Tephritid fruit flies

Reproductive biology, Ecology and Management of Tephritid fruit flies

Tephritid fruit flies are the world's most devastating insect pests of horticultural crops and in many regions the Sterile Insect Technique (SIT) is used to combat outbreaks or to suppress residual populations. In SIT, millions of flies are reared in large factories, sterilized (usually with gamma radiation), and released into nature. The released males then mate with wild females. Eggs fertilized by the released males fail to develop, and so the pest numbers are reduced in the next generation. This method can greatly reduce the need for environmentally and medically hazardous pesticides. Basic ecology and reproductive biology are at the very core of SIT and so basic research on the ecology, sexual and reproductive biology of tephritid flies has very applied benefits. This is one of the main emphases of research in the BBRG.

As a community service, we maintain the Australian Fruit Fly Listserver to facilitate communication amongst researchers, industry groups and administrators with an interest in the biology or management of tephritid fruit flies. It is free and is used to disseminate information about upcoming meetings, recent publications, new methods, new policies, funding opportunities, scholarships etc. For information about the listserver, contact Phil Taylor.

Fruit fly exclusion Zone (FFEZ)
(click to download)

Female Queensland fruit fly ('Q-fly')

Female Q-fly on an orange.

Ecological Competence of Queensland fruit flies

Ecologicial competence is an extremely important factor to consider when investigating the likelihood of outbreaks in endemic areas, likelihood of outbreaks or population establishment in new areas, and the potential of SIT to quell wild populations. For SIT to be effective, the released males must survive in the field, attain sexual maturity, and then compete sexually with their wild counterparts. In the laboratory, with ideal conditions and ample food, wild Q-flies mature sexually 2-4 weeks after emerging and mass-reared sterile flies mature sexually 7-10 days after emerging. This is quite a while to survive the field before even entering the mating arena. Are mass-reared sterile flies that are released for SIT able to meet the behavioural challenges of finding food and moisture, avoiding predators, dispering, and choosing appropriate microhabitats? Are they able to meet physiological challenges of maintaining energetic, nuritional, temperature and hydration homeostasis and tolerating stress? Q-flies are found across a wide range of climates on Australia's eastern coast, from the constantly warm and humid conditions of northern Queensland, through the moderate temperate and humid conditions of New South Wales and south to the cool winters and hot, dry summers of Victoria. This wide range may indicate a highly flexible fly or local adaptation.

This research has supported by Horticulture Australia Ltd with contributions from numerous fruitgrowing industries.

Participants: Chris Weldon (Macquarie University) and Phil Taylor (Macquarie University).

Q-fly mass-rearing facility at
Elizabeth Macarthur Agricultural Institute

Field cages to test sexual and ecological
performance in semi-natural conditions

At dusk, males 'call' to sexually receptive
females with pheromones and songs

Pre-copulatory sexual processes

Tephritid fruit flies have interesting and diverse sexual biology. In many species, males aggregate and call for sexually receptive females with pheromones produced by anal glands and with songs generated by rapid wing fanning. Courtship in these flies is a multi-modal presentation of visual, acoustic and olfactory signals. Female fruit flies are very choosy about their sexual partners, with certain males gaining many copulations and the vast majority gaining few or none. Who are these sexy males? How do they achieve their success? What do females gain from their preferences? These questions are central to understanding the Queensland fruit fly mating system and are also central elements to the assessment and improvement of flies used in SIT. If wild females can detect differences between released and wild males, they may then reject released males as mates and SIT will not be effective. Further, even if only slight differences exist between released and wild males, and if females have poor abilities to discriminate these differences, selection on females will likely lead to increased ability and tendency to discriminate against released males over generations (i.e., behavioural resistance). We are currently working on identifying male characters that are associated with success at acquiring mates (e.g., size, age, nutrition, acoustic calling and courtship displays). This work has been featured in The Macquarie Researcher.

This research has been supported by Australia & Pacific Science Foundation and Horticulture Australia Ltd.

Participants: Phil Taylor (Macquarie University), Diana Perez-Staples (Universidad Veracruzana, Mexico), Chris Weldon (Macquarie University), Cathy Smallridge (SARDI Entomology), Andrew Jessup (I&I NSW DPI), and Richard Mankin (USDA-ARS).

