Controlling Queensland fruit fly in home gardens
The Queensland fruit fly (QFF) is a serious pest for both home gardeners and commercial growers. QFF attacks a wide range of fruits and fruiting vegetables.
You can manage QFF by monitoring QFF activity and using a range of methods to control this pest.
Watch this video to learn about:
- the life cycle of Queensland fruit fly (QFF)
- how it spreads
- how to monitor fruit and vegetables for signs of infestation and control numbers
[Narrator] Queensland fruit fly can be a problem for home gardeners and commercial growers because it attacks a large variety of fruit and vegetables, making them inedible. Queensland fruit fly spreads from infested plants to nearby fruit and vegetables, and by people sharing or travelling with home grown fruit or vegetables. While fruit and vegetables may look fine from the outside, they may be rotten or have eggs or maggots hidden inside.
So what do Queensland fruit flies look like? Adult flies are approximately seven millimetres long and are reddish-brown in colour, with distinct yellow markings. Queensland fruit fly goes through four main stages of life.
The adult female Queensland fruit fly injects her eggs into host fruit, laying up to 100 eggs a day. Eggs are white and one millimetre long, which makes them hard to see. You may see tiny puncture marks in fruit.
The eggs hatch into creamy yellow maggots that grow up to nine millimetres long. The maggots feed on the fruit, eventually chewing their way out. The maggots then burrow into the ground and change into oval, brown, hard pupae. After a few weeks, if conditions are suitable, the fruit flies come out of the ground and look for food around gardens.
After feeding and mating, females search for suitable ripe fruit to lay their eggs into, and their cycle continues.
So, if you want to grow fruit and vegetables in your garden, check for Queensland fruit fly and take steps to manage it before it spoils your produce or spreads to other properties.
So, to protect your garden, hang traps to monitor and catch Queensland fruit flies, apply baits and cover sprays to control Queensland fruit flies, pick up and dispose of fallen fruit, remove unwanted fruiting trees and vegetables, and net host fruit and vegetable plants.
Monitor your garden for fly activity
Monitor your garden for Queensland fruit fly activity by:
- installing traps and lures
- regularly inspecting produce
If you notice fruit flies, or QFF eggs or maggots, you'll know that you need to act fast to control them.
Install traps and lures
Lures contain a mixture of female fruit fly pheromone that attracts males, and an insecticide that kills them.
Male-only traps are for monitoring QFF numbers only and aren't effective for controlling QFF population. Check your lures regularly.
Inspect your produce
Fruit infested with QFF can appear in good condition from the outside, so regularly cut open ripe fruit to check for maggots. You might also notice small puncture marks on fruit skins from where the female fruit fly has laid her eggs.
Trap and kill flies
Traps are designed to lure and kill adult fruit flies. If QFF are in your garden, you'll need to actively control these populations with a trap that can catch females as well as males.
Fruit fly traps are usually placed in host trees, but they can also be placed around the garden to draw QFF away from your produce.
Make your own traps
You can make your own traps using an empty soft-drink bottle and lid and homemade bait. Note that these traps can also attract insects that are good for your garden.
- In an empty soft-drink bottle, cut three holes about the size of a 10 cent piece, 10cm from the top.
- Add the bait mixture to the bottle. Pour in 1 cup of 100% fruit juice (including pulp) and 1 tablespoon of cloudy ammonia (or wheelie bin cleaner).
- Tie a string around the neck of the bottle and hang it from the tree in the shade, 1m to 1.5m off the ground.
The mixture can last up to 3 weeks, but should be changed weekly for best results.
Practise good garden hygiene
To reduce the risk of attracting QFF to your garden:
- Pick and use fruit or vegetables as they ripen or harvest the produce early if it will ripen after it's picked.
- Reduce the size your trees so they don't produce more fruit than you need.
- Remove any unwanted or neglected host trees and replace them with early-maturing host plants or non-host alternative plants such as local wattles or grevilleas.
- Collect and destroy any rotting or unwanted host produce, whether it's on the ground or on the plant.
Dispose of unwanted produce properly
Don't put untreated produce in your compost or worm farm, or directly into your rubbish or green bin.
To stop the life cycle of QFF and prevent spread to other areas:
- microwave unwanted fruit or vegetables to kill any maggots
- place the produce in a plastic bag, seal the bag and either leave it in the sun for 5 to 7 days or place it in a freezer for 2 days
You can then discard the bagged, treated fruit or vegetables in your rubbish bin.
Use nets and bags to protect your produce
Physical barriers can stop female QFF laying eggs in your produce. Some options include:
- tree nets, using PVC tubes and stakes as a frame
- bags and sleeves, using tie wire, clothes pegs or string to secure them to the plant
- outdoor gazebo with zippers
If you've had an infestation before, there might be pupae in the ground under the plants. In this case, use bags and sleeves or secure the tree nets to the trunk base instead of the ground.
If there are flowers or developing that are not covered by the barrier, remove them from the plant.
Depending on the produce, you might need wait until fruit begins to develop to install nets so insects can pollinate flowers early in the season.
Baiting and insecticides
Baits are an insecticide mixed with a QFF food attractant. Spot-spray baits onto the trunk and branches of host plants. QFF will feed on them while they're in the tree canopy.
You can spray insecticides on leaves and developing fruit to kill QFF. Depending on the insecticide, it might kill adult flies on contact or destroy eggs and larvae in fruit.
Misuse and overuse of insecticides
Insecticide sprays can be harmful if used incorrectly.
They can also kill insects that are good for your garden and repeated use can cause resistance in pests.
- Always read the label and follow the instructions.
- Make sure the withholding period has passed before picking treated produce.
- Wash treated fruit or vegetables before eating them.
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