A genetic sexing system to improve the sterile insect technique against the Mediterranean fruit fly

The autosomal recessive allele v wing (v) in the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), produces flies that when reared at 30 degrees C have stubby wings. The mutant was used to construct a translocation-based genetic sexing system in an attempt to improve the efficiency and effectiveness of the sterile insect release method for field control.     

Chemosterilant bait stations coupled with sterile insect technique: an integrated strategy to control the Mediterranean fruit fly (Diptera: Tephritidae)

During 2008 and 2009, the efficacy of the combination of two Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), control techniques, sterile insect technique (SIT) and a chemosterilant bait station system (Adress), was tested in three crops: citrus (Citrus spp.), stone fruit (Prunus spp.), and persimmon (Diospyros spp.). Two thousand sterile males were released per ha each week in the whole trial area (50,000 ha, SIT area). For 3,600 ha, within the whole trial area, 24 Adress traps per ha were hung (SIT + Adress area). Ten SIT + Adress plots and 10 SIT plots in each of three different fruit crops were arranged to assess Mediterranean fruit fly population densities and fruit damage throughout the trial period. To evaluate the efficacy of each treatment, the male and female populations were each monitored from August 2008 to November 2009, and injured fruit was assessed before harvest. Results showed a significant reduction in the C. capitata population in plots treated with both techniques versus plots treated only with the SIT. Likewise, a corresponding reduction in the percentage of injured fruit was observed. These data indicate the compatibility of these techniques and suggest the possibility of using Adress coupled with SIT to reduce C. capitata populations in locations with high population densities, where SIT alone is not sufficiently effective to suppress fruit fly populations to below damaging levels.     

Mortality of olive fruit fly pupae in California

Efforts to control the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae), in California have focused on insecticidal baits and biological control by parasitoids, which primarily target the adult and larval stages, respectively. The pupal stage, which occurs in the soil, has largely been overlooked. This study investigated mortality factors for olive fruit fly pupae in California olive orchards, using a combination of exclusion experiments and observation and trapping of potential predators. Results show predation and climatic factors contribute to pupal mortality. Ants (Formicidae) were the most numerous predators observed. Soil-borne pathogens caused no mortality in this study. Potential applications of these results in the development of a sustainable management program are discussed.     

Chilled packing systems for fruit flies (Diptera: Tephritidae) in the sterile insect technique

We evaluated three packing systems (PARC boxes, "GT" screen towers and "MX" screen towers) for the emergence and sexual maturation of sterile fruit flies, at three adult fly densities (1, 1.2 and 1.3 fly/cm2) and three food types. At the lowest density, results showed no significant differences in the longevity and flight ability of adult Anastrepha ludens (Loew) and Anastrepha obliqua Macquart among the three packing systems. Higher densities resulted in a decrease in these parameters. In the evaluation of the three food types, no significant differences were found either on longevity or flight ability of A. ludens. However, the greatest longevity for both sexes A. obliqua was obtained with commercial powdered Mb? and the mix of sugar, protein and corn starch on paper (SPCP) food types. The highest value for flight ability in A. obliqua males was obtained with powdered Mb? and SPCP food types, and for females with Mb? powdered food. Our data indicated that GT and MX screen tower packing systems are an alternative to the PARC boxes, since they were suitable for adult fly sexual maturation without any harm to their longevity or flight ability. The tested foods were equivalent in both fruit fly species, with the exception of the agar type for A. obliqua, which yielded the lowest biological parameters evaluated. Our results contribute to the application of new methods for the packing and release of sterile flies in large-scale programs.     

Medfly promoters relevant to the sterile insect technique

This review summarizes structural and functional studies on medfly promoters and regulatory elements that can be used for driving sex-specific, conditional and constitutive gene expression in this species. Sex-specific and conditional promoters are important for generating transgenic sexing strains that could increase the performance of the Sterile Insect Technique while strong constitutive promoters are necessary for developing sensitive transgenic marker systems. The review focuses on the functional analysis of the promoters of two male-specific and heat shock medfly genes. A special emphasis is put on the potential utility of these promoters for developing transgenic sexing strains.     