N-3-Methylbutylpropanamide (C8H17NO), a major
component of Q-fly pheromone (see Pherobase)

Male Q-fly calling song
(click to listen)

Male Q-fly courtship song
(click to listen)

Post-copulatory sexual processes

In addition to complex and interesting pre-copultory processes, tephritid fruit flies also tend to have quite elaborate post-copulatory processes which may further winnow down the pool of successful males. There is far more to sexual success than securing lots of copulations. Copulations may vary dramatically in their translation to fertilizations. For example, females may store vast numbers of sperm after copulating with some males, and few or none after copulating with other males. Females may then remate after mating with certain males, exposing a first mate's sperm to competition. What male characteristics are related to post copulatory success - size? courtship behaviour? accesory gland fluids passed with the ejaculate? sperm quality? There is evidence that each of these issues may be important.

This research has been supported by Macquarie University Research Development Grants and Endeavour Awards.

Participants: Phil Taylor (Macquarie University), Diana Perez-Staples (Universidad Veracruzana, Mexico), Preethi Radhakrishnan (LaGuardia College, USA), Sam Collins (Macquarie University), David Raftos (Macquarie University), and Sham Nair (Macquarie University).

Copulating Q-flies

Abdomen of female and male Q-flies

Q-fly sperm

Irradiation and quality control for Q-fly Sterile Insect Technique

In the Sterile Insect Technique, millions upon millions of flies are reared in large factories, reproductively sterilized, and released into nature. The released males then mate with wild females. Eggs fertilized by the released males fail to develop, and so the pest numbers are reduced in the next generation. Use of this method can greatly reduce the need for environmentally and medically hazardous pesticides. We are currently carrying out a diverse research program designed to establish improved procedures for reproductive sterilization of Q-flies for SIT by gamma irradiation as well as to develop and fine-tune methods used to assess the quality of sterile flies used in SIT.

This research has been supported by Horticulture Australia Ltd and has been highlighted in Macquarie Research Active.

Participants: Sam Collins (Macquarie University), Phil Taylor (Macquarie University), Chris Weldon (Macquarie University), Bernie Dominiak (NSW DPI), and Connie Banos (ANSTO).

Q-fly pupae dyed with powder that transfers to
adults for identification of sterile flies in the field

GATRI cobalt 60 source used to irradiate Q-fly
pupae to induce reproductve sterility.

Post-Harvest Irradiation for Q-fly Disinfestation

A reliable method of quantifying irradiation damage is required for exporters/importers as live fruit fly life-stages may be detected at the destination of the fruit. There is no established method to confirm that an effective treatment had taken place which rendered the fruit fly specimens either unviable or sterile. This produces distrust and uncertainty between trading partners and produces a lack of a clear pathway to resolution. Again, the development of a reliable technology for this purpose would have huge implications for quality control of export fruit and quarantine of imported fruits. Furthermore, it would provide Australian producers with a production advantage and provide the basis for a standardised test that can be applied on a global basis. This proposal aims to address these two issues, that is, identification of wild vs irradiated SIT-release flies and determination of the status of live immature fruit fly intercepted in fruit thought to have been irradiated. We propose to achieve this by correlating the level of irradiation of fruit flies with molecular data, physiological and phenotypic data (related to quality control of adult flies), in order to produce a quick and reliable test to confirm irradiation and predict biological outcomes. The research will draw together scientists with experience in fruit fly irradiation and quality control, insect physiology, SIT and molecular/cell biology.

This research is currently supported by Horticulture Australia Ltd, with matching funds from AusVeg and Bowen District Grower's Association.

Participants: Wayne Leifert (CSIRO), Richard Glatz (SARDI), Sabbir Siddiqui (University of Adelaide), Michael Fenech (CSIRO), Sam Collins (Macquarie University), Phil Taylor (Macquarie University).

Male Annihilation Technique (MAT) for Q-fly suppression

With recent restrictions on the use of organophosphate insecticides, improved alternative methods for the control of Qfly are needed. Lures used to attract Qfly are critical for the Male Annhialation Technique (MAT), and are hence important for area-wide management. Cuelure is the most effective current lure for male Qfly, but is a ‘poor cousin’ of more attractive tephritid lures such as methyl eugenol that are available for some other fruit flies. Development of more attractive lures for Qfly will allow more aggressive and reliable deployment of MAT. Further, cuelure is thought to perform poorly in dry environments, and so assessment of how climatic conditions affect efficacy and 'active space' of cuelure and related molecules is essential for development of effective deployment protocols across Australia's diverse climate zones and seasons. For more reliable performance of MAT we need lures that can perform better than cuelure in dry environments. Recent research has derived new molecules that show outstanding potential as Q-fly lures. 

This research is currently supported by Horticulture Australia Ltd.

Participants: Phil Taylor (Macquarie University), Matt Siderhurst (Eastern Mennonite University), Ian Jamie (Macquarie University).