Queensland fruit fly or Qfly (Bactrocera tryoni) is one of the most damaging pests of fruit and vegetables in Australia. This insect is native to eastern Queensland and north-eastern New South Wales, but has extended its range due to transport of infected fruit, the planting of exotic host crops, and climate change.
Now that the pest has extended its range, Queensland fruit fly (QFF) can be found in Queensland, New South Wales, the Northern Territory, and Victoria. The states of Western Australia, South Australia and Tasmania are free of the pest, but the exotic Mediterranean fruit fly (medfly) is present in Western Australia. QFF outbreaks mainly occur from November to May, but some pest activity may continue during the cooler months.
What makes this pest particularly destructive is that it attacks almost every fruit and fruiting vegetable, causing the fruit to rot on the inside and drop to the ground, making every part of the fallen fruit inedible. When pest numbers are high they can almost destroy a whole crop. Furthermore, this pest will not only attack fruit when its growing and ripening, but also after it has been harvested if it is unprotected.
Identifying Queensland Fruit Fly
There are many different types of fruit flies native to Australia, and most are not agricultural or garden pests. There are also introduced exotic fruit flies in Australia which aren’t native and are pests. There are also lots of other little flies that may only be a nuisance but are sometimes mistaken for fruit flies.
Correct identification of a pest is critical before attempting to devise a solution!
Queensland fruit fly or Qfly (Bactrocera tryoni)
- Approximately 6-8mm long.
- The head has red eyes and two very short antennae which are barely visible.
- The thorax (middle section between head and abdomen) is reddish-brown with and distinct yellow patches on the sides and back.
- The abdomen (rear section of the body) is solid dark brown in colour, while the legs are a lighter shade of brown.
- The wings are clear with no markings.
Mediterranean fruit fly or Medfly (Ceratitis capitata)
- Much smaller at 3-5mm long.
- The head also has red eyes and two very short antennae which are barely visible.
- The thorax (middle section between head and abdomen) has an irregular mosaic of black and silver patches.
- The abdomen (rear section of the body) has two light-coloured rings circling around it.
- The wings are not clear, but mottled with distinct brown bands extending to the wing tips.
All fruit flies hold their wings outstretched in a horizontal position when walking, and flick them in a characteristic manner.
The little flies that fly up into the air when the compost bin lid is lifted or fly around fallen rotting fruit are Vinegar Flies, they are harmless and are NOT fruit flies.
The annoying little flies that proliferate around indoor plants and fly around people’s faces indoors, and multiply inside the house if food waste is left in in uncovered bins (especially in offices when people dump apple cores and banana peel in their desk waste paper basket!) are Fungus Gnats, they also are NOT fruit flies.
Which Crops Does Queensland Fruit Fly (QFF) Attack?
Tomato infected by Queensland fruit fly, note the rotted inside of the fruit and the maggot which has jumped out onto hand in the upper right hand corner of the photo! (Image credit – contributed by Sarah Hardgrove, Wildgrove Horticulture)
Abiu, Acerola, Achachairu, Apple, Apricot, Avocado, Babaco, Banana, Black sapote, Blackberry, Blueberry, Boysenberry, Brazil Cherry, Breadfruit, Caimito (Star apple), Cape gooseberry, Capsicum, Carambola (Star fruit), Cashew apple, Casimiroa (White sapote), Cherimoya, Cherries, Chillies, Citron, Cocoa berry, Cumquat, Custard apple, Dates (fresh), Durian, Eggplant, Feijoa, Fig, Goji berry (fresh), Granadilla, Grapefruit, Grapes, Grumichama, Guava, Hog plum (Vai-apple), Jaboticaba, Jackfruit, Jew plum, Ju jube, Kiwi fruit, Lemon, Lime, Loganberry, Longan, Loquat, Lychee, Mandarin, Mango, Mangosteen, Medlar, Miraclefruit, Mulberry, Nashi, Nectarines, Olives, Orange, Passionfruit, Pawpaw, Peacharine, Peach, Pear, Pepino, Persimmon, Plumcot, Plum, Pomegranate, Prickly Pear, Pummelo, Quince, Rambutan, Raspberry, Rollinia, Rose Apple, Santol, Sapodilla, Shaddock, Soursop, Sweet apple (Sweetsop), Star apple, Star fruit (Carambola), Strawberry, Tamarillo, Tangelo, Tomato, Vai Apple (Hog plum), Wax Jambu (Rose apple), White Sapote (Casimiroa)
This is almost every fruit except for the ones listed below!