Developing transgenic Anopheles mosquitoes for the sterile insect technique

In the last 10 years the availability of the genome sequence of Anopheles gambiae and the development of a transgenic technology for several species of Anopheles mosquitoes have, in combination, helped in enabling us to gain several insights into the biology of these mosquitoes that is relevant to their capacity as vectors of the malaria parasite. While this information is anticipated to inform many novel vector control strategies, the technique most likely to benefit in the near future from the availability of a reliable transgenic technology is the sterile insect technique (SIT), which relies on releasing large numbers of sterile insects to compete for mates in the wild, leading to population suppression. Although SIT has been proven to work reliably for many insects, the construction of suitable strains, and induction of sterility, has until now been a laborious process, combining classical genetics with radiation-induced sterility. Using transgenesis to create strains of Anopheles suitable for SIT could potentially offer several advantages over current approaches, in that the basic design of transgenic constructs designed for other insects should be rapidly transferable to mosquitoes, and induction of sterility as a product of the transgenic modification could obviate the requirement for radiation and its associated deleterious effects. In this paper the progress of different transgenic approaches in constructing tools for SIT will be reviewed.     

Generic insect repellent detector from the fruit fly Drosophila melanogaster

Background

Insect repellents are prophylactic tools against a number of vector-bornediseases. There is growing demand for repellents outperforming DEET in costand safety, but with the current technologies R&D of a new product takesalmost 10 years, with a prohibitive cost of $30 million dollar inpart due to the demand for large-scale synthesis of thousands of testcompounds of which only 1 may reach the market. R&D could be expeditedand cost dramatically reduced with a molecular/physiological target tostreamline putative repellents for final efficacy and toxicologicaltests.

Methodology

Using olfactory-based choice assay we show here that the fruit fly isrepelled by not only DEET, but also IR3535 and picaridin thus suggestingthey might have “generic repellent detector(s),” which may be ofpractical applications in new repellent screenings. We performed single unitrecordings from all olfactory sensilla in the antennae and maxillary palps.Although the ab3A neuron in the wild type flies responded to picaridin, itwas unresponsive to DEET and IR3535. By contrast, a neuron housed in thepalp basiconic sensilla pb1 responded to DEET, IR3535, and picaridin, withapparent sensitivity higher than that of the DEET detectors in themosquitoes Culex quinquefasciatus and Aedesaegypti. DmOr42a was transplanted from pb1 to the “emptyneuron” and showed to be sensitive to the three insect repellents.

Conclusions

For the first time we have demonstrated that the fruit fly avoids not onlyDEET but also IR3535 and picaridin, and identified an olfactory receptorneuron (ORN), which is sensitive to these three major insect repellents. Wehave also identified the insect repellent-sensitive receptor, DmOr42a. Thisgeneric detector fulfils the requirements for a simplified bioassay forearly screening of test insect repellents.     

Age-dependent variation in mating success of sterile male Mediterranean fruit flies (Diptera: Tephritidae): implications for sterile insect technique

The sterile insect technique (SIT) is widely used in integrated programs against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Unfortunately, the mass-rearing procedures inherent to the SIT often lead to a reduction in the mating ability of the released males. To counter this deficiency, SIT programs rely upon the production and release of large numbers of sterile males to achieve high overflooding (sterile:wild male) ratios. To ensure a high release volume, emergence facilities release adult males at a young age (2 d old in some cases). The primary objective of this study was to describe age-dependent variation in the mating propensity and competitiveness of sterile males of C. capitata. Males that were 2 or 3 d old had lower mating propensity than males that were > or =4 d old, and 3-d-old males had lower mating competitiveness than males that were > or =4 d old. Given these results, we measured the effect of a longer holding period on male mortality in storage boxes. With delayed food placement, males held in storage boxes for 4 d after emergence showed no higher mortality than males held for only 2 d (the standard interval). Using large field enclosures, we compared the levels of egg sterility attained via releases of 2- versus 4-d-old sterile males at two overflooding ratios (5:1 and 100:1). At the lower ratio, the proportion of unhatched eggs observed for trials involving 2-d-old sterile males was not, on average, significantly higher than that observed for matings between wild flies (33 versus 25%, respectively), whereas the level of egg sterility observed for releases of 4 d old sterile males was 62%. At the 100:1 overflooding ratio, the proportion of unhatched eggs associated with the 2-d-old sterile males was 58%, a level not significantly different from that induced by 4-d-old sterile males at the 5:1 ratio and significantly lower than the level (79%) observed for 4-d-old sterile males at 100:1 overflooding ratio. The implications of these results for SIT are discussed.     

