Information for gardeners
Controlling Queensland fruit fly in home gardens
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.
Queensland fruit flies are known to survive cold winters by remaining in the soil and emerge as adults as temperatures increase, when they can fly and mate. The female fruit fly then feeds on a source of protein to produce eggs and searches for a suitable host to sting and deposit her eggs. If she is successful, the eggs hatch into maggots that feed on the ripening fruit, which is inedible.
If left uncontrolled, Queensland fruit flies can destroy crops.
Here are the steps you can take to manage this pest.
Determine if you have Queensland fruit flies, using pheromone based traps. These traps contain female fruit fly odours, which attract males, and an insecticide that kills them. These traps indicate if fruit flies are active in your area and when you need to act.
Regularly inspect produce for maggots, which are 5-10 mm long and creamy-white in colour. To check for maggots, cut open ripe fruit because infested fruit may appear in good condition from the outside.
Queensland fruit fly maggots in a peach.
Also, check for small puncture marks called stings on fruit skins. Stings show where the female fruit fly has laid her eggs and prematurely ripened fruits.
A tomato with a fruit fly sting on the skin, shown as a halo surrounding a dark circle, and a maggot in the fruit.
If Queensland fruit flies are in your garden, combine monitoring with several management strategies to control this pest.
Traps are designed to lure and kill adult fruit flies. Some traps are used to monitor Queensland fruit fly numbers only, indicating if fruit flies are active in your area and when you need to act. These traps are often referred to as male only traps. Other traps control Queensland fruit fly populations by catching females as well as males.
If Queensland fruit flies are in your garden, you will need to actively control these populations with a trap that can catch females as well as males. These fruit fly traps contain a protein which attract females then kills them. Follow the product instructions how set up and place the traps. Fruit fly traps are usually placed in host trees, but they can also be placed around the garden to draw fruit flies away from your produce.
Lynfield trap used to attract and kill fruit flies.
You can also make your own traps using an empty soft-drink bottle (with lid). Please note that these traps may attract both pests and beneficial insects.
Cut three holes in the empty soft-drink bottle about the size of a 10 cent piece, 10 centimetres from the top. Add the bait mixture: one cup of 100 per cent fruit juice (including pulp) and one 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, 1.0-1.5 metres off the ground. The mixture can last up to three weeks, but should be changed weekly for best results.
It's important to maintain good hygiene in the garden. Follow these steps to protect your produce.
Remove unwanted fruit and vegetables
Pick and use fruit or vegetables as they ripen, and don't leave them on the plant for fruit flies to attack. Collect and destroy any rotting or unwanted host produce, whether it is on the ground or on the plant, to reduce the risk of fruit fly maggots developing.
Do not put untreated produce in your compost or worm farm as this will aid the Queensland fruit fly life cycle. Also, do not dispose untreated produce directly into your rubbish or green bin, as it may cause a new infestation in another area.
Microwave unwanted fruit or vegetables to kill any maggots. Alternatively, place produce in a plastic bag, seal the bag and either leave it in the sun for 5-7 days or place it in a freezer for two days. The bagged, treated fruit or vegetables can then be discarded in your rubbish bin.
Bagged, unwanted oranges exposed to the sun.
Prune and remove unwanted host plants, and replace with alternative plants
Host fruits on fruit trees often ripen at the same time, producing loads of fruit that must be harvested quickly. If you wish to keep these fruit trees, prune them to a manageable size so you can reach the produce easily. Also reduce the size of the tree so it does not produce more fruit than you need.
Remove any unwanted or neglected host trees on your property and replace them with non-host alternative plants such as local wattles or grevilleas . This will reduce the risk of Queensland fruit fly attacking your produce and also remove potential breeding sites in your area.
Harvest produce early
If possible, plant early-maturing host fruit and vegetables and/or harvest the produce early if it will continue to ripen after it is picked. Harvesting prior to ripening removes fruit from trees before female Queensland fruit flies can lay their eggs. Planting fruits that are harvested in late Spring and early Summer also removes host material before Queensland fruit flies have had time to build up their populations to damaging numbers.
Use physical barriers to stop female Queensland fruit flies laying eggs in your produce.
Cover fruit trees with very fine UV stable mesh netting over a frame, using PVC tubes and stakes as a frame. Alternatively, use an outdoor gazebo with zippers as it is easier to inspect trees and harvest fruit when it ripens. Depending on the produce, you may need to install nets when fruit begins to develop so insects can pollinate flowers early in the season. All nets should be secured around the trunk base or to the ground to protect your crop.
If you have had a fruit fly infestation previously, fruit fly pupae may be in the ground under your fruit trees. In this situation, secure the bottom of the net to the trunk base to stop any adult fruit flies emerging from the ground to inside the net. If they are inside the net, Queensland fruit flies can infest your crop.
Bags and sleeves
When fruit begins to develop, place bags and sleeves over the fruit you wish to keep. Remove any flowers or developing fruit from the plant that are not covered by the barrier. Secure bags and sleeves to the plant with tie wire, clothes pegs or string.
Nets, bags and sleeves can be purchased from nurseries and home garden retailers.
Baits are an insecticide that is mixed with a Queensland fruit fly food attractant. They are usually spot-sprayed onto the trunk and branches of host plants, which the pests feed on while they are in the tree canopy. These treatments are often used to reduce Queensland fruit fly numbers in an area. Baits can be purchased from nurseries and home garden retailers.
Insecticides which are usually applied to leaves and developing fruit can kill adult Queensland fruit fly on contact or destroy eggs and larvae in fruit, depending on the insecticide. They can be purchased at nurseries and home garden retailers.
As insecticide sprays can be harmful if used incorrectly, always read the label and follow the instructions. Also, make sure that the withholding period has passed before picking treated produce and always wash treated fruit or vegetables before eating them.
Please note that insecticide sprays can kill beneficial insects in the garden and repeated use can cause insecticide resistance.
For more information about fruit fly management, visit the Prevent Fruit Fly website.
Protecting other areas from Queensland fruit fly
The best way to prevent QFF from spreading to other areas is to not travel with QFF host fruits or fruiting vegetables. The highest risk of introducing QFF into other areas is by taking home grown fruits into those areas. Home grown fruits have a much higher chance of being infested with larvae than store-bought produce.
Heavy fines apply if you are caught travelling with QFF host produce into the Greater Sunraysia Pest Free Area. Restrictions also apply to carrying fruit fly host materials into some other states and territories. More information is available from the Australian interstate quarantine website.