Queensland fruit fly facts

Fruit flies are one of the world’s most destructive horticultural pests and pose a major risk to horticulture industries around the world. There are over 4,000 fruit fly species in the world however only about 350 of these are of economic importance. There are more than 300 fruit fly species found in Australia, although only a few are considered to have an economic importance. The two main economic species being the Queensland fruit fly (Bactrocera tyyoni) and Mediterranean fruit fly (Ceratitis capitata).

In Australian Mediterranean fruit fly is an introduced species and is only found in Western Australia. It is not found in the greater Sunraysia region and it is important to ensure it is not introduced into the area.

Find out more about the Mediterranean fruit fly here.

Queensland fruit fly is an Australian native species that is endemic to Queensland. However it is now also found in parts of New South Wales, Victoria and the Northern Territory. South Australia, Tasmania and Western Australia are recognised as being free from Queensland fruit fly and maintain strict quarantine measures to protect this status.

Identify Queensland fruit fly

Knowing if the flies in your traps or larvae in your fruit is Queensland fruit fly or another species is critical to management. Queensland fruit fly is only very small but can be easily identified once you know what you are looking for. As with many insects, there are four stages in the life cycle of Queensland fruit fly: adult fly, egg, larva and pupa.

Adult Queensland fruit fly

Adult fruit flies emerge from the ground. They are generally between 5 to 8 mm long and are reddish-brown in colour, with distinct yellow markings.

They have a wing expanse of around 10 to 12 mm, and have clear wings with brown veins.

Females have an ovipositor (stinger) that is used to lay eggs into fruit.

You can identify fruit fly using this online tool from Plant Health Australia to help identify fruit flies.

Egg

Queensland fruit fly eggs are around 1mm in size, they are banana shaped and white in colour. As they are so small it is very hard to see the eggs. They are laid beneath the skin of host fruit, in batches of 6 to 12. Adult flies can lay up to 100 per day.

Larvae (maggot)

After about two days after the eggs have been laid in the fruit they hatch and small maggots emerge.

When the maggots first hatch they are very small, around 1 to 2 mm in size. As they start to feed on the host fruit they increase in size and a fully grown maggot is around 6 to 9 mm in size.

Maggots are creamy white/pale yellow in colour and when placed on a smooth surface they curl up and jump. Mature maggots chew their way out of the fruit (which has generally fallen to the ground) and burrow into the soil.

Pupae

Once maggots burrow into the soil they become pupa. Queensland fruit fly pupa are an oval shape, cream to brown, hard and are generally around 5 to 8mm long. The fly develops within the pupa.

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Understanding the life cycle

Knowing the life cycle makes it easier to control.

An adult female fly only needs to mate once and can lay up to 500-2000 eggs in its lifetime. It only takes a couple of minutes to lay 6-20 eggs in a host fruit.

These eggs can develop into adult flies in less than a month if the conditions are right. Because of the fly’s rapid breeding cycle, there can be multiple generations in one season resulting in exponential population growth.

Queensland Fruit Fly require warmth and moisture to complete their life cycle. Ideal conditions for development is around 26°C Extreme heat, frost and dry conditions will naturally reduce fly numbers but will not destroy all flies.

It is not clear how long flies can live in the wild but it is known that they are able to survive over winter suggesting they may live for at least 3 or more months.

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Behaviours of Queensland fruit fly

Fruit fly numbers tend to increase, usually in spring, when temperatures are warm and there is continued availability of suitable host plants. In spring when sunset temperatures exceed 16°C the adult flies that survived winter will mate and lay eggs into host fruits and vegetables.

Adult flies that reach maturation before winter set in will look for refuge from cold weather. As the day and night temperatures start to decline in autumn and early winter adult flies will move to warmer sites. Ideal areas for flies to survive the winter include evergreen trees such as citrus or native vegetation or man-made structures such as under the eaves of buildings.

The life span of the adult fly varies with the season. During the warmer months, flies will generally live up to two months. In the cooler months when they do not expend much energy. If they have a refuge from the weather they can live up to four months.

In the greater Sunraysia region Queensland fruit fly is generally active from August to May, though some activity will occur in warmer periods during the winter months.

Characteristics of adult flies:

Take about a week from emergence to reach sexual maturity.
Rest in shady trees (fruit trees, ornamental trees and shrubs) during the day.
Feed on bacteria that can be present on the host tree or adjacent plants.
Queensland fruit flies mate at dusk, when the temperature exceeds 16°C
Survive the cooler winter months in refuges.

Characteristics of female fruit flies:

Lay eggs into healthy, maturing and ripening fruit (on the tree) and vegetables
Feed on a source of protein before eggs will mature for laying
Reabsorb eggs during extended periods of cold weather
Lay up to 2,000 eggs in over 100 clutches over a period of up to 8 weeks.
Only need to mate once and produce up to 800 adult flies.
Are able to reabsorb eggs during winter to use as energy.
Females are able to mate a second time if necessary.

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Signs of Queensland fruit fly activity

Is my fruit infested?

Queensland fruit fly will only lay their eggs in fruit or vegetables that are still attached to the tree or plant. Start checking when your fruit or vegetables have reached their full size but before they show signs of colour change. Queensland fruit fly can lay eggs in fruit that is still hard and green.

How to check for Queensland fruit fly

Select fruit or vegetables from different sides of the tree/plant and different heights of the canopy.
Look for early ripening fruit or signs of damage.
Small black spots on the surface (sting marks) can be a sign of Queensland fruit fly infestation.
Carefully cut open the fruit with a sharp knife and look for larvae, they can be very small – 2mm when they hatch so you might need a magnifying glass to help look.

It is very important that you act very quickly when you have confirmed Queensland fruit fly. Remove all affected fruit from the tree and off the ground immediately to prevent the further increase and spread of fruit fly numbers.

Click here for advice on the best ways to dispose of infested fruit.

For tips for controlling fruit fly in your home garden click here

For advice on managing fruit fly in at commercial property click here