Protect your garden from the Queensland Fruit Fly

Published on 30 March 2020

Queensland fruit fly

The Queensland Fruit Fly (QFF) is a year-round horticultural pest for local gardeners and producers. As sunset temperatures exceed 16 degrees in spring, flies begin laying eggs in many commonly grown fruit and vegetables suitable for hosting. Flies remain active during summer and autumn, even surviving over winter by sheltering in buildings and trees.

Common host fruit

All stone fruits, apples, peaches, pears and tomatoes are common garden fruits that are susceptible, but so are fruits like capsicums, chiles, loquats, persimmons and pomegranates.

Confronting flies in your garden

Agriculture Victoria provides a full resource guide on the QFF lifecycle, appearance descriptions and host fruits commonly found in gardens.

Measures you can take

Make a fly trap

Cut 3 coin-sized holes in a 1.5L bottle about 10cm from the cap. Add in 3 cups 100% pulpy fruit juice and 3 tablespoons of cloudy ammonia until bottle is half full. Tie string around bottle neck and hang from a tree 1-1.5m above ground. Change mixture weekly for best effects.

This method is effective year round.

Net your trees

Make a frame from PVC tubes or stakes to surround your trees. Drape UV stable mesh over frame all the way to the ground
. Be sure that no fruit is touching the netting as flies are able to lay eggs through gaps.

This method is effective year round.

Bag your fruit

An alternative to netting a whole plant, you can tie recycled plastic bags or sleeves over the fruit you want to keep. Make sure there are no gaps for flies to enter. Remove and destroy any un-bagged and unwanted fruit.

This method is effective in summer to autumn.

Spray and bait

Apply a spray or gel (available from a nursery or hardware store) to trunks and foliage of plants, but not the fruit. Flies will be attracted to bait and be poisoned by insecticide.

Spray insecticide onto foliage and developing fruit, or as directed by the product. Always read warning labels of pesticides

This method is effective in spring to autumn.

Inspect your fruit

Regularly check your ripening fruit for sting marks or discolouration. Remove and destroy any fruit showing signs of infestation, and make sure you keep your garden free from any unwanted, rotten or fallen fruit. 
Remove any flowers or fruit you are not actively protecting.

This method is effective year round.

Prune your apricot tree

It is important to prune your apricot trees at least once a year.

Removing unhealthy or unnecessary branches

  1. Cutting off dead, diseased, damaged or competing branches.
  2. Removing small sprouts growing out of the trunk or branches.Cutting off branches that grow straight down or towards middle of the tree.

Thinning out the branches

  1. Choose a few healthy scaffold branches that you want to keep.
  2. Cut off most of the remaining branches about 0.6 cm above where they connect to the trunk and thinning out the entire tree.
  3. Prune branches located within 20–25 cm of your scaffold branches.

Watch a demonstration video on shortening the remaining branches.

Already affected fruit

Do not compost infested fruit: put it in a plastic bag and leave in the sun for a week, then put it in your garbage bin. Larvae will spawn in your compost if you put it in there.

Alternatively, you can bake, boil or microwave your fruit at high temperature for a few minutes to destroy eggs and larvae.

Queensland Fruit Fly lifecycle

There are 4 stages in the life cycle that you should be aware of.

Egg: 1 female can lay up to 100 eggs per day inside host fruits and vegetables.

Larva: after hatching, maggots begin eating fruit from within, causing it to rot and fall to the ground.

Pupa: it chews its way out of the host fruit and burrows into the soil where it forms a pupal case around itself and begins its transformation into adult form.

Adult: it emerges from the ground, begins feeding, then mating and searches for a suitable fruit to lay eggs in.

In the right conditions, the Queensland Fruit Fly can complete its lifecycle in around 30 days, potentially allowing for 9 generations per year.

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