Note: Mediterranean fruit fly (medfly), which is present in Western Australia, attacks a narrower range of crops than QFF.
Which Crops Are NOT Attacked by Queensland Fruit Fly (QFF)?
Choko, Coffee berry, Dates (dried), Dragonfruit, Monstera, Pineapple
Note: non-fruiting crops such as leafy green vegetables, grains, brassicas and root crop plants are not affected by QFF.
Queensland Fruit Fly (QFF) Life Cycle
The life cycle of QFF from egg to adult is 5 weeks in hot weather, allowing multiple generation of the pest to breed during the warmer seasons. The female only needs to mate only once to produce several hundred eggs in her lifetime, and can lay up to 100 eggs a day.
There are four stages in the Queensland Fruit Fly (QFF) life cycle:
- Egg – The female uses her ovipositor to sting ripening or ripe fruit, laying 6-12 eggs beneath the skin of the fruit. The eggs are white, banana-shaped and 1mm long. Since the eggs are inside the fruit, thy aren’t visible, but the site where the fruit has been stung will show a small puncture mark with oozing sap, or may visible as a dimple or indentation on the surface of the fruit sized like the top of a pin. On tomatoes, the sting location will remain as a green spot as the tomato ripens and changes colour.
Queensland fruit fly eggs laid beneath skin of fruit (Image credit – source image from NSW Department of Primary Industries, modified and edited by Deep Green Permaculture)
- Larva (Maggot) – The eggs hatch after 2-4 days, and a small creamy yellow larva (maggot) emerges from each egg. The maggots are carrot-shaped, with dark mouth hooks (cutting jaws) at the narrow pointed end where their head is. They tend to eat towards the centre of the fruit, and they carry bacteria which cases the fruit to rot and drop to the ground, making the fruit completely inedible. The maggots grow to around 8-11mm long when mature and are a pale yellow colour. These maggots also can jump! They sometimes curl into an upside-down U-shape and straighten quickly to launch themselves when exposed from their protection inside a fruit. Maggot-Infested fruit may appear in good condition from the outside, but the damage is visible when fruit is cut open. After 2-6 weeks, when the maggot has finished growing, which is usually when the fruit has fallen to the ground, it will cheat its way out of the fruit and burrows into the soil.
Queensland fruit fly larvae (maggots inside) a peach, showing interior rotting of fruit (Image credit – source image from NSW Department of Primary Industries, modified and edited by Deep Green Permaculture)
- Pupa – Once the maggot has burrowed into the soil, it will pupate – it transforms into a hard oval or barrel-shaped, brown-coloured pupa which is around 4-5mm long. The adult QFF gradually develops inside this protective pupal case over a period of 2-6 weeks. Note: QFF larvae will also pupate in compost bins if infected fruit is thrown in there!
Queensland fruit fly pupae are around 4-5mm long and brown in colour (Image credit – source image from NSW Department of Primary Industries, modified and edited by Deep Green Permaculture)
- Adult – After adult QFF have developed inside their pupa, they leave their protective underground shelters and emerge from the ground. The adults live for many weeks and therefore need to feed. They require sugars for energy, which they source from flower nectar, just like beneficial insects, and from honeydew exuded by sap-sucking pest insects such as aphids and whitefly. The female QFF need protein before they can become sexually mature to mate, and they source protein from bacteria on leaves (which grow well during warm, humid conditions), animal droppings and juices in fruits. After feeding and mating, females search for ripe fruit to lay their eggs inside, restarting the cycle.
Queensland fruit fly adults are around 6-8mm long, comparison to a match head (Image credit – source image from NSW Department of Primary Industries, modified and edited by Deep Green Permaculture)
Adult Queensland fruit fly on raspberry (Image credit – source image from NSW Department of Primary Industries, modified and edited by Deep Green Permaculture)
Queensland fruit flies can either overwinter as pupae underground, or as adults in sheltered locations, they do survive winters, and become active when the weather warms up, especially after periods of rain or high humidity.
The following image produced by the Government of Tasmania shows the QFF life cycle graphically, you can click on the image to enlarge:
The Best Ways to Control Queensland Fruit Fly
Is any one method of pest control 100% successful? It’s been long known that none are, but that doesn’t mean that they can’t be used effectively. The strategic pest management solution that is employed worldwide is to combine various pest solutions to increase effectiveness, this approach is known as Integrated Pest Management, or IPM for short.
Listed below are various types of controls that can be combined in whatever way to achieve optimum pest control outcomes:
These controls are practices which disrupt the environment of the pest, reducing pest establishment, reproduction, dispersal, and survival.
