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

Mating activity of olive fruit fly Bactrocera oleae (Rossi) (Diptera Tephritidae): Time duration related with phtoperiod and temperature: Wild and laboratory insects

The olive fruit fly is the single insect key pest for olive culture, in the majority of the areas where this is practiced, causing major economic loss during favourable for the insect periods of the year. So far, main control measures against this insect include chemical insecticides, with all the adverse side effects on the produce and the environment. Experiments related with the sterile insect technique, showed that a considerable degree of mating isolation occurs between wild and laboratory mass-reared insects, due to differential mating time within the day. This could result in failure of this particular methodology. In nature, Bactrocera species mate at the end of the natural photophase, during dusk. The present thesis aimed at investigating the environmental factors which affect the time of mating activity of the olive fruit fly. Laboratory and wild populations of the insect were studied under various photoperiodic and temperature regimes. Experiments were also conducted in order to clarify the influence of environmental conditions on timing and duration of copulation, and to explore the speed of adaptation in new photoperiods. The inheritance of circadian copulation pattern was also studied. The present results indicated that: 1) Both wild and laboratory strains of the olive fruit fly mate towards the end of photophase, with the activity of wild flies occurring mostly within 1 ½ - 2 hours before the onset of darkness, while the mating activity of lab insects expanded over 4 ½ hours before the onset of scotophase, respectively. 2) Under long daylight photophase regime, the initiation of copulations tends to occur earlier within the photophase. 3) The duration of copulation (time in copula) increases with that of photophase. 4) Temperature was found to affect strongly the timing and duration of copulations. The combination of temperature with photophase duration affected even stronger the timing of copulation. 5) The above findings apply to both laboratory and wild olive fly strains. 6) Insects adapted their mating timing to a new photoperiodic regime within 24 hours. This makes difficult an absolute synchronization of released and wild population mating activities in SIT methodologies. 7) Ten generations of selection of laboratory strain to early or late within photophase copulation, resulted in no difference when compared with the standard strain mating timing.Ο δάκος της ελιάς αποτελεί τον κυριότερο εχθρό για την ελαιοκαλλιέργεια στις περισσότερες περιοχές όπου αυτή εξασκείται, προκαλώντας μεγάλες οικονομικές ζημίες σε ευνοικές για τον πληθυσμό του περιόδους του έτους. Ο κυριότερος τρόπος καταπολέμησης του, παρά την εκτεταμένη έρευνα σε πολλά πεδία της συμπεριφοράς και της γενικότερης βιολογίας του, είναι η χρήση χημικών σκευασμάτων μέχρι και τις μέρες μας, με το πλήθος των αρνητικών παρενεργειών που αυτή συνεπάγεται για το περιβάλλον. Πειράματα σχετιζόμενα με την μέθοδο καταπολέμησης με εξαπόλυση στείρων εντόμων, έδειξαν ότι, μεταξύ άλλων, υπάρχει αξιόλογη συζευκτική απομόνωση μεταξύ των δυο πληθυσμών (άγρια και εργαστηριακά), εξαιτίας της διαφορετικής ώρας σύζευξης σε αυτούς, με αποτέλεσμα να δυσχεραίνεται η επιτυχής καταπολέμηση του εντόμου με την συγκεκριμένη μέθοδο. Η φυσική ώρα έναρξης της σύζευξης στα είδη Bactrocera και ιδιαίτερα στο δάκο είναι στο τέλος της φυσικής φωτόφασης, στο λυκόφως. Η παρούσα διδακτορική διατριβή είχε σαν στόχο να διερευνήσει σε βάθος τους περιβαλλοντικούς παράγοντες που επηρεάζουν τον χρόνο συζευκτικής δραστηριότητας του εντόμου. Για τον σκοπό αυτό, μελετήθηκαν εργαστηριακοί και άγριοι πληθυσμοί του εντόμου υπό διάφορες συνθήκες φωτοπεριόδου, θερμοκρασίας και συνδυασμού αυτών. Τα πειράματα είχαν ως σκοπό να αποσαφηνίσουν την επίδραση των περιβαλλοντικών συνθηκών στην ώρα και διάρκεια σύζευξης, και να καταδείξουν την σημασία της ταχείας προσαρμογής σε νέες συνθήκες, και της κληρονόμησης του κιρκάδιου μηχανισμού ρύθμισης της σύζευξης. Τα αποτελέσματα έδειξαν ότι : Α) Τόσο τα άγρια όσο και τα εργαστηριακά έντομα συζεύγνηνται στο τέλος της φωτόφασης, πλην όμως η συζευκτική δραστηριότητα των αγρίων καταλαμβάνει τις τελευταίες 1 ½ - 2 ώρες φωτόφασης, ενώ των εργαστηριακών απλώνεται στις τελευταίες 4 ½ ώρες φωτόφασης. Β) Όσο μεγαλώνει η φωτόφαση τόσο τα έντομα τείνουν να επεκτείνουν ενωρίτερα μέσα σε αυτήν τις συζεύξεις τους. Γ) Η διάρκεια σύζευξης μεταβάλλεται ανάλογα με το μήκος της φωτόφασης. Δ) Η θερμοκρασία φαίνεται να έχει ισχυρή επίδραση στην κατανομή και στην διάρκεια των συζεύξεων, και ο συνδυασμός θερμοκρασίας-φωτοπεριόδου λειτουργεί συνεργιστικά στα ανωτέρω. Ε) Τα ανωτέρω παρατηρήθηκαν τόσο σε άγρια όσο και σε εργαστηριακά έντομα. Ζ) Τα έντομα έχουν την ικανότητα να προσαρμόζουν τον χρόνο σύζευξης σε νέα φωτοπερίοδο μέσα σε ένα εικοσιτετράωρο, γεγονός που αποκλείει την χρήση της φωτοπεριόδου για εξασφάλιση ταυτότητας χρόνου σύζευξης μεταξύ στείρων εντόμων και άγριου πληθυσμού στο φυσικό περιβάλλον. Η) Η δημιουργία στελεχών μέσω επιλογής όσον αφορά στην ώρα σύζευξης (πείραμα 10 διαδοχικών γενεών), δεν φαίνεται να δείχνει σημαντικές διαφορές σε σχέση με τον πληθυσμό ελέγχου

