of this gene, we generated males without testes and, consequently, sperm, but apparently retaining all the other reproductive organs intact. These sperm-less males were able to mate and, like their wild-type counterparts, to induce in their partners increased oviposition rates and refractoriness to remating. Interestingly, matings to sperm-less males results in oviposition rates higher than those induced by copulation with control males. In addition, the observed female post-mating behavioural changes were congruent with changes in transcript abundance of genes known to be regulated by mating in this species. Our results suggest that sperm transfer is not necessary to reduce female sexual receptivity and to increase oviposition and fecundity. These data pave the way to a better understanding of the role/s of seminal components in modulating female post-mating responses. In the long term, this knowledge will be the basis for the development of novel approaches for the manipulation of female fertility, and, consequently, innovative tools to be applied to medfly control strategies in the field.

Population Fluctuation of Ceratitis capitata (Diptera: Tephritidae) as a Function of Altitude in Eastern Guatemala

Population fluctuations of Ceratitis capitata (Wiedemann) were evaluated over a period of 12 mo in four altitudinal strata (400-750, 750-1,100, 1,100-1,450, and 1,450-1,800 meters above sea level, masl) in Eastern Guatemala. Within each altitudinal range, sampling plots were established in coffee plantations and adjacent areas, in which Jackson traps were set and baited with Trimedlure. Coffee berries and other host fruits were collected. Population density was lowest at the 400-750 masl stratum and highest at 1,450-1,800 masl. At every altitudinal range, the fluctuations of the pest were associated mainly with the availability of ripe coffee berries as a primary host. From 750-1,450 masl, the pest was also associated with the availability of sweet orange and mandarins in commercial and backyard orchards. The highest densities of the pest were recorded in the dry season. Citrus were the main alternate host where ripe coffee berries were not available. This knowledge on population dynamics of C. capitata will contribute to develop more effective area-wide pest management strategies including the use of sterile insects, natural enemies, and bait sprays.

Field Efficacy of a Metarhizium anisopliae-Based Attractant-Contaminant Device to Control Ceratitis capitata (Diptera: Tephritidae)

Biological control of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) using entomopathogenic fungi is being studied as a viable control strategy. The efficacy of a Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae)-based attractant-contaminant device (ACD) to control C. capitata was evaluated in a medium-scale (40 ha) 2-yr field trial using a density of 24 ACD per ha. Results showed that this density was adequate to efficiently reduce fruitfly populations and that the inoculation dishes (IDs) needed replacing mid-season to provide protection for the entire season. In this study, fungal treatment was even more effective than conventional chemical treatment. Population dynamics in fungus-treated fields along with the infectivity study of field-aged IDs in the laboratory found that the ACD remained effective for at least 3 mo. The results suggest M. anisopliae-based ACD can be used to control C. capitata in the field. The implications of its use, especially as a tool in an integrated pest management program, are discussed.

Temporal Overlap and Co-Occurrence in a Guild of Sub-Tropical Tephritid Fruit Flies

Studies of community assembly have emphasized snapshot comparisons of spatially replicated samples from "natural" assemblages. Agro-ecosystems are characterized by relatively little habitat heterogeneity and no dispersal barriers for actively flying insects. Therefore, dynamic patterns of species segregation and aggregation are more likely to reflect the direct or indirect effects of species interactions. We studied the temporal organization of a guild of 21 congeneric species of Anastrepha that colonized fruit orchards in Monte Alegre do Sul, São Paulo, Brazil. This assemblage also included the introduced Mediterranean fruit fly Ceratitis capitata. One hundred six consecutive weekly censuses (11 Jan 2002-16 Jan 2004) of flies in guava, loquat, and peach orchards revealed a pattern of minimum abundance during the coldest months of each year (June and July) and a maximum abundance during periods of flowering and fruit ripening. Overall, phenological overlap was greater than expected by chance. However, conditioned on the pattern of seasonal abundances, temporal occurrence and abundance matrices exhibited patterns of significant species segregation and anti-nestedness. In each year, the 3 orchards contained a small number of species pairs that exhibited statistically significant temporal segregation or aggregation. Most aggregated and segregated pairs reflected seasonal shifts in species presences that were not related to variation in air temperature. Most of the significant pairwise associations involved C. capitata: 8 of the 11 segregated pairs and 2 of the 7 aggregated pairs. These results suggest that species interactions between introduced and native species can be an important determinant of species associations in agro-ecosystems.