Control of the mediterranean fruit fly (Ceratitis capitata) using sterile males: Effects of nitrogen and chilling during gamma-irradiation of puparia

Nitrogen has proved effective in protecting puparia of Ceratitis capitata (Wiedemann) from gamma-irradiation induced damage as evidenced by increased adult emergence from early irradiated puparia, adult male survival, and male fertility. Chilling to 4° during irradiation had the opposite effect and it is concluded that the extent of damage which can be altered by these treatments is due to oxygen-dependent effects of irradiation. Increased fertility after irradiation in nitrogen may be due to increased sexual vigour rather than to reduction in damage of genetic material but this has not been proved. Effects on percentage adult emergence, survival and fertility are probably manifestations of the same phenomenon of irradiation-induced lethargy. It is considered that the effect of treatment with nitrogen at 25° or chilling to 4° in air during irradiation may be of value in increasing the flexibility of a large-scale campaign to control C. capitata by the sterile-insect release method.Adults from puparia of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), subjected to sterilizing doses of gamma radiation, survive best when treated late in puparial life (Arroyo et al. 1965). This fact greatly affects the logistics of any large-scale sterilization programme (Knipling 1960) for the control of this or other insects in the field (see Smith 1963). Hence we have tried to separate the genetic and somatic effects of gamma-irradiation upon puparia of C. capitata. We hoped that if somatic effects could be lessened without affecting the degree of sterility induced by a given dose, the age-range of puparia which could be successfully sterilized might be increased, thus allowing greater flexibility in the development of a control programme.The lessening of radiation-induced damage under conditions of low oxygen tension has been well established in both plant and animal tissues (Patt & Brues 1954; O'Brien & Wolfe 1964). Nitrogen increases the radiation resistance of the wasp Habrobracon during development (Clark & Herr 1955), and Baldwin and Salthouse (1959) showed that oxygen deficiency protected the bug Rhodnius from the dual effect of delayed moulting and burning of the epidermis following administration of X-rays.Present results involving irradiation of C. capitata puparia in nitrogen at 25° or in air at 4° show that some protection from lethal somatic effects is possible.