1. Clean up any fallen fruit as a matter of good garden hygiene, .
2. Destroy infected fruit by either of the following methods:
- immerse infected fruit in water for several days, making sure it’s submerged and not floating on the surface
- Solarize infected fruit by placing it in a black plastic bag, tie it shut and leave in the sun to heat up and kill pests.
These controls block pests out, make the environment unsuitable for them, or kill them directly, such as barriers and traps.
1. Exclusion netting is designed to keep insects out, it’s made of a very fine mesh of around 2mm, and it comes in many forms, as drawstring bags which can be used to bag fruit while still on a tree, drawstring sleeves with two open ends which can cover whole branches, and formed tree covers which can be placed over entire trees if they’re kept to a reasonable size.
This fine netting also keeps out a range of pests, such as birds and possums (rats and mice chew through netting of all kinds) and provides 20% shade which stops fruit burning.
Using fine mesh insect netting is a cost effective solution as it’s cheap, more durable than more open weave netting, and can be used year after year.
Insect exclusion netting can also be purchased at any length from a roll, and comes in various widths broad enough to cover almost anything from vegetable beds to espalier trees and berries on fences and trellises.
When using insect exclusion netting, make sure it is not resting against the fruit otherwise the fruit flies can reach the fruit and sting them fruit surface.
The key to netting fruit trees is to keep them small, either by using dwarf trees or summer pruning full-sized trees to keep them to a manageable size. Stone fruit are particularly susceptible to QFF, this pest has a preference for soft fruit with a thin skin. If you must grow stone fruit, keep them pruned small, and apricots must be pruned in summer anyway, as they get the gummosis disease where they ooze sap if they’re pruned in cold, wet weather.
To manage fruit fly in fruit trees with netting, prune trees to keep them small, the accepted rule is quite simple and straightforward – If you can’t reach it, cut it off!
2. Traps are designed to capture pests, either for monitoring purposes or eradication.
The traps exploit the pest’s requirement for sugars and protein, and will capture both male and female QFF.
An example of this type of trap is the Cera Trap which is hung in a fruit tree to lure and drown fruit flies. The bait liquid can be purchased separately to refill the trap when the liquid evaporates (after around 3-4 months).
How is this traps used? I’ve copied the manufacturer’s instructions below:
Description: The effective and environmentally appropriate solution to the problem of Mediterranean Fruit Fly (Ceratitis capitata) and Queensland Fruit Fly (Bactrocera tryoni). Targets both male and female fruit fly. Use Cera Trap before fruit flies start attacking the fruit. Cera Trap should be hung in trees when the fruit are small and still developing. Ideally, hang the traps when fruit reaches approximately one third its final size. The traps should be hung on the northern side of the tree, at a height of approximately 1.5 metres and within the tree canopy.
How to use: The traps should be placed evenly throughout the garden, except where there are recognised areas of high insect activity, these areas should be reinforced with additional traps. To reduce pest numbers it is essential to install the traps at least 45 days prior to fruit ripening.
Ingredients: Hydrolized protein
These control agents are natural enemies of the pest, and can be used to keep their populations in check.
There are several predators of QFF, but they only reduce the numbers slightly, and they prey on the pest at its various life cycle stages:
- QFF eggs – predators are wasps
- QFF larvae (maggots) – predators are ants, ground beetles
- QFF adults – predators are spiders, dragonflies, robber flies, and birds such as swallows, willy wagtails and restless flycatchers
Running poultry under fruit orchards is another way of cleaning up QFF, as chickens will consume any fallen fruit and any pest insects they find.
Chemical control is defined as the use of pesticides to control pests. In IPM, chemical controls are used only when needed, and usually as a last resort, combined with other methods for more effective, long-term control.
One of the safest chemical controls for QFF are pheromone traps which attract male Queensland fruit fly to a poisoned bait, killing them and breaking the breeding cycle.
An example of such a trap is the Eco-lure, which uses a replaceable wick containing the pheromone along with the organophosphorus insecticide Maldison (Malathion). This insecticide is quite toxic when sprayed on plants, but when confined to a wick inside a trap, it’s environmental impact is low as it presents no treat to anything other than male QFF, so it’s an environmentally friendly solution.
How is this traps used? I’ve copied the manufacturer’s instructions below:
Description: eco-lure male Queensland fruit fly trap is an excellent tool for monitoring fruit fly presence in your garden. It contains a wick which has been impregnated with a pheromone attractant and a non-organic insecticide. Male QLD fruit flies are attracted to the pheromone, enter the trap and are killed when they touch the wick.
