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Queensland Fruit Fly (QFF)

Alert and advice for Melbourne gardeners – January 2021

Have you found maggots in your produce? Gardeners from across Melbourne are now reporting the presence of Queensland Fruit Fly (QFF). These devastating horticultural pests attack a wide range of common fruit and vegetables including apples, pears, stone fruit, feijoas and tomatoes. We encourage all home gardeners to learn to identify and respond to this pest.

How to recognise Queensland Fruit Fly

Queensland Fruit Fly

Queensland fruit fly adult. Actual size is 5-10mm. (Image by Agriculture Victoria)

An adult QFF is 5-10mm, with a yellow band. (NB: Small flies hovering around a compost bin or fruit bowl are sometimes described as ‘fruit flies’ but are not Queensland Fruit Fly).

Eggs are difficult to see, but fruit infected with QFF eggs can develop small dimples. Eggs are laid in unripe fruit.

Infested fruit
Fruit Fly Larvae

Queensland fruit fly larvae maggots (Image by Agriculture Victoria)

Larvae (maggots) develop inside the fruit which are a cream-white colour and grow to 10mm. 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.

I’ve found QFF in my garden. What should I do now?

If you’ve found QFF in your garden, there are some important steps you can 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 especially  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.
  • Pasteurise by heating (in plastic bag in sun for a week, or boiling) or freezing affected produce before disposal. Do not put untreated produce in compost or waste bins as this will facilitate further spread.
  • Let your neighbours know that you’ve found QFF. Control methods are much more effective if you take action together.
  • Swapping and sharing produce is one of the joys of gardening, 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?

Plants that are highly susceptible are: apples, pears, loquats, quinces, plums, apricots, nectarines, cherries, peaches, feijoas, cherry guavas, tomatoes and capsicum.

Fruit fly may infest other fruits like mulberries, grapes, blueberries and persimmon if preferred hosts are not found.

Plants that are reportedly not susceptible are: pomegranates, citrus fruit with thick skins (not Meyer lemon), kiwis, passionfruit and avocados with thick skins (not Bacon, Fuerte or Rincon).

Fruit fly is a new pest in Melbourne 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?

Unfortunately we’ll need to learn to live with QFF, but there are steps we can take to manage this pest.

  • Fine netting designed for insect exclusion can be used to cover entire trees, or as bags around individual fruit. Fruit is susceptible from an early stage, so 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 an effective management technique.
  • Female QFF traps and/or bait (a protein and sugar bait with poison) are commercially available and can be part of an effective management plan. A certified organic fruit fly bait is available and recommended for home gardeners.
  • 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.

The design of your garden can make a significant difference to QFF management. To create a food garden with more resilience you can:

  • Consider how much effort you are willing to put in to fruit fly management. If you have limited time and energy, choose more plants from the list that are less or not susceptible.
  • Choose dwarf varieties or prune susceptible fruit trees to keep them small so they are easy to net. Most larger trees can be progressively pruned by about a third a year to reduce height without shocking the tree.
  • Run chickens under susceptible fruit trees so they can clean up any fallen fruit and scratch for larvae and pupae in the soil to break the cycle.
  • Create habitat for fruit fly predators such as insect-eating birds, parasitic wasps, ants and spiders.
  • Select early fruiting varieties that may miss the peak fruit fly period during the warmer months.

Check out this excellent article on fruit fly control methods suitable for organic gardens and the Bye Bye Fruit Fly segment on Gardening Australia. See also Agriculture Victoria and the National Fruit Fly website.