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 fly 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?
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:
Stage 1. 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, they 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.
Stage 2. 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 can jump! They 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 chew its way out of the fruit and burrow 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)
Stage 3. 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!
Stage 4. 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 also 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 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.
Beyond being just a physical barrier, research has shown that reflected white light had a repellent effect on Queensland fruit fly, and since all white objects reflect white light, so Queensland fruit fly are repelled by white objects, including white netting.
Testing showed that the product Vent Net, a white, open strand knitted fabric netting with a mesh size of 6mm x 4mm, which the flies quite easily can fit through, still acted as an effective visual barrier. This netting is used for screening the sides of greenhouses and other structures, to keep out birds and large insects, and to reduce the impact of wind or strong rain. The white colour alone served as a deterrent.
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’s essential to install the traps at least 45 days prior to fruit ripening.
Ingredients: Hydrolized protein
Another type of trap is the male pheromone trap such as the Ryset Fruit Fly Trap which uses a synthetic pheromone lure such as the Wild Wild May Fruit Fly Attractant to lure male Queensland fruit fly into the trap where they drown, killing them and breaking the breeding cycle.
Ryset Fruit Fly Trap and Wild May Fruit Fly Attractant
How is this trap used? I’ve copied the manufacturer’s instructions below:
Ryset Fruit Fly Trap
- Fill to a depth of 30mm with suitable liquid bait such as WILD MAY.
- Reseal and hang in the middle of the tree.
- The fly will enter the trap, enticed by the bait, but will be unable to escape, where it will drown in the liquid.
- Top up the bait as required.
Wild May Fruit Fly Attractant
ACTIVE CONSTITUENT: maximum 0.5 g/L 4-(p-hydroxyphenyl)-2-butanone and minimum 0.25 g/L 4-(p-hydroxyphenyl)-2-butanone acetate
Pesticide Free Lure for attracting and killing the male Queensland Fruit Fly (Bacterocera tryoni)
DIRECTIONS FOR USE:
- Pour attractant into base of trap supplied to a minimum depth of 20mm.
- Place trap upwind in shaded branch on the eastern side of the tree approximately 1.2 metres off the ground.
- Place four traps per hectare equally spaced around areas where fruit flies are to be monitored/controlled.
- Recharge traps when liquid attractant evaporates to a depth of 15mm.
- When recharging the traps, it is advisable to remove dead flies from the trap liquid by an effective means such as pouring the liquid through a sieve or using a small spoon.
3. Barrier Sprays create a coating on the fruit which deters pests from laying their eggs there.
An example of this type of barrier spray is calcined kaolin, which is sold as Surround WP in the agricultural sector, and under various other names in the consumer gardening industry.
Calcined kaolin is a form of clay, and is certified for use in organic gardening. It forms a white film over stems, leaves and fruit, reflecting the sun’s rays to prevent fruit sunburn, which is its traditional agricultural use.
It also acts as a barrier to pests, and has been used for this purpose by European organic farmers for quite a while now. The layer of calcined kaolin makes it hard for insects to walk on and presents an unnatural surface for them to interact with, causing irritation, confusion and an obstacle to feeding and egg-laying. It may also create a barrier which prevents fungal spores establishing on leaves.
Immature apples sprayed with calcined kaolin which forms a protective barrier against pests
This spray is effective against gall wasp, codling moth and oriental fruit moth, leafhoppers, powdery mildew, stink bugs and thrips. Field trials in Bundaberg Qld and Silverdale in NSW have shown that calcined kaolin is also effective against Queensland fruit fly. The only qualifiers mentioned in the Horticulture Innovation Australia publication “Final Report New in-field treatment solutions to control Fruit Fly (2), Jenny Ekman, Project Number: VG13042” was as follows:
“Kaolin treated plants were next to non-treated ones –flies may try harder to find host fruit if they do not have an alternative so readily available. Whether postharvest washing and brushing can remove the material is a key concern. White residue on vegetables will not be acceptable to customers. Cost may also be an issue, as Surround® is relatively expensive, and quite a large amount needs to be applied to get good coverage.”
Put simply, the Queensland fruit flies possibly may have avoided the sprayed fruit because they had access to unsprayed fruit nearby which was more attractive, this would need to be tested further. The second concern was that farm growers would find it harder to sell the unwashed vegetables, which is not of any concern to home gardeners.