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Zusammenfassung Es konnte gezeigt werden, dass bei der Bestrahlung der Puparien von Ceratitis capitata (Wiedemann) mit 10 k-rad Gammastrahlen in einer Stickstoffatmosphäre der erreichte Prozentsatz schlüpfender Imagines—im Vergleich mit der Bestrahlung in Luft bei 25° oder 4°C—vergrössert ist, wenn die Puparien am 4. Tag der Entwicklung bei 25°C behandelt werden. Die Schutzwirkung des Stickstoffs ist noch grösser bei einer Dosis von 30 k-rad. Nach Bestrahlung mit 10 k-rad in einem späteren Stadium der Puparien-Entwicklung blieb das Überleben der geschlüpften Männchen von der Behandlung mit Stickstoff oder von der Abkühlung unbeeinflusst. Jedoch ergaben am 4. Tag der Entwicklung behandelte Puparien nach Bestrahlung in Stickstoff länger lebende Männchen und das Überleben war nach Bestrahlung in Luft bei 4°C am geringsten. Diese Ergebnisse weisen auf die Existenz einer, sekundären Letalwirkung der Bestrahlung hin, die von Sauerstoff abhängig ist, da Stickstoff die Sauerstoff-spannung in den Geweben herabsetzt, während Abkühlung auf 4°C die Löslichkeit von Sauerstoff in den Gewebeflüssigkeiten erhöht. Der primäre Letaleffekt der Bestrahlung ist der, welcher die Weiterentwicklung durch Schädigung der sich differenzierenden Gewebe verhindert. Der Sekundäreffekt verhindert das Schlüpfen der voll entwickelten pharaten Imago aus ihrem Puparium, und es wird angenommen, dass die auf Bestrahlung während früher Entwicklungsstadien folgende Einschränkung der Überlebensfähigkeit der Erwachsenen — wie sie von anderen Untersuchern bei anderen Insekten gefunden wurde — eine Manifestation der gleichen Erscheinung darstellt. Es wird vermutet, dass diese sauerstoffabhängige sekundäre Letalität irgendwie mit einem Eingreifen in den normalen Atmungsstoffwechsel des Insekts zusammenhängt.Es wird im Vergleich mit der Bestrahlung in Luft bei 25°C eine Steigerung der Fertilität der in Stickstoff bei 25°C bestrahlten Männchen und eine Minderung der Fertilität nach Bestrahlung in Luft bei 4°C festgestellt. Das könnte eher eine Folge von Veränderungen in der sexuellen Vitalität als von Veränderungen in der Häufigkeit der Induktion dominanter Letalfaktoren in den Spermatozoen sein. Weitere Untersuchungen zur Bestimmung dieses Punktes sind notwendig.Es wird angenommen, dass die Wirkungen einer Behandlung mit Stickstoff oder Abkühlung auf 4°C während der Bestrahlung von Nutzen für die Steigerung der Flexibilität bei einer weitgespannten Bekämpfungsaktion von C. capitata durch die S.I.R.M. sein dürften.

     

Low temperature storage effects on two olive fruit fly parasitoids

Effects of cold storage temperatures and storage duration were evaluated for Psyttalia humilis (Silvestri) from Namibia and Psyttalia ponerophaga (Silvestri) from Pakistan, braconid parasitoids of Bactrocera oleae (Rossi) imported to California, USA. Immature stages of P. humilis were exposed to 4, 6, 8, 10, or 12 °C for 1, 2 or 4 months (pupa only at 4 and 12 °C) and then held at 24 °C for adult emergence. Less than 5 % of parasitoids in the 4–8 °C treatments survived, regardless of storage duration. At the 10 °C treatment, adult survival decreased with increased storage duration, but increased with advancing developmental stages. Survival was not affected at the 12 °C treatment. Adult P. humilis were exposed to 6, 8, 10 °C for short periods (1, 2, 4, or 6 weeks) or ambient winter conditions in Parlier, California, USA (about 9 °C). Regardless of storage temperature, P. humilis reproduction was reduced after storage of four and six weeks. Similarly, after 4 months at ambient winter temperatures, P. humilis reproduction was reduced. Psyttalia ponerophaga pupae stored at 6 °C for 41–97 days had decreased survival and increased developmental time. Survival of P. ponerophaga pupae ranged from 13.9–52.1 %, whereas under similar storage conditions survival of P. humilis was <0.7 %, suggesting P. ponerophaga is more cold tolerant than P. humilis.     

Effect of the presence of olive fruit on ovarian maturation in the olive fruit fly, Dacus oleae, under laboratory conditions

