The Queensland fruit fly (QFF) is Australia's number one horticultural pest, attacking a wide range of fruits and fruiting vegetables. Commercial growers need a trap to catch mated female fruit flies which can lay hundreds of eggs in their lifetime, infesting host produce and threatening access to domestic and international markets.
The good news is that researchers are taking a multidisciplinary approach to address this problem.
Here is an overview of Queensland fruit fly research conducted by Agriculture Victoria Research in collaboration with scientists from Queensland University of Technology, Stockholm University, CSIRO, Plant Biosecurity CRC, NSW Department of Primary Industries, South Australian Research and Development Institute, Biofly, Wine Australia and Summerfruit Australia.
Attract and kill traps
Fruit fly traps contain attractant odours that lure adult flies into a trap and then kill them using an insecticidal bait. These 'attract and kill' traps are predominantly deployed to monitor male Queensland fruit fly populations in the field so product users can identify hot spots and take action. Another commercially available fruit fly trap contains a protein bait, which attracts young, unmated female flies. But an effective lure for mated female Queensland fruit fly remains elusive.
Agriculture Victoria Research scientists at AgriBio are developing a novel female Queensland fruit fly attractant through a Plant Biosecurity CRC-funded project in collaboration with Summerfruit Australia (building on a Hort Innovation summerfruit project). The attractant is based on a mixture of chemicals common to ripening fruits, which is showing promise in field trials. Because the female fruit fly is swamped with fruit odours in an orchard, the attractant needs to be a super smelling scent to stand out. Therefore, the team's complex designer blends will contain a mixture of synthetic fruit odours, microbial volatile organic compounds and insect pheromones.
AgriBio scientists and their regional colleagues at Agriculture Victoria Research centres in Tatura and Mildura have been testing Queensland fruit fly attractants, and extensive field trials are planned for 2017-2018 to further improve and evaluate the new lures. The team is also assessing the effectiveness of different protein bait traps used for Mediterranean fruit fly and Queensland fruit fly to see if a single lure could be developed for both species of fruit fly for use in Australian surveillance systems.
Agriculture Victoria Research entomologists based at Tatura are also collaborating on the adaptive area wide management of Queensland fruit fly using SITplus. This project is being delivered by Hort Innovation - with support from the Australian Government Department of Agriculture and Water Resources as part of its Rural R&D for Profit program - and CSIRO. Scientists are researching when adult Queensland fruit flies emerge from fruit that was infested in autumn. They aim to determine if flies caught in traps during spring result from adult flies that survived winter in refuges around buildings and windbreaks, or flies freshly emerged from pupae in the soil. This study has the potential to change how Queensland fruit fly is managed over large areas.
The Plant Biosecurity CRC is developing molecular diagnostic tools to identify pest and non-pest fruit fly species from Australia and overseas. Scientists will be able to build on what is known about tephritid fruit flies, which comprise over 600 species (including Queensland fruit fly), and rapidly identify insects in traps by their DNA. This will greatly assist with efforts on the ground to detect fruit fly species and improve market access of produce that is susceptible to fruit fly.
There are various insects that are natural enemies of fruit flies and feed on them at selective stages of their life cycle.
Scientists at AgriBio and QUT are focussing on parasitoid wasps, which hunt for insect eggs and larvae. A braconid wasp has been identified as a suitable predator for Queensland fruit fly, and mass rearing techniques for this insect have been developed. The wasp is already present in Australia and has an elongated egg laying device called an ovipositor, which it uses to probe fruits and inject eggs into the larvae of fruit fly. When the egg hatches, the braconid wasp develops inside the fruit fly maggot, killing its host.
Boosting wasp numbers could potentially help control Queensland fruit fly numbers as part of an integrated pest management strategy.
To control fruit fly numbers, it is critical to know which plant species the insects can use as hosts. The AgriBio team is exploring non-crop hosts that fruit flies might be using to bridge the gap between fruit growing seasons. In addition, there are several crop species that are not generally thought of as hosts, so the scientists are studying if these are in fact 'poor hosts' that allow fruit fly populations to survive when other fruits are scarce.
AgriBio scientists are using high-tech approaches to design and test their fruit fly lures. Fruit odours and insect pheromones are analysed using Gas Chromatography-Mass Spectrometry, DNA sequencing can identify microbes spread by fruit flies, odours are tested in a wind tunnel, and insect brain imaging and electrophysiology techniques are used to study insect behaviour and screen attractants in live fruit flies.
AgriBio scientists, together with a company in the US, are also conducting research on a portable, hand-held, electronic nose (E-nose) device that detects and identifies complex chemical odours in a similar way to the human nose. They are currently testing if the E-nose sensor can pick up specific odours emitted by fruit fly infested fruits. If this electronic device can consistently detect fruit fly maggots in host fruit, it could potentially be used to scan fruit before it is packed for market.