As mentioned earlier, white objects have a repellent effect on Queensland fruit fly, as they are quite unnatural in appearance to them, and when fruit is sprayed with calcined kaolin, the white colour makes it less desirable to them.
How is calcined kaolin spray used?
Calcined kaolin is sprayed on leaves, stems and fruit – avoid spraying on flowers, as they don’t function to well with a layer of clay over them!
- 2.5‐5 kg of calcined kaolin to 100 L of water, or
- 25-50g of calcined kaolin to 1 L of water
Spray at all angles to get nice, even coverage all over the fruit, spraying to point of run off, or ‘near drip’.
Only two applications are required each year.
- For the first application, use 50g (or 200ml) of calcined kaolin to 1 L of water, spray early spring when the fruit start forming. QFF have been shown to sting green fruit as small as a marble
- The second application is made to maintain coverage, so a half-strength spray of 25g (or 100 ml) of calcined kaolin to 1 L of water can be used, to cover the fruit as it grows.
Calcined kaolin does not wash off very easily, even under heavy rain, but if needed, spraying can be repeat monthly using half-strength just like the second spray.
Note: Combining calcined kaolin with netting increases effectiveness of both controls, and reduces the amount of calcined kaolin washing off.
Many people don’t have a way of weighing the calcined kaolin powder when mixing it, so I’ve worked out the conversion of weight to volume for gardeners to make things easier:
- Calcined Kaolin: 25g = 100ml into 0.5 L of water, or
- Calcined Kaolin: 50g = 200ml into 1 L of water
Only mix as much as you need, as calcined kaolin can’t be stored once it’s mixed.
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, its 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 trap 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 its 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.
Timing Queensland Fruit Fly Controls Through the Year
To effectively control QFF, appropriate pest control measures need to be deployed at the correct times of year to coincide with the various life cycle stages of the pest.
Controls to Put into Place in Spring
During this time adult QFF emerge from the soil when weather warms up, and females search for sources of protein to feed on before they can become sexually mature to mate.
- Hang Queensland fruit fly pheromone traps (such as the Eco-lure trap or Ryset Fruit Fly Trap) in foliage at the beginning of the season to trap male Queensland fruit flies and check regularly. The Eco-lure traps are effective for three months, and can take a replacement wick, while the Ryset traps just need to be topped up with Wild Mays attractant.
- When dead male Queensland fruit flies appear in the pheromone traps, you’ll know they’re active and starting to mate, and this is the time to apply a sugar-protein spinosad insecticide (such as Eco-naturalure or Nature’s Way Fruit Fly Control) to control females as well. Apply these insecticides 5 weeks before ripening – the recommend time is as early as petal drop, as QFF have been shown to sting green fruit as small as a marble. Must be applied weekly and after rain.
- Use sugar-protein liquid bait traps (such as Cera Trap) before fruit flies start attacking the fruit, when the fruit are small and still developing. Ideally, hang the traps when fruit reaches approximately one third its final size. To reduce pest numbers, it is essential to install the traps at least 45 days prior to fruit ripening. Refill the trap when the liquid evaporates, which is after around 3-4 months.
- Net trees and berries with insect exclusion netting or fruit bunches with insect exclusion netting bags when the fruit first starts forming. Once pollination has occurred, all insects can be excluded to protect the fruit. Summer prune new growth back by half to make netting easier.
Important note: It is not possible to control Queensland fruit fly by using the male fly pheromone traps on their own. The method known as the Male Annihilation Technique (MAT) works by luring and killing male flies to preventing female flies from mating. Even if 99% of the male flies are killed, it only takes one surviving male fly to mate with the remaining females, as the male flies can mate repeatedly! This is why it’s important to use controls that target both male and female Queensland fruit flies.
Controls to Put into Place in Summer
During this time fruit are naturally ripening and falling to the ground. Fruit infected with QFF will also fall to the ground, the larvae when mature will leave the fruit and burrow into the soil.
- Run poultry, such as chickens or other birds under fruit tree orchards to consume any fallen fruit and any pest insects they find.
- Collect fallen fruit, and destroy infected fruit by solarising or immersion.
Controls to Put into Place in Autumn and Winter
During this time QFF fly pupa are dormant in the soil, emerging as adults in spring when the weather warms up.
- Run chickens under fruit orchards to scratch and dig into the soil to clean up dormant QFF pupating in the soil.
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.