Managing Queensland fruit fly in your home garden
Queensland fruit fly in Victoria
Queensland fruit fly (QFF) (Bactrocera tryoni) attacks a wide range of fruits and fruiting vegetables, leaving them inedible.
Produce damaged by QFF can cause real disappointment for home gardeners. If left uncontrolled, QFF can lead to total crop losses.
Managing QFF in your garden can be a challenge; however as with all pests, there are various strategies you can implement to protect your home-grown produce.
This information outlines strategies you can use in your home garden to control QFF and protect produce from damage.
While QFF activity generally increases in spring as the weather gets warmer, it is not strictly tied to a particular season.
If sufficiently warm weather persists into autumn or winter, fruit flies can continue through their life cycle providing that a suitable host fruit or fruiting vegetable is available.
Since host fruits mature at different times of the year, it can be useful to relate QFF activity to the host plant's growth stage (as shown below) rather than to the season.
As with all pest management, it's important to correctly identify the pest you need to treat (in this case, QFF) to ensure the control strategies you plan to implement are appropriate.
Adult flies are about seven millimetres long and are reddish-brown in colour, with distinct yellow markings. Many people confuse vinegar flies (which are known as fruit flies in some parts of the world) with QFF. Vinegar flies are much smaller insects and will not damage home-grown produce.
Most people discover fruit fly when they cut open their fruit and find it infested with creamy-white maggots (5 - 10 millimetres long) burrowing inside.
Other indicators of QFF activity include fruit skins with small puncture marks (stings) from where the female fruit fly has laid her eggs and prematurely ripened fruits.
Popular home-grown produce
A combination of the following methods will be needed to manage QFF in the home garden.
As QFF activity is not strictly seasonal, the plant growth stage can be a useful guide as to when each method should be used.
Successful QFF management in a given area depends on a high level of participation among gardeners. Encourage your neighbours to manage their host plants properly to help achieve the best results.
The fruits of some host plants can be attacked by QFF earlier than others and some host fruits persist on the plant for longer than others. This means gardeners should monitor different types of host plants for QFF at different growth stages, as shown in the table below.
QFF adults can be monitored by trapping. To check for maggots, fruit will need to be cut open because infested fruit may appear in good condition from the outside.
Do not travel with fruit or vegetables!
The best way to prevent QFF from spreading is to not travel with QFF host fruits or fruiting vegetables, especially those grown in home gardens, which have a higher chance of being infested with larvae than store-bought produce.
Heavy fines apply if you are caught travelling with QFF host produce into the Greater Sunraysia Pest Free Area.
Restrictions also apply to carrying fruit fly host materials into some other states and territories - for more information, visit www.quarantinedomestic.gov.au
Exclusion is the use of physical barriers to stop female QFF from reaching your fruit and vegetables. Possible barriers include:
Nets: Many people construct home mosquito nets over PVC tubes and stakes to protect their fruit trees; some use outdoor gazebos as the zipper allows easy access to regularly inspect trees and harvest fruit as it ripens. Whatever you use, all nets must be either secured around the trunk base or to the ground. If you are unsure whether there are fruit fly pupae in the ground under your fruit trees, you should secure the bottom of the net to the trunk base. This will prevent any adult fruit flies emerging from the ground from infesting your new season crop.
Bags and sleeves: Place bags and sleeves over the fruit you want to keep. Remove any flowers or developing fruit from the plant that are not covered by a barrier. Secure bags and sleeves to the plant with tie wire, clothes pegs or string.
Nets, bags and sleeves are generally available from your local chemical or home garden retailer.
Pick and use any fruit as it ripens, don't leave it on the plant for fruit flies to attack. Collect and destroy any rotting or unwanted host fruit, whether it is on the ground or still on the plant.
Unwanted fruit can be microwaved to kill any maggots inside prior to being disposed of. Alternatively, place the fruit in a plastic bag, seal the bag and leave it in the sun for 5-7 days, or place it in a freezer for two days. The bagged fruit can then be discarded in your garbage bin. Do not add unwanted fruit to your compost or worm farm, or put it directly into your garbage.
Host plant removal and alternative plants
Remove any unwanted or unmanageable host plants from your property and replace them with non-host alternative plants.
Report neglected host plants on public land to the land manager (e.g. the local council), to encourage removal of the plants and improve QFF management across a wider area.
Cover spraying can be used to directly control adult QFF on contact, and destroy eggs and larvae within fruit. Cover sprays contain contact/systemic insecticides, and are sometimes mixed with a lure to help protect produce from initial fruit fly infestations. Cover sprays are generally applied to foliage and developing fruit.
Which QFF insecticides are available for home garden use? Home and community gardeners must only use registered insecticide products. All insecticides legally sold in Victoria are registered by the Australian Pesticides and Veterinary Medicines Authority and have passed rigorous testing to ensure they are safe and fit for their intended use.
Home garden products are usually available in small pack sizes or as ready-to-use formulations. Speak to your local chemical or home garden retailer about suitable products for your situation.
How do I apply QFF insecticides? Cover sprays can be harmful to human and environmental health if used incorrectly. Always read and follow the product label when using an insecticide. Usage directions can vary depending on the product and host produce you intend to spray. As the insecticide user, it is your responsibility to ensure the product is used according to the label directions.
Where can I get QFF insecticides? A range of insecticides that can be used to treat QFF are available from your local chemical or home garden retailer.
Can I pick fruit and vegetables I have sprayed? If you have sprayed your vegetables or fruit trees, you need to observe the withholding periods or 'DO NOT' statements on the product label. This will ensure that chemical residues have broken down to a safe and acceptable level. All fresh fruit or vegetables should be washed before consumption.
Trapping can be used to monitor and reduce QFF numbers.
Traps and attractants are designed to lure and kill fruit flies. They can be purchased from hardware, nursery and online suppliers. Place traps on host trees and other sites around the garden to draw fruit flies away from host produce.
You can also make your own traps using an empty soft-drink bottle (with lid). Please note that these traps may attract all insects - both pests and beneficials.
Cut three holes in the bottle about the size of a 10 cent piece, 10 centimetres from the top. Add the bait mixture: one cup of 100 per cent fruit juice (including pulp) and one tablespoon of cloudy ammonia (or wheelie bin cleaner) available from supermarkets and hardware stores. Tie a string around the neck of the bottle and hang it from the tree in the shade 1-1.5 metres from ground. The mixture can last up to three weeks but should be changed weekly for best effect.
Baits can be used to reduce QFF numbers in the garden. They consist of a protein attractant mixed with an insecticide and are usually spot-sprayed onto the trunks or foliage of host plants.
Adult flies are attracted to the bait droplets as a food source and killed by the insecticide.
You can purchase baits from hardware and nursery retailers.
Prune your fruit trees to a size which allows easy harvesting of fruit and easy application of netting, cover sprays or baits.
If possible, plant early-maturing fruit and vegetable varieties and/or harvest the produce early. This removes host material before QFF numbers have built up to damaging numbers.
Together with monitoring, these QFF management methods can be combined into strategies based on the stage of plant growth, to provide the most effective result.
|Management Strategy||Plant growth stage|
|Vegetative growth||Flowering||Fruit formation||Fruit maturity/harvest||End of growing season|
|Reduction of numbers|
Commonwealth Government's Advice for Home Gardeners in Australia website www.preventfruitfly.com.au