Field Estimates of Attraction of Ceratitis capitata to Trimedlure and Bactrocera dorsalis (Diptera: Tephritidae) to Methyl Eugenol in Varying Environments

Measuring and modeling the attractiveness of semiochemical-baited traps is of significant importance to detection, delimitation, and control of invasive pests. Here, we describe the results of field mark-release-recapture experiments with Ceratitis capitata (Wiedemann) and Bactrocera dorsalis (Hendel) to estimate the relationship between distance from a trap baited with trimedlure and methyl eugenol, respectively, and probability of capture for a receptive male insect. Experiments were conducted using a grid of traps with a central release point at two sites on Hawaii Island, a Macadamia orchard on the East side of the island and a lava field on the West side. We found that for B. dorsalis and methyl eugenol there is a 65% probability of capture at ∼36 m from a single trap, regardless of habitat. For C. capitata, we found a 65% probability of capture at a distance of ∼14 m from a single trap in the orchard and 7 m in the lava field. We also present results on the spatial and temporal pattern of recaptures. The attraction data are analyzed via a hyperbolic secant-based capture probability model.

Analysis of survival, gene expression and behavior following chill-coma in the medfly Ceratitis capitata: effects of population heterogeneity and age

The medfly Ceratitis capitata is an agricultural pest distributed worldwide thanks, in part, to its phenotypic plasticity of thermal tolerance. Cold exposure has been shown to reduce C. capitata survival, which may affect its distribution in areas with subfreezing temperatures. When insects are increasingly cooled, they attain a critical thermal threshold and enter a chill-coma state characterized by cessation of movement. It is not clear how a rapid cold exposure affects the physiological state of medflies, and how this is influenced by age and population heterogeneity. In order to approach these questions, C. capitata single-sex laboratory populations of 15 and 30 days old were subjected to a chill-coma recovery assay, and separated according to their recovery time in three subgroups: Fast-Subgroups, Intermediate-Subgroups, and Slow-Subgroups. Thereafter, we analyzed their survival, behavioral, and gene expression outputs. In female and old male populations, we found that flies with the slowest recovery time had a reduced life expectancy, a higher initial mortality rate, and a worse climbing performance compared with flies that recovered faster. Therefore, we were able to separate subgroups that developed chilling-injury from subgroups that had a reversible full recovery after cold exposure. The gene expression analysis of the heat shock protein genes hsp70 and hsp83 showed no clear association with the parameters studied. Interestingly, thorax expression levels of the Cu/Zn superoxide dismutase gene were elevated during the recovery phase in the Fast-Subgroups, but remained constant in the Slow-Subgroups that developed chilling-injury. On the other hand, none of the young male subgroups seemed to have suffered irreversible damage. Thus, we concluded that depending on age and population heterogeneity, chill-coma recovery time points out significant differences on individual cold tolerance. Moreover, the inability to properly induce the antioxidant defense system to counteract the oxidative damage caused by cold seems to contribute to the development of chilling-injury.

Genetic elimination of field-cage populations of Mediterranean fruit flies

The Mediterranean fruit fly (medfly, Ceratitis capitata Wiedemann) is a pest of over 300 fruits, vegetables and nuts. The sterile insect technique (SIT) is a control measure used to reduce the reproductive potential of populations through the mass release of sterilized male insects that mate with wild females. However, SIT flies can display poor field performance, due to the effects of mass-rearing and of the irradiation process used for sterilization. The development of female-lethal RIDL (release of insects carrying a dominant lethal) strains for medfly can overcome many of the problems of SIT associated with irradiation. Here, we present life-history characterizations for two medfly RIDL strains, OX3864A and OX3647Q. Our results show (i) full functionality of RIDL, (ii) equivalency of RIDL and wild-type strains for life-history characteristics, and (iii) a high level of sexual competitiveness against both wild-type and wild-derived males. We also present the first proof-of-principle experiment on the use of RIDL to eliminate medfly populations. Weekly releases of OX3864A males into stable populations of wild-type medfly caused a successive decline in numbers, leading to eradication. The results show that genetic control can provide an effective alternative to SIT for the control of pest insects.