How to use: Hang in foliage at the beginning of the season and check regularly. When dead flies appear you’ll know flies are active and it is time to start spraying eco-naturalure to control females as well. eco-lure on it’s own is not sufficient to completely protect fruit which is why we recommend including eco-naturalure as part of your protection program. Replace wicks every 3 months or as required.
Powerful pheromone attractant is irresistible to male QLD fruit flies
Attracts and kills male QLD fruit flies
Targets only male QLD fruit fly and won’t attract beneficial insects
eco-lure trap will attract flies from approximately 400m
Not for WA as the pheromone is not attractive to Mediterranean fruit flies (Medflies).
Another form of chemical control bait uses a mixture of sugar and protein to attract both male and female QFF and an insecticide to kill them when the bait is eaten. These baits are sprayed onto small areas of plant foliage, not over the whole tree or fruit.
An example of such a spray bait insecticide Eco-naturalure or Yates Nature’s Way Fruit Fly Control, which combines the sugar and protein bait which attracts QFF with the insecticide Spinosad, an aerobic fermentation product or metabolite of the soil bacterium, Saccharopolyspora spinosa. This insecticide is moderately toxic to earthworms and very highly toxic to bees but it is claimed that the evidence suggests that spinosad has little or no effect on honey bees and other beneficial insects after sprays have dried.
How is this product used? I’ve copied the manufacturer’s instructions for Eco-naturalure below:
Description: Registered Organic fruit fly bait spray for both male and female flies. Controls Queensland and Mediterranean fruit flies and has no withholding period. It combines specific food-based attractants which target only fruit flies and a bacteria-derived insecticide called spinosad. Fruit flies eat the bait and are killed by the organic insecticide.
How to use: eco-naturalure is applied as a spot spray in 30cm patches around the foliage of plants. No need to cover the whole tree or all the fruit. Must be applied weekly and after rain.
It is very important to start protecting fruit early in the season. The aim is to kill the fruit flies before they sting the fruit and to prevent population numbers exploding later in the season. We recommend applying eco-naturalure from petal drop as flies have been shown to sting green fruit as small as a marble.
(Author’s note: This product can be applied to foliage, branch or tree trunk or to a plywood board)
Effective on Queensland and Mediterranean fruit flies
Attracts and kills male and female fruit flies
Only requires spot spraying (entire plants and fruit do not need to be sprayed)
Targets only fruit fly and won’t harm beneficial insects
No withholding period (even if you get some on the fruit)
Registered Organic (Australian Organic)
For people fighting the QLD fruit fly (found in all the mainland eastern states) we strongly recommend you also hang an eco-lure trap. This is a very useful monitoring tool to let you know when fruit flies are active and when to start spraying. Unfortunately the eco-lure trap does not work on the Mediterranean fruit fly found in WA.
A really safe way to use spray bait insecticides such as this for QFF is to spray them onto a 30cm x 30cm plywood board, and then cover the board with a mesh large enough to let fruit flies through but small enough to prevent bees getting through. Rather than applying weekly after rain, construct a shelter to house the board and prevent the bait washing off in the rain and getting into the soil where it can affect earthworms!
The most effective solution to Queensland fruit fly is an integrated pest management solution, where orchard hygiene and destruction of infected fruit, netting, trapping and the use of spray baits are combined to maximise pest control effectiveness.
Why Queensland fruit fly has moved south in Australia
When dealing with a pest problem, it’s always valuable understanding why the problem has come about. In the start of this article I mentioned that the QFF pest has extended its range due to transport of infected fruit, the planting of exotic host crops, and climate change, which is worth expanding on.
The shift due to climate change is a significant contributing factor in the spread of the pest. According to the NSW Government Department of Primary Industries publication “The effect of climate change on the geographical distribution of Queensland fruit fly in Australia” by Bernie Dominiak and Marja Simpson, in general, there has been a increase in summer rainfall and decrease in winter rainfall across Australia, as shown in the AEGIC diagrams below. The authors state that “Projections for increasing summer rainfall and warmer winter temperatures for southern Australia will be of benefit to Qfly establishment”.
In the diagrams below from the Australian Export Grains Innovation Centre (AEGIC), we can see that when we compare rainfall data from the period 1900-1999 against the period of 2000-2015, there is a clear southward movement of warmer season rainfall.
With increasing summer rainfall and warmer winter temperatures in southern Australia, the pest is forecast to spread further south, increasing in range and abundance, making Queensland fruit fly a more commonplace pest which gardeners in the temperate states will have to deal with more and more.