About Fruit Fly

​​​​​​​​​​​​​There are around 14 species of fruit fly of potential economic concern on the Australian mainland. It was the Queensland fruit fly (Bactrocera tryoni) that was detected in Tasmania in January 2018.

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:

Appearance

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 1.2-1.5 ​mm in width. They are usually easy to see in the flesh of the fruit.

Adult Queensland fruit fly

Eg​gs  

​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. ​

Larvae (maggots)

​A small creamy white legless maggot emerges from each egg. When fully grown, larvae are about 6 to 8 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.​

Pupa​

Mature larva leave the fruit and burrow into the soil beneath the tree. Each larva forms a hard, brown barrel-like shell from its skin. Inside this case the pupa develops into a fly.​

Eggs

Queensland fruit fly eggs
Copyright: Dr John Golding

Larvae

Queensland fruit fly larvae
Copyright: Dr John Golding

​Pupa

Queensland fruit fly pupa
Copyright: DPI NSW

Adults 

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 flask-shaped 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 female laying eggs
Copyright: Dr John Golding

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 - Drosophila melanogaster
Copyright: Botaurus [Public domain], from Wikimedia Commons

Fruit flies are often confused with the small, dark brown Drosophila flies (commonly referred to as vinegar flies or ferment flies) that hang around ripe and decaying fruit. The Drosophila flies in Australia are not agricultural pests, but can be a nuisance where fruit and vegetables are stored. 













Information sourced from the NSW Department of Primary Industries

Contact

Fruit Fly Hotline
Report any suspected fruit fly to Biosecurity Tasmania
Phone: (03) 6165 3774

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