Cold Tolerance of the Mediterranean Fruit Fly in Date and Mandarin

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is an endemic pest in Israel and there can be low levels of infestation of dates (Phoenix dactylifera L.). Because C. capitata is considered a quarantine pest by several major importing countries, the export of fresh dates requires the elimination of this pest. For mandarin, cold storage at 1.11°C for 15 d is considered to be an effective treatment for the elimination of C. capitata. In this study, we compared the cold tolerance of C. capitata in "Barhi" dates to that of C. capitata in mandarins (Citrus unshiu Marcovitch, "Satsuma"). In Barhi dates, we found the third instars to be the most cold-tolerant as compared with other life stages. Ceratitis capitata in date fruits were significantly less cold-tolerant than C. capitata in Satsuma mandarins. The last viable larvae in dates and mandarins were found after 8 and 13 d of treatment, respectively, and the calculated mortality curves in the two crops were significantly different. These results demonstrate that C. capitata is more sensitive to cold treatment when in date fruits than in mandarins. Therefore, the quarantine cold treatments used to eliminate C. capitata from mandarins should be sufficiently effective if applied to fresh date fruits.

The smart aerial release machine, a universal system for applying the sterile insect technique

Background

Beyond insecticides, alternative methods to control insect pests for agriculture and vectors of diseases are needed. Management strategies involving the mass-release of living control agents have been developed, including genetic control with sterile insects and biological control with parasitoids, for which aerial release of insects is often required. Aerial release in genetic control programmes often involves the use of chilled sterile insects, which can improve dispersal, survival and competitiveness of sterile males. Currently available means of aerially releasing chilled fruit flies are however insufficiently precise to ensure homogeneous distribution at low release rates and no device is available for tsetse.

Methodology/Principal Findings

Here we present the smart aerial release machine, a new design by the Mubarqui Company, based on the use of vibrating conveyors. The machine is controlled through Bluetooth by a tablet with Android Operating System including a completely automatic guidance and navigation system (MaxNav software). The tablet is also connected to an online relational database facilitating the preparation of flight schedules and automatic storage of flight reports. The new machine was compared with a conveyor release machine in Mexico using two fruit flies species (Anastrepha ludens and Ceratitis capitata) and we obtained better dispersal homogeneity (% of positive traps, p<0.001) for both species and better recapture rates for Anastrepha ludens (p<0.001), especially at low release densities (<1500 per ha). We also demonstrated that the machine can replace paper boxes for aerial release of tsetse in Senegal.

Conclusions/Significance

This technology limits damages to insects and allows a large range of release rates from 10 flies/km² for tsetse flies up to 600 000 flies/km² for fruit flies. The potential of this machine to release other species like mosquitoes is discussed. Plans and operating of the machine are provided to allow its use worldwide.

Identification of pheromone components and their binding affinity to the odorant binding protein CcapOBP83a-2 of the Mediterranean fruit fly, Ceratitis capitata

The Mediterranean fruit fly (or medfly), Ceratitis capitata (Wiedemann; Diptera: Tephritidae), is a serious pest of agriculture worldwide, displaying a very wide larval host range with more than 250 different species of fruit and vegetables. Olfaction plays a key role in the invasive potential of this species. Unfortunately, the pheromone communication system of the medfly is complex and still not well established. In this study, we report the isolation of chemicals emitted by sexually mature individuals during the "calling" period and the electrophysiological responses that these compounds elicit on the antennae of male and female flies. Fifteen compounds with electrophysiological activity were isolated and identified in male emissions by gas chromatography coupled to electroantennography (GC-EAG). Within the group of 15 identified compounds, 11 elicited a response in antennae of both sexes, whilst 4 elicited a response only in female antennae. The binding affinity of these compounds, plus 4 additional compounds known to be behaviourally active from other studies, was measured using C. capitata OBP, CcapOBP83a-2. This OBP has a high homology to Drosophila melanogaster OBPs OS-E and OS-F, which are associated with trichoid sensilla and co-expressed with the well-studied Drosophila pheromone binding protein LUSH. The results provide evidence of involvement of CcapOBP83a-2 in the medfly's odorant perception and its wider specificity for (E,E)-α-farnesene, one of the five major compounds in medfly male pheromone emission. This represents the first step in the clarification of the C. capitata and pheromone reception pathway, and a starting point for further studies aimed towards the creation of new powerful attractants or repellents applicable in the actual control strategies.

Evaluation of candidate systems for mass trapping against Ceratitis spp. on La Réunion island

BACKGROUND

Two Ceratitis spp. coexist on the island of La Réunion, Ceratitis rosa (Karsch) and C. capitata (Wiedemann). The effectiveness of candidate systems based on attractants and traps to control both species was evaluated through comparative studies of trap types, attractants, insecticides and commercial complete systems.

