Diverse flies in a complex landscape
Of the nearly 100 fruit fly species in Australia, 10 are pests and their pest status varies. Many more species are found overseas. Ability to efficiently and accurately identify fruit flies is key to biosecurity decision-making. We are developing reliable molecular diagnostic markers for Bactrocera fruit flies for use in Australia's biosecurity monitoring.
Fruit flies are widely believed to be native to rainforests, but are instead found more often in agricultural or urban areas where they can breed on commercial, non-commercial and native fruits. To effectively control fruit flies, there is a need to understand fruit fly requirements for survival and reproduction, and how fruit flies move across landscapes. We are developing ecological knowledge of the Queensland fruit fly, and other Australian fruit fly pests, for effective Area-Wide Management.
Non-commercial fruit trees are often seen as the source of incursion into nearby commercial orchards and providing havens that are isolated from active management. However, data to support a central role of non-commercial fruit remains scant. We are mapping fruit resources across landscapes and estimating the relative role of commercial and non-commercial fruit as contributors to fruit fly pest populations. This information will inform decisions of whether, when and to what extent pressure on commercial crops might be ameliorated through local management of non-commercial fruit.
Historical approaches to fruit fly management have relied heavily on insecticide cover sprays that coat the tree and the fruit with a toxic barrier. Insecticides are commonly toxic to operators, as well as posing additional risks to consumers, non-target organisms and the environment. As an alternative to cover sprays, we are examining ways of attracting the flies to the toxic baits and traps (‘lure and kill’ technology). By this approach, insecticides are contained and isolated from users, crops and the environment. We are developing new insect attractants for use in lure and kill devices, focusing especially on pheromones that are used by fruit flies to locate potential mates and bacteria that are used by fruit flies to locate food and hosts.
Rather than luring flies to toxic baits, an alternative behavioural approach instead aims to repel fruit flies from crops. We are investigating chemical cues that fruit flies tend to avoid, including natural products produced by their predator enemies such as spiders and ants, as a starting point for new products that protect crops through repellence rather than toxicity.
Novel microbial control
Fruit flies are vulnerable to parasitoids and pathogens that can be used for biological control including parasitoid wasps, viruses, bacteria, fungi and nematodes. However, with availability of highly effective synthetic insecticides such ‘soft’ tools have remained underdeveloped and under exploited in fruit fly management. With growing restrictions on use of synthetic insecticides, we are now exploring the potential impact of natural enemies and entomopathogens on fruit fly pest populations.
Pathogens are an important emerging source of active ingredients as ‘biopesticides’. We are investigating the potential of nematodes, fungi and bacteria for the development of novel biopesticides for use against Australian fruit fly species, especially during the soil-dwelling pupal stage.
Some bacteria are important pathogens, and can help to control fruit fly populations by killing or reducing health of their host. One bacteria, Wolbachia, has a more subtle and complex effect that potentially supports an alternative management pathway. Wolbachia is passed from mother to offspring and can induce sterility when an infected fly mates with an uninfected partner. This relationship can potentially be exploited through an ‘Incompatible Insect Technique’ (IIT), whereby sterility is induced in pest populations through the release of Wolbachia-infected male flies. Such approaches have shown potential in some insects, and we exploring whether such approaches might be effective for major fruit fly pests in Australia.