Ovarian maturation was prevented in 7-, 22-, 23- and 28-day-old females of Dacus oleae (Gmelin) (Diptera: Tephritidae), developed in the pre-imaginal stages at LD 12:12, 19±1°C and kept as adults at LD 16:8, 26±1°C without access to olive fruits. In females of the above ages having continuous access to olive fruits and held under the same photoperiod and temperature conditions, 54, 87 and 100%, respectively, had mature oocytes. When the females had access to domes of paraffin wax, the percentages of females with mature oocytes were intermediate between those with and those without access to olive fruits. Under the above photoperiod and temperature conditions unfavorable for maturation, 50% of 4-week-old females had mature oocytes if exposed for one week to olive fruits during their first week and 91% if exposed during their 4th week of adult life. The respective percentages with wax domes in the cages were again intermediate between those with olives and those without olives or wax domes. The presence of olive fruits had also a strong positive effect on the ovarian maturation of females which developed from egg through the adult stage at LD 16:8, 26±1°C, a condition favoring ovarian maturation. Access to wax domes had again an intermediate effect on maturation. It is concluded therefore that the lack of ovarian maturation of D. oleae females which is observed under a short photophase during the pre-imaginal stages if followed by a long photophase and an increase of temperature during the adult stage, continues at least till the end of the 4th week of adult life in the absence of olive fruits but is averted when such fruits are offered to the adult flies.

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Résumé La maturation ovarienne des femelles adultes agées de 7, 22–23 et 28 jours de D. oleae ayant accompli leur développement embryonnaire, larvaire et nymphal en LD 12:12, 19±1°C et maintenues en LD 16:8, 26±1°C, sans accès à des olives, est inhibée. Dans les mêmes conditions, mais avec accès permanent à des olives, 54% des femelles ont des ovocytes mûrs à 7 jours, 87% à 22–23 jours et 100% à 28 jours. Avec des femelles ayant accès à des domes de paraffine, les pourcentages d'individus ayant des ovocytes mûrs sont intermédiaires entre ceux des deux situations précédentes. Dans les conditions cidessus défavorables à la maturation ovarienne, 50% des femelles de 28 jours ont des ovocytes mûrs si elles sont en présence d'olives durant leur première semaine de vie imaginale et 91% si elles sont en présence la 4éme semaine. Les pourcentages respectifs concernant les femelles pourvues de dômes de paraffine sont encore intermédiaires entre ceux des femelles avec olives et ceux de femelles privées de tout substrat. La présence d'olives a aussi un effet fortement positif sur la maturation ovarienne de femelles ayant accompli leur développement pre-imaginal et maintenues aussi à l'etat adulte en conditions LD 16:8, 26±1°C, favorisant la maturation ovarienne. L'accès à des dômes de paraffine a, là encore, un effet intermédiaire. On conclut par conséquent que la non maturation ovarienne des femelles de D. oleae qui est causée par une photopériode à jour court pendant la vie pre-imaginale accompagné par une photopériode à jour long et une augmentation de la température pendant la vie imaginale persiste au moins jusqu'à la fin de la quatrième semaine de la vie imaginale en absence d'olives, mais ne se produit pas si on met les femelles adultes en présence d'olives.

     

Improving the biological control of leafminers (Diptera: Agromyzidae) using the sterile insect technique

The leafminer Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) is a worldwide pest of ornamental and vegetable crops. The most promising nonchemical approach for controlling Liriomyza leafminers in greenhouses is regular releases of the parasitoid Diglyphus isaea (Walker) (Hymenoptera: Eulophidae). In the current study, we examine the hypothesis that the use of D. isaea for biological control of leafminers in greenhouse crops may be more practical and efficient when supplemented with additional control strategies, such as the sterile insect technique (SIT). In small cages, our SIT experiments suggest that release of sterile L. trifolii males in three sterile-to-fertile male ratios (3:1, 5:1, and 10:1) can significantly reduce the numbers of the pest offspring. In large cage experiments, when both parasitoids and sterile males were released weekly, the combined methods significantly reduced mine production and the adult leafminer population size. Moreover, a synergistic interaction effect between these two methods was found, and a model based on our observed data predicts that because of this effect, only the use of both methods can eradicate the pest population. Our study indicates that an integrated pest management approach that combines the augmentative release of the parasitoid D. isaea together with sterile leafminer males is more efficient than the use of either method alone. In addition, our results validate previous theoretical models and demonstrate synergistic control with releases of parasitoids and sterile insects.     