RESULTS

The Ceratitis spp. most captured in all trials was C. rosa. Captures of C. rosa and C. capitata were not significantly different when Maxitrap® or Tephri-trap® were used. Captures with the Easy-trap® were lower for both species. The BioLure® Med Fly lure showed higher catches of C. rosa than Ferag® CC D TM. The proportion of dead C. rosa did not differ significantly when deltamethrin or dichlorvos was used. There were no significant differences in the capture of C. rosa and C. capitata between commercial systems composed of the lure Ferag® CC D TM, the Maxitrap® and dichlorvos and the BioLure® Unipak, the Tephri-trap® and dichlorvos. The Cera Trap® system performed less effectively.

CONCLUSION

The most effective traps for the capture of C. rosa and C. capitata were Maxitrap® and Tephri-trap®; the most effective attractants were BioLure® Med Fly for C. rosa and BioLure® Med Fly, BioLure® Unipak and Ferag® CC D TM for C. capitata. However, for both species the most effective commercial combinations of trap and attractant were Maxitrap® with Ferag® CC D TM and Tephri-trap® with BioLure® Unipak, both using dichlorvos. The insecticide deltamethrin showed good efficacy when used inside traps.

Improving the sterile sperm identification method for its implementation in the Area-wide Sterile Insect Technique Program against Ceratitis capitata (Diptera: Tephritidae) in Spain

The success of sterile males in area-wide sterile insect technique (aw-SIT) programs against Ceratitis capitata (Wiedemann) is currently measured by using indirect methods as the wild:sterile male ratio captured in monitoring traps. In the past decade, molecular techniques have been used to improve these methods. The development of a polymerase chain reaction-restriction fragment-length polymorphism-based method to identify the transfer of sterile sperm to wild females, the target of SIT, was considered a significant step in this direction. This method relies on identification of sperm by detecting the presence of Y chromosomes in spermathecae DNA extract complemented by the identification of the genetic origin of this sperm: Vienna-8 males or wild haplotype. However, the application of this protocol to aw-SIT programs is limited by handling time and personnel cost. The objective of this work was to obtain a high-throughput protocol to facilitate the routine measurement in a pest population of sterile sperm presence in wild females. The polymerase chain reaction-restriction fragment-length polymorphism markers previously developed were validated in Mediterranean fruit fly samples collected from various locations worldwide. A laboratory protocol previously published was modified to allow for the analysis of more samples at the same time. Preservation methods and preservation times commonly used for Mediterranean fruit fly female samples were assessed for their influence on the correct molecular detection of sterile sperm. This high-throughput methodology, as well as the results of sample management presented here, provide a robust, efficient, fast, and economical sterile sperm identification method ready to be used in all Mediterranean fruit fly SIT programs.

Thermal biology, population fluctuations and implications of temperature extremes for the management of two globally significant insect pests

The link between environmental temperature, physiological processes and population fluctuations is a significant aspect of insect pest management. Here, we explore how thermal biology affects the population abundance of two globally significant pest fruit fly species, Ceratitis capitata (medfly) and C. rosa (Natal fruit fly), including irradiated individuals and those expressing a temperature sensitive lethal (tsl) mutation that are used in the sterile insect technique. Results show that upper and lower lethal temperatures are seldom encountered at the field sites, while critical minimum temperatures for activity and lower developmental thresholds are crossed more frequently. Estimates of abundance revealed that C. capitata are active year-round, but abundance declines markedly during winter. Temporal autocorrelation of average fortnightly trap captures and of development time, estimated from an integrated model to calculate available degree days, show similar seasonal lags suggesting that population increases in early spring occur after sufficient degree-days have accumulated. By contrast, population collapses coincide tightly with increasing frequency of low temperature events that fall below critical minimum temperatures for activity. Individuals of C. capitata expressing the tsl mutation show greater critical thermal maxima and greater longevity under field conditions than reference individuals. Taken together, this evidence suggests that low temperatures limit populations in the Western Cape, South Africa and likely do so elsewhere. Increasing temperature extremes and warming climates generally may extend the season over which these species are active, and could increase abundance. The sterile insect technique may prove profitable as climates change given that laboratory-reared tsl flies have an advantage under warmer conditions.

