Managing Queensland Fruit Fly in home gardens
Have you found maggots in your produce? Gardeners from across Naarm/Melbourne are now reporting the presence of Queensland Fruit Fly (QFF). These devastating horticultural pests attack a wide range of common fruit and fruiting vegetables including apples, pears, stone fruit, feijoas, tomatoes and capsicums and pose a significant risk for local farmers. We encourage all home gardeners to learn to identify and actively respond to this pest.
How to recognise Queensland Fruit Fly
An adult QFF is 5-10mm, with a yellow band. Small flies hovering around a compost bin or fruit bowl are sometimes described as ‘fruit flies’ but are not Queensland Fruit Fly (Bactrocera tryoni). Codling moth larvae share many host species are also sometimes mistaken for fruit fly.
Queensland fruit fly adult. Actual size is 5-10mm. (Image courtesy of Agriculture Victoria)
Adult QFF with 20C for sale
Larvae (maggots) develop inside the fruit which are a cream-white colour and grow to 10mm or about the size of a grain of rice. Fruit may not appear damaged on the outside, so cut fruit open to check. Mature larvae burrow into the soil where they pupate and emerge as adult flies in warm weather.
When QFF larvae are fully developed they can ‘jump’ small distances on a hard surface.
I’ve found QFF in my garden. What should I do now?
If you’ve found QFF there are some important steps you should take to protect your garden as well as other gardeners and farmers:
- Check all susceptible crops for signs of egg-laying marks and/or larvae. Be suspicious of the earliest ripening fruit in each crop, as insect damage often hastens the ripening process. Clear any fallen fruit from under susceptible plants that could contain larvae.
- Kill the larvae by heating (in plastic bag in sun during hot weather for a week, or boiling) or freezing affected produce for a few days before disposal. Do not put untreated produce in compost, organics or waste bins as this will facilitate further spread.
- Let your neighbours know that you’ve found QFF. Management is much more effective if you take action together.
- We love a good food swap but think carefully before transporting or sharing fresh produce (or seedlings potted in soil) if there is a risk of spreading this pest.
Which plants are susceptible to QFF?
QFF lay eggs in fruits and ‘vegetables’ that are technically fruits. Plants that are highly susceptible tend to have a thin skin and include apples, pears, loquats, quinces, plums, apricots, nectarines, cherries, peaches, feijoas, cherry guavas, tomatoes and capsicum. Many gardeners report that cherry tomatoes are more resistant to QFF than larger varieties.
Fruit fly will infest other fruits like mulberries, figs, grapes, blueberries, olives and persimmon if preferred hosts are not available, and have also been found in the native kangaroo apple.
There appear to be very few fruiting plants that are never affected by QFF, but plants that are less likely to be targeted tend to have thicker skins like pomegranates, citrus fruit with thick skins (not Meyer lemon), kiwis, passionfruit and avocados with thick skins (not Bacon, Fuerte or Rincon).
Queensland Fruit fly is a new pest for our region and we are all learning together about how it behaves this far south. Please let us know if you have discovered fruit fly in other crops so we can keep this advice up to date.
How do I manage QFF?
We’ll need to learn to live with QFF, but there are steps we can take to manage this pest.
- The most certain defence for home gardeners is fine netting designed for insect exclusion. This can be used to cover entire trees, or as bags around individual fruit. Fruit can be susceptible from an early stage, so for guaranteed protection nets need to go on as soon as possible after the flowers have been pollinated, when the fruit first starts to grow. QFF can lay eggs through netting if it is touching the fruit, so check carefully for clearance.
- Male QFF traps (using a pheromone) are commercially available and can be used to monitor for the presence of this pest, but are not considered a management technique.
- Female QFF traps or bait (a protein and sugar bait with poison) are commercially available. A certified organic fruit fly bait is available and recommended for home gardeners. Bait painted onto trees must be reapplied after rain.
- Homemade traps (a protein and sugar bait with no poison) can be made using a recycled plastic container with 1 tsp vegemite, 1 tsp sugar and some fruit peel, mixed with a few cups of water. Poke a hole 2/3rds up the container and hang in a shaded spot, 2m apart in susceptible trees. Refresh bait weekly for best results.
How can I design my garden to be less attractive to QFF?
The design of your garden can make a real difference. To create a food garden with more resilience you can:
- Consider how much effort you are willing to put in to QFF management. If you have limited time and energy, choose fewer susceptible fruiting plants and grow more vegetables and native plants.
- Choose dwarf fruit varieties and/or prune trees to keep them small so they are easy to inspect and net.
- Run chickens under susceptible fruit trees so they can clean up any fallen fruit and scratch for larvae and emerging adults to break the cycle.
- Create habitat for fruit fly predators such as small insect-eating birds, parasitic wasps, ants and spiders. See our habitat gardening resources for more info. (These will generally reduce pest pressure but are usually not enough to avoid damage from QFF.)
- Select fruiting varieties that miss the peak fruit fly period. Select fruits that ripen early in spring, or in late autumn/winter.