Managing Queensland Fruit Fly

Published on 15 February 2024

We’ve been hearing a bit about the problem of Queensland Fruit Fly lately and we know it has managed to get into fruit trees across a number of our small towns. Be in no doubt it is a serious pest for both home gardeners and commercial growers. Queensland fruit fly attacks a wide range of fruits and fruiting vegetables, leaving them inedible. So it is really important that people are pro-active in dealing with the problem. It is also unlikely that on single thing will solve the fruit fly problem – so it does need to be a multi-pronged approach.

Queensland fruit fly populations usually increase in spring as temperatures rise, but they can remain active in autumn and winter if warm weather persists and suitable host produce is available. But they can survive cold winters by taking refuge in sheltered areas and can continue through their life cycle if the weather is warm enough and suitable hosts are available.

In an established garden, the first thing to consider are physical barriers to prevent the fruit fly getting in. and laying eggs inside your fruit and vegetables.

There are a variety of good options for insect proof netting and many people will have to prevent birds getting to fruit anyway. Drape fine, UV stable mesh over trees or frames made from PVC tubes or stakes to protect fruit after pollination has occurred. Secure nets around the base of the trunk or to the ground to prevent flies from getting inside. Any fruit touching the netting may be stung by Queensland fruit fly, so it’s important to avoid direct contact.

Another option is bags and sleeves– when fruit have set, place bags or sleeves over the fruit you want to keep. Secure them to the plant using tie wire, clothes pegs or string, ensuring there are no gaps where Queensland fruit fly can enter.

Practise good garden hygiene- a basic rule for any disease or pest prevention – make it as hard as possible for them to get a foothold. Keep your garden free from unwanted, fallen and rotten fruit to remove potential breeding spots.

Pick and use fruit or vegetables as they ripen or harvest the produce early if it will ripen after it's picked.

Think about how you garden.
You might also want to think about the types of fruit trees you and what will best suit your ability to deal with fruit fly. For example choosing dwarf varieties of fruit trees which are easier to cover with netting and to inspect for damage may be a good option.

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.
Just remember how you manage your garden for pests like fruit fly will impact your neighbours as well.

Once you have fruit fly in your fruit…
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 Queensland fruit fly and prevent spread to other areas:

• seal fruit or vegetables inside a plastic bag and leave it in the sun for at least 14 days
• sealing fruit inside a plastic bag and place it in a freezer for 2 days, or
• microwave or boil unwanted fruit or vegetables to kill any maggots.
• You can then discard the bagged, treated fruit or vegetables in your rubbish bin.

A good way of monitoring your garden for Queensland fruit fly activity by:

• Installing traps to monitor Queensland fruit fly activity in your garden
• Regularly inspecting ripening fruit and vegetables for signs of Queensland fruit fly. Fruit infested with Queensland fruit fly can appear in good condition from the outside. Look for sting marks on skins and cut open fruit and vegetables to check inside for maggots.

If you notice fruit flies, or Queensland fruit fly eggs or maggots, you'll know that you need to act fast to control them.
Traps can be used to monitor and reduce adult Queensland fruit fly numbers. Traps used for monitoring are referred to as ‘male only’ traps.
If you have Queensland fruit fly in your garden, use a trap that catches both female and male flies. These traps contain a protein to lure Queensland fruit flies into the trap, where they are killed using an insecticide or liquid.

Make your own Queensland fruit fly 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 per cent 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.
Bait sprays or gels combine a Queensland fruit fly food attractant with an insecticide to attract and kill Queensland fruit fly. Baits are usually spot-sprayed onto the trunk and foliage of host plants (not the fruit).
Adult Queensland fruit flies are attracted to the bait as a food source and are killed by eating the insecticide.
Insecticide sprays can be harmful if used incorrectly, so always read the and follow the label directions. Make sure the withholding period has passed before picking treated fruit or vegetables and be sure to wash them well before eating them.
One of the most frustrating thing for a lot of people is seeing trees on neighbouring not being looked after or neglected. If it is on public land then contact the land manager. You may need to contact you neighbour to let them know there is a problem and advise them to get appropriate advice.