More than 300 species of fruit fly occur in Australia, although only a small number of these have any economic impact, with Queensland fruit fly (Bactrocera tryoni) and Mediterranean fruit fly (Ceratitis capitata) being the species of primary economic concern
It was the Queensland fruit fly (Bactrocera tryoni) that was detected in Tasmania in January 2018. As of 30 March 2019, the whole of Tasmania is once again fruit fly free.
Queensland fruit flies lay eggs in maturing and ripe fruit on trees and sometimes in fallen fruit. The maggots (larvae) hatch and the fruit is destroyed by the feeding maggots and by associated fruit decay. Queensland fruit flies can attack a wide range of fruit, fruiting vegetables and native fruiting plants. Evidence of Queensland fruit fly activity is sometimes seen as puncture marks (stings) in the skin of fruit. The stings are where the female fruit fly has laid her eggs.
Life cycle of the Queensland fruit fly
There are four stages in the life cycle of Queensland fruit fly: egg, larva (maggot), pupa and adult. Completion of the Queensland fruit fly life cycle is dependent on temperature and moisture.
Queensland fruit flies lay eggs in maturing and ripe fruit on trees and sometimes in fallen fruit. The stings that can be seen as puncture marks on the skin of the fruit are where the female fruit fly has laid her eggs.
The maggot (larva) hatches and the fruit is destroyed by the feeding maggots and by associated fruit decay. Mature larvae leave the fruit and burrow into the soil beneath the tree and form a hard, brown barrel-like shell from its skin, known as the pupa.
Queensland fruit fly adults emerge from their pupal cases in the soil and burrow towards the surface. There they inflate their wings and fly to find shelter, food and water. Then the cycle begins again.
Download the life cycle:
A mature Queensland fruit fly is around 6-8 mm long and is reddish-brown with some yellow markings.
You are more likely to see fruit fly maggots (larvae) than actual flies. Fruit fly larvae look like blowfly maggots. Mature fruit fly larvae are 8-11 mm in length and 1.2-1.5mm in width. They are usually easy to see in the flesh of the fruit.
Adult Queensland fruit fly
Female fruit flies lay eggs in maturing and ripe fruit on the tree. The skin of the fruit needs to be soft enough for the fly to pierce the skin with her ovipositor. Lesions in damaged fruit can also facilitate egg-laying. Queensland fruit fly eggs are generally hard to see as they are less than 1 mm long. Eggs are white in colour and banana-shaped.
A small creamy-white legless maggot emerges from each egg. When fully grown, larvae are about 8-11 mm long and creamy-white to pale yellow. Larvae tend to eat their way towards the centre of the fruit. Decay begins inside the fruit while the outside of the fruit may appear intact. The larvae tunnel into the fruit causing rotting, and so infected fruit often falls to the ground prematurely. Maggots continue to develop in fallen fruit, so infected fruit must not be disposed of in compost heaps.
Mature larva leave the fruit and burrow into the soil beneath the tree. Each larva forms a hard, brown barrel-like shell (puparium) from its skin. Inside this case the pupa develops into a fly.
Queensland fruit fly eggs
Copyright: Dr John Golding
Queensland fruit fly larvae
Copyright: Dr John Golding
Queensland fruit fly pupa
Copyright: DPI NSW
Queensland fruit fly female laying eggs
Photo: Dr John Golding
Queensland fruit fly adults emerge from their pupal cases in the soil and burrow towards the surface. There they inflate their wings and fly to find shelter, food and water. Under favourable conditions, adults are able to mate a week after emerging. Soon after mating, female flies are ready to lay eggs.
The female Queensland fruit fly has a retractable, needle-sharp egg-laying organ (ovipositor) at the tip of her abdomen. Using the ovipositor she digs a chamber about 3 mm deep in the outer layer of the fruit where up to 12 eggs are laid at a time.
Female QFF are capable of laying several hundred eggs during their lifetime. Adults can live for many weeks. Female flies usually mate once or twice. Male flies mate multiple times.
Queensland fruit fly behaviour
Typically adult Queensland fruit fly:
- are most active from dawn and the first few hours of the day and then towards late afternoon
- feed on a protein source to become sexually mature
- feed on a sugar source (honeydew, nectar) for energy
- rest during the day in shady trees (fruit trees, ornamental trees and shrubs)
- mate at dusk
Drosophila or vinegar flies
Vinegar Fly -
Unlike Queensland fruit fly, which infects fruit, Drosophila are commonly known as vinegar flies and have no significant impact on Tasmanian fruit production.
Adult vinegar flies are between three and four millimetres in length, half the size of an adult Queensland fruit fly.
Vinegar flies have dark tan bodies and bright red eyes, whereas the Queensland fruit fly has a reddish-brown body with very distinctive yellow stripes and spots.
They are often seen hovering over compost heaps and kitchen fruit bowls. Vinegar flies lay eggs in already damaged or rotting fruit that would not be harvested or eaten. They do not attack healthy, undamaged fruit.
Routine biosecurity measures continue around the State that contribute to protecting Tasmania from introduced pests and diseases, including:
- regular checking of the permanent fruit fly trap network across the State
- imposing strict requirements for the import of produce before it enters the State
- conducting targeted inspections of produce as it enters the State
- checking passengers, luggage, freight and mail at the border
Traveller's Guide webpage for further information on what you can and cannot bring to Tasmania.
Tasmania's biosecurity is a shared responsibility. Your help in being vigilant and obeying the strict import requirements is essential to protecting our industries, economy, environment and our way of life from the consequences of unwanted pest and disease incursions.
Reporting suspected Queensland fruit fly or suspect produce
If you see what you think may be signs of fruit fly contact Biosecurity Tasmania (03) 6165 3777.
You are most likely to see larvae in a piece of fruit, either fruit you have bought or fruit in your backyard. They look similar to blowfly maggots. If you are not sure, please report it anyway.
There are no costs involved in reporting and you would be performing an important public service in alerting us to anything that might be fruit fly.