An Overview of Phytosanitary Irradiation Requirements for Australian Pests of Quarantine Concern

Phytosanitary irradiation is used to prevent the introduction or spread of unwanted plant pests and diseases found in horticulture commodities, both in a domestic and international trade setting. Australia started exporting irradiated horticulture commodities to New Zealand in 2004. Since then, exports of irradiated products have continued to grow as phytosanitary irradiation has become more widely accepted for the treatment of plant pests by our international trading partners. Domestically, Food Standards Australia New Zealand (FSANZ) now allows irradiation of all fresh fruits and vegetables using an irradiation dose of 150 to 1000 Gy for all insect pests. To facilitate further domestic and international trade in Australian irradiated horticulture products, we conducted a literature review to perform the following: (1) identify information gaps (minimum absorbed irradiation dose) for Australian pests of quarantine concern, and (2) identify where differences may exist between the minimum absorbed dose and the regulated dose set, and that is accepted by Australia and key international trading partners. In Australia, a minimum absorbed dose of 400 Gy can be used to treat all insect pests of quarantine concern. However, a lower minimum absorbed dose of 150 Gy is used for many fruit fly species that are important for domestic and international trade. For a limited number of priority insect and non-insect pests highlighted by the horticulture sector, there were gaps found for minimum absorbed irradiation dose in the literature. These pests include Vineyard snail, Serpentine leaf miner and Fuller’s rose weevil. Studies to establish the minimum absorbed dose for Vineyard snails, Serpentine leaf miners and Fuller’s rose weevil are recommended. In addition to the gaps identified for irradiation dose, there is merit in conducting further research to refine (lower) the minimum absorbed dose for specific pests and priority commodities where irradiation has an impact on quality. A reduction in dose may not only benefit product quality but will also reduce both treatment time and cost

Improving olive fruit fly Bactrocera oleae (Diptera : Tephritidae) adult and larval artificial diets, microflora associated with the fly and evaluation of a transgenic olive fruit fly strain

Research on the olive fruit fly Bactrocera oleae (Rossi) – rearing simplification, insect microflora and transgenic strain evaluation – yielded several findings: (1) incorporation of antibiotics in the adult diet is evidently not needed; (2) colonization appears to be easier when wild adults are collected from the field instead of using mature larvae emerging from field-collected infested olives; (3) a combination of standard solid starter with liquid (no cellulose powder) finisher impregnated in synthetic sponge larval diets was more promising compared with all-liquid diets; (4) molecular analysis revealed extensive differences in bacterial species associated with the fly between laboratory flies and strains from different olive varieties, as well as between strains originating from different seasons of the year; (5) when an enhanced green fluorescent protein transgenic strain was compared with the standard long mass-reared strain, it proved significantly inferior according to all quality control tests applied, i.e. egg production, egg hatch, larval-stage duration, pupal recovery, pupal weight, adult emergence and adult survival. The aforementioned findings are discussed in the context of mass rearing and quality requirements for more successful implementation of the sterile insect technique against this pest.9 page(s