Molecular technologies to improve the effectiveness of the sterile insect technique

The application of the Sterile Insect Technique (SIT) in area-wide integrated pest management (AW-IPM) programmes continues to increase. However, programme efficiency can still be considerably enhanced when certain components of the technology are improved, such as the development of improved strains for mass rearing and release. These include strains that (1) produce only male insects for sterilization and release and (2) carry easily identifiable markers to identify released sterile insects in the field. Using both classical and modern biotechnology techniques, key insect pests are targeted, where SIT programmes are being implemented. The pests include mosquitoes, the Mexican fruit fly, the codling moth, the oriental fruit fly and the pink bollworm. This special issue summarizes the results of research efforts aimed at the development and evaluation of new strains to a level where a decision can be made as to their suitability for use in large scale SIT programmes. Major beneficiaries will be operational AW-IPM programmes that apply the SIT against major insect pests.     

苹果蠹蛾不育昆虫释放技术研究进展

不育昆虫释放技术(sterile insect technique,SIT)是一种环境友好、可作为大面积害虫综合治理(AW-IPM)的防治技术,是以压倒性比例释放不育昆虫来减少田间同种害虫繁殖量的害虫治理方法。苹果蠹蛾Cydia pomonella(L.)是世界重要的梨果类害虫,现已入侵世界5洲71国。本文综述了苹果蠹蛾大规模饲养技术、辐射不育技术、释放技术3个关键环节的研究与技术进展,主要包括:苹果蠹蛾人工饲料、实验种群建立、饲养设备与条件、收集和质量评估、长距离运输、辐射源与设备、辐射剂量与敏感性、释放方法、释放标记和释放量等,并介绍了各国采用SIT技术的应用效果。苹果蠹蛾在我国新疆、甘肃、宁夏、内蒙、黑龙江、吉林6个省区发现,对我国苹果产业安全生产构成严重威胁,我国很有必要引进并建立苹果蠹蛾SIT防治技术体系。     

The biology of Bracon celer as a parasitoid of the olive fruit fly

A series of laboratory experiments was conducted on a colony of Bracon celer Szépligeti (Hymenoptera: Braconidae) reared on the olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae). Female B. celer preferentially probe and oviposit into olives containing late third-instar fly larvae. The parasitoid develops as a solitary, ectoparasitic idiobiont. Mean development time (oviposition to adult eclosion) at 22 °C was, for females, 36±1 (SE) days, and for males, 34±1 days. The mean longevity of adult female wasps when provided honey and water was significantly greater than when they were provided water alone, or nothing. The females produced an average of 9.7±7.2 progeny during their lifetimes, but production levels in the insectary colony suggested that this level of fecundity was artificially low and could be improved. The discrepancy may be a consequence of constraints on oviposition behavior imposed by the experimental design. The results are discussed with respect to insectary production methods and the potential use of B. celer as a biological control agent for olive fly in California.     

Comparative evaluation of two olive fruit fly parasitoids under varying abiotic conditions

Psyttalia lounsburyi (Silvestri) and P. humilis (Silvestri) (Hymenoptera: Braconidae) were evaluated in California for their potential to control the invasive olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae). Psyttalia lounsburyi is a specialist on B. oleae while P. humilis also attacks other tephritid species. Field cage trials, conducted from 2006 to 2009, were used to compare P. lounsburyi and two populations of P. humilis (Kenya and Namibia) in California’s interior valley and coastal regions. Both parasitoid species reproduced on B. oleae in all trials. Under similar abiotic conditions, offspring production per female was higher in P. humilis than in P. lounsburyi, suggesting that host specificity by P. lounsburyi does not confer a higher efficiency on B. oleae in cultivated olives. Two abiotic factors were shown to impact parasitoid efficiency. First, adult parasitoid survival was poor during periods of high summer temperatures, common to the olive production areas in California’s interior valleys. Second, parasitism levels were lower on B. oleae larvae feeding in larger Ascolano cv. fruit than in smaller Manzanillo cv. fruit. Results are discussed relative to biological control of B. oleae in commercial olives and the usefulness of natural enemies specialized to attack fruit flies in wild olives compared with the larger cultivated olive fruit.