Tephritid fruit flies

Macquarie University in the SIT-Plus consortium

SITplus is a collaboration of research, regulatory and funding agencies that have joined forces to develop the use of Sterile Insect Technique (SIT) for the management of Queensland Fruit Fly, the most devastating insect pest of horticultural crops in eastern Australia. In SIT, millions of reproductively sterile flies are reared in large factories and released into the field. The released males then mate with wild females. Eggs of females mated 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.

Macquarie University joined the SIT-Plus consortium as a stakeholder in 2014, with other participants including Horticulture Australia Limited (HAL), CSIRO Biosecurity Flagship (CSIRO), Primary Industries Rural South Australia (PIRSA), South Australian Research & Development Institute (SARDI), Plant and Food Research Australia Pty Limited (PFRA) and NSW Department of Primary Industries (NSWDPI).

SITplus was formed to address the management of Queensland Fruit Fly as a result of the impact of the loss of the organophosphate insecticides (dimethoate and fenthion) that have been relied on for decades for management of Qfly and adaptation/climate change extending the boundaries of Qfly distribution in south-eastern Australia where they threaten the market access benefits that come from fruit fly freedom. The research of the consortium touches on all aspects of the Sterile Insect Technique, with current projects at Macquarie  focusing on development of larval diets that wuill be needed for factory-scale production of sterile flies.

For information on partner organizations, link to:

Horticulture Australia Ltd

CSIRO Biosecurity Flagship

Primary Industries and Regions SA (PIRSA)

South Australia Research & Development Institute (SARDI)

Plant & Food Research (PFR)

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. 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.

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.

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.