Cold storage enhances the efficacy and margin of security in postharvest irradiation treatments against fruit flies (Diptera: Tephritidae)

Cold storage is used to preserve fruit quality after harvest during transportation in marketing channels. Low temperature can be a stressor for insects that reduces survivorship, and cold storage may contribute to the efficacy of postharvest quarantine treatments such as irradiation against quarantine insect pests. The combined effect of irradiation and cold storage was examined in a radiation-tolerant fruit fly, Bactrocera cucurbitae Coquillet (melon fly), and a radiation-intolerant fruit fly, Ceratitis capitata (Wiedemann) (Mediterranean fruit fly) (Diptera: Tephritidae). Third instars on diet or in papaya were treated with a sublethal radiation dose of 30 Gy and stored at 4 or 11 degrees C for 3-13 d and held for adult emergence. For both fruit fly species, survival of third instars to the adult stage generally decreased with increasing cold storage duration at 4 or 11 degrees C in diet or papaya. Survivorship differences were highly significant for the effects of substrate (diet > papaya), temperature (11 > 4 degrees C),and irradiation (0 > 30 Gy). Few Mediterranean fruit flies survived in any cold storage treatment after receiving a radiation dose of 30 Gy. No melon fly larvae survived to the adult stage after irradiation and 11 d cold storage at 4 or 11 degrees C in papayas. Cold storage enhances the efficacy and widens the margin of security in postharvest irradiation treatments. Potentially irradiation and cold storage can be used in combination to reduce the irradiation exposure requirements of quarantine treatments.

The distribution, relative abundance, and seasonal phenology of Ceratitis capitata, Ceratitis rosa, and Ceratitis cosyra (Diptera: Tephritidae) in South Africa

Ceratitis capitata (Wiedemann), Ceratitis rosa Karsch, and Ceratitis cosyra (Walker) are fruit fly species (Diptera: Tephritidae) of economic importance in South Africa. These pests cause direct damage to a number of commercially produced fruit and are of phytosanitary concern. A study was conducted to determine the distribution, relative abundance, and seasonal occurrence of the three species in different climatic regions of South Africa. The relative abundance and seasonal phenology of C. capitata and C. rosa were also compared between production areas and home gardens in Stellenbosch, Western Cape. Yellow bucket traps baited with Biolure were used to trap the flies over a 2-yr period in the different sampling areas. Different fruit types were sampled in Stellenbosch to determine fruit fly infestation. C. capitata was found to have a widespread distribution in South Africa, whereas C. rosa were absent from or only present in low numbers in the drier regions. C. cosyra was restricted to the North East and East coast, following a similar pattern to the distribution of marula, Sclerocarrya birrea, an important wild host. Fruit in home gardens provided a breeding ground for C. capitata and C. rosa and a source for infestation of orchards when fruit started to mature, highlighting the need for an area-wide strategy for the control of fruit flies.

Influence of modified atmosphere packaging on radiation tolerance in the phytosanitary pest melon fly (Diptera: Tephritidae)

Modified atmosphere packaging (MAP) produces a low-oxygen (O2) environment that can increase produce shelf life by decreasing product respiration and growth of pathogens. However, low O2 is known to increase insect tolerance to irradiation, and the use of MAP with products treated by irradiation before export to control quarantine pests may inadvertently compromise treatment efficacy. Melon fly, Bactrocera cucurbitae Coquillet (Diptera: Tephritidae), is an important economic and quarantine pest of tropical fruits and vegetables, and one of the most radiation-tolerant tephritid fruit flies known. The effect of low O2 generated by MAP on the radiation tolerance of B. cucurbitae was examined. Third-instar larval B. cucurbitae were inoculated into ripe papayas and treated by 1) MAP + irradiation, 2) irradiation alone, 3) MAP alone, or (4) no MAP and no irradiation, and held for adult emergence. Three types of commercially available MAP products were tested that produced O2 concentrations between 1 and 15%, and a sublethal radiation dose (50 Gy) was used to allow comparisons between treatments. Ziploc storage bags (1-4% O2) increased survivorship to adult from 14 to 25%, whereas Xtend PP61 bags (3-8% O2) and Xtend PP53 bags (11-15% O2) did not enhance survivorship to the adult stage in B. cucurbitae irradiated at 50 Gy. Radiation doses approved by the United States Department of Agriculture and the International Plant Protection Commission for B. cucurbitae and Ceratitis capitata (Wiedemann) (Mediterranean fruit fly) are 150 and 100 Gy, respectively. In large-scale tests, 9,000 B. cucurbitae and 3,800 C. capitata larvae infesting papayas in Ziploc bags were irradiated at 150 and 100 Gy, respectively, with no survivors to the adult stage. MAP can increase insect survivorship during irradiation treatment at certain doses and O2 concentrations, but should not compromise the efficacy of the 150-Gy generic radiation treatment for tephritid fruit flies or the 100-Gy radiation treatment for C. capitata.