Queensland fruit fly

1. Overview

Fruit flies are the world’s worst fruit pest. Fruit fly has the potential to threaten Australia’s horticultural industry.

Our region is particularly affected, with millions of dollars and hundreds of jobs at risk. Outbreaks in townships impact on growers’ ability to market and sell their produce, and there has been a recent dramatic rise in township outbreaks.

Swan Hill Rural City Council is partnering with local commercial fruit growers and the Department of Energy, Environment and Climate Action (DEECA) to control fruit flies in our region. We urge you to help reduce the threat that fruit fly poses to the region.

Fruit flies destroy fruit and vegetables grown commercially and in home gardens. Commercial growers have put strategies in place to control fruit fly in their crops, but they cannot control outbreaks in home gardens.

Video guides and fact sheets  

2. Understanding activity

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 fly are known to survive cold winters by taking refuge in sheltered areas. Queensland fruit flies can continue through their life cycle if the weather is warm enough and suitable hosts are available.

Fruit fly larvae (maggots) cause your fruit and vegetables to turn into a soft, mushy mess. Adult female fruit flies lay eggs in the flesh of ripening and ripe fruits and vegetables. Once the eggs hatch, the larvae feeds on the fruit, causing it to rot and drop to the ground. This damage will make your fruit inedible.

Just one fruit fly can cause an outbreak Female fruit flies can lay 500 to 800 eggs in their six month life. Fruit flies emerge, feed and mate in two to four days in summer and they hatch in just six to eight days.

This can translate in 700,000 flies in one season originating from just one fly.

3. Protect your produce

Using insect netting is the best way to prevent female Queensland fruit fly laying eggs inside your fruit and vegetables.

• Insect-proof netting – 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 (best if you have had Queensland fruit fly before) 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 between the netting and the fruit.
  Help sheet - Fruit fly exclusion netting
  
  (PDF, 10MB)
• 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.
  
  
• Outdoor gazebo with zippers – cover plants with an outdoor gazebo with zippers, which allow easier access to fruit.

4. Practise good garden hygiene

To reduce the risk of attracting Queensland fruit fly to your garden:

• 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.
• Choose dwarf varieties of fruit trees which are easier to cover with netting and to inspect for damage.
• 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.

5. Dispose of unwanted produce

Don't put untreated produce in your compost or worm farm because Queensland fruit fly will thrive under the warm and damp conditions and emerge as adults.

To stop the life cycle of Queensland fruit fly and prevent spread to other areas:

• microwave or boil unwanted fruit or vegetables to kill any maggots or seal fruit inside a plastic bag and place it in a freezer for two days until frozen solid.
• for large quantities of fruit, seal fruit or vegetables inside two garbage bags and leave in the sun for at least 14 days.

You can then discard the bagged, treated fruit or vegetables in your rubbish bin. Bagged fruit should not go into green waste bins because plastic is not acceptable in most green waste systems and to prevent any risk of live fruit fly going into green waste systems.

6. Monitor your garden

Monitor your garden for Queensland fruit fly activity by:

• Installing traps to monitor Queensland fruit fly activity in your garden (see ‘Traps’ below)
• 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.