Effects of radiation on the fertility of the Ethiopian fruit fly, Dacus ciliatus

The Ethiopian fruit fly, Dacus ciliatus (Loew) (Diptera: Tephritidae), is a significant pest of cucurbit crops in Asia and Africa and is currently controlled with insecticides. The sterilizing effect of gamma radiation on D. ciliatus adults was investigated to assess the suitability of sterile insect technique (SIT) for use as an alternative, non-chemical strategy for the control of this pest. Late pupae (48 h before emergence) were irradiated with 60, 80, 100, 120, and 140 Gy of gamma rays emitted by a 60Co source. Following emergence, the biological characteristics of the experimental cohorts (including all possible male-female combinations of irradiated and untreated flies) were recorded. No significant negative effects of irradiation on pupal eclosion or the ability of newly emerged flies to fly were observed. Samples of eggs at reproductive fly-ages (12-, 15-, and 17-day-old pairs) were collected and their hatch rates were assessed. At 60 Gy, females were completely sterilized, whereas complete sterilization of the males was observed only at 140 Gy (a small amount of fertility persisted even at 120 Gy). In addition to the above experiments, three fruit infestation trials were conducted with zucchini [Cucurbita pepo L. (Cucurbitaceae)] as the plant host and the pupae produced in those trials were collected and recorded. We observed significant (ca. 10%) infestation following treatment with up to 120 Gy and zero progeny only at 140 Gy, mirroring the egg-hatch results. Our findings support the feasibility of SIT for the control of D. ciliatus.6 page(s

Modeling insect population fluctuations with satellite land surface temperature

The simulation of insect pest populations in agricultural and forest ecosystems is an important and useful tool for integrated pest management (IPM). Insect population models are mainly driven by environmental temperature data, which are usually collected from agrometeorological stations or derived from geographic statistical extrapolations. The present study describes the modeling of olive fly (Bactrocera oleae) populations in the Eastern Mediterranean region using the MODIS (Moderate Resolution Image Spectro Radiometer) land surface temperature (LST) product from NASA TERRA satellite. These data, together with in situ temperature data, were used to estimate the tree-canopy temperatures at the pixel resolution (1 km). The estimated canopy temperature was used as input for the olive fly population model. Our main aim was to demonstrate the use of satellite-acquired information for modelling biological and ecological phenomena. Eleven years (2001–2012) of olive fly population fluctuations were simulated for three different geographic locations, representing different geo-climatic conditions. The model successfully simulated the seasonal population fluctuations throughout the 11-year period and did a good job of connecting all of the life stages of the insect. To evaluate the validity of these findings, we compared them with adult olive-fly trapping data. We observed a high degree of correlation between the trapping data and our model's predictions. Here, we demonstrate that satellite thermal data can be used to predict insect pest population fluctuations for IPM purposes. The study also advances some new modelling concepts, such as the “window of opportunity” which links physiological development with chronological age.9 page(s

Sex allocation in a polyembryonic parasitoid with female soldiers: an evolutionary simulation and an experimental test.

Parasitoid wasps are convenient subjects for testing sex allocation theory. However, their intricate life histories are often insufficiently captured in simple analytical models. In the polyembryonic wasp Copidosoma koehleri, a clone of genetically identical offspring develops from each egg. Male clones contain fewer individuals than female clones. Some female larvae develop into soldiers that kill within-host competitors, while males do not form soldiers. These features complicate the prediction of Copidosoma's sex allocation. We developed an individual-based simulation model, where numerous random starting strategies compete and recombine until a single stable sex allocation evolves. Life-history parameter values (e.g., fecundity, clone-sizes, larval survival) are estimated from experimental data. The model predicts a male-biased sex allocation, which becomes more extreme as the probability of superparasitism (hosts parasitized more than once) increases. To test this prediction, we reared adult parasitoids at either low or high density, mated them, and presented them with unlimited hosts. As predicted, wasps produced more sons than daughters in all treatments. Males reared at high density (a potential cue for superparasitism) produced a higher male bias in their offspring than low-density males. Unexpectedly, female density did not affect offspring sex ratios. We discuss possible mechanisms for paternal control over offspring sex

Suppression of cuelure attraction in male Queensland fruit flies provided raspberry ketone supplements as immature adults.

Tephritid fruit flies are amongst the most damaging insect pests of horticulture globally. Some of the key fruit fly species are managed using the sterile insect technique (SIT), whereby millions of sterile males are released to suppress reproduction of pest populations. Male annihilation technique (MAT), whereby sex specific lures are used to attract and kill males, is often used to reduce wild male numbers before SIT programs commence, providing released sterile males an increased numerical advantage. Overall program efficacy might be improved if MAT could be deployed simultaneously with SIT, continuously depleting fertile males from pest populations and replacing them with sterile males. However, such 'male replacement' requires a means of suppressing attraction of released sterile males to lures used in MAT. Previous studies have found that exposure of some fruit flies to lure compounds as mature adults can suppress subsequent response to those lures, raising the possibility of pre-release treatments. However, this approach requires holding flies until after maturation for treatment and then release. The present study takes a novel approach of exposing immature adult male Queensland fruit flies (Bactrocera tryoni, or 'Qfly') to raspberry ketone (RK) mixed in food, forcing these flies to ingest RK at ages far younger than they would naturally. After feeding on RK-supplemented food for two days after emergence, male Qflies exhibited a reduction in attraction to cuelure traps that lasted more than 20 days. This approach to RK exposure is compatible with current practises, in which Qflies are released as immature adults, and also yields advantages of accelerated reproductive development and increased mating propensity at young ages