Detect and Respond

We respond to fruit fly detections and outbreaks to protect South Australia.

Fruit fly detection and reporting methods

From time to time, isolated fruit flies are detected in the South Australian trapping grid. These individual detections do not constitute a fruit fly outbreak which is only triggered if a threshold number of fruit flies are detected or if fruit fly larvae are found in locally grown fruit or fruiting vegetables.

If an outbreak is declared, early detection means the flies can be eradicated quickly.

Fruit flies can be detected from:

When is a fruit fly outbreak declared?

A Queensland fruit fly (Q-fly) outbreak is declared when any of the following occurs:

  • 5 male or non-pregnant female flies are trapped within 1 km within a rolling 2 week period
  • 1 pregnant female is detected
  • 1 or more larva are detected in locally grown fruit.

A Mediterranean fruit fly (Med-fly) outbreak is declared when any of the following occurs:

  • 3 male or non-pregnant female flies are trapped within 1 km within a rolling 2 week period
  • 1 pregnant female is detected
  • 1 or more larvae are detected in locally grown fruit.

What happens once an outbreak is declared?

If an outbreak is declared, the area around the fruit fly discovery point is split into quarantine areas.

For Queensland fruit fly this is:

  • an Outbreak Area (1.5km radius around the discovery point)

We ensure that no fruit or vegetables that host fruit fly (except when cooked or preserved) are removed from the outbreak area.

  • a Suspension Area (15km radius around the discovery point).

All susceptible host fruit must be treated before removal from the suspension area.

For Mediterranean fruit fly this is:

  • an Outbreak Area (1.5km radius around the discovery point)

We ensure that no fruit or vegetables that host fruit fly (except when cooked or preserved) are removed from the outbreak area.

  • a Suspension Area (7.5km radius around the discovery point).

All susceptible host fruit must be treated before removal from the suspension area.

In the event of an outbreak we also:

  • destroy all fruit on infested trees in the eradication area
  • undertake bait spotting
  • release sterile fruit flies
  • continue to apply bait spotting for at least 2 weeks.

Bait spotting to attract and kill fruit flies

Baiting involves applying an organic bait to suitable foliage in both front and back yards.

This includes:

  • Applying the bait as a 40ml dose to vegetation with around 150 spots applied per hectare (this equates to around 12 bait spots per property)
  • Re-applying the organic bait regularly until we are confident the adult fruit flies have been controlled
  • If your property is within 200 metres of a detection site, the bait will be applied twice a week; all other parts of the outbreak area will have bait applied once a week.

Baiting typically takes six to eight weeks, depending on the number of detections made. After this time, bait application stops and sterile flies may be released in the area.

The bait is most effective when applied to the backyard of properties within the outbreak area, as this is most often where host fruit trees are located. If this isn’t possible, bait will be applied to other suitable foliage within your property.

Treatment and disposal of susceptible host fruit and vegetables

We visit properties within 1.5km of the outbreak centre and remove, treat and dispose of fallen susceptible host fruit and vegetables, also known as hygiene work.

Hygiene involves collecting fallen fruit from backyards across the outbreak area. At a detection site where fruit fly maggots are found, all fruit from trees will be collected. Once an outbreak is declared, staff will assess properties within the quarantine area as soon as possible. If you have fruit trees in your backyard, our hygiene team will visit your property once a week during the eradication program.

When and why we use sterile male fruit flies

A sterile fruit fly release is sometimes used once baiting and hygiene work is complete.

For this to be effective, baiting must reduce the number of wild flies present in the outbreak area.

Six to eight weeks after bait spotting is complete we release 1,000,000 sterile flies per square kilometre, if required. We do this once or twice a week for up to 12 weeks.

  • Sterile flies are usually released from a calibrated ground unit on the back of a vehicle which slowly drives around the outbreak area.
  • The sterile flies mate with wild females who then lay infertile eggs. This prevents the fruit flies from breeding and spreading.
  • This part of the eradication program can take up to 12 weeks and there is no need to access backyards.

The combination of bait spotting and sterile insect technology are currently the world’s best practice for the eradication of fruit flies.

Some of the sterile flies are produced at the Sterile Insect Facility in Port Augusta.

Important information for residents in outbreak areas

You can help with the response program in the following ways:

Do

  • Provide easy access to your front and back gardens so Biosecurity SA staff can complete their work quickly
  • Report any maggots found in fruit or fruiting vegetables immediately. Place in a plastic bag and contact the Fruit Fly Hotline (1300 666 010) to arrange collection.
  • Collect fallen/over-ripe fruit and fruiting vegetables, seal them and place in your green bin.

Do not

  • Leave home grown fruit and fruiting vegetables lying on the ground.
  • Compost any fruit or fruiting vegetables, including those bought from a shop during the quarantine period.

You must not remove home grown fruit, fruiting vegetables or garden waste from your property. This also includes NOT putting this fruit into lunch boxes for work or school if consumption is going to occur outside the quarantine area.

Please place unwanted fruit and vegetable waste in green bins as usual, as a system is in place for the green waste during fruit fly outbreaks such as this.

You can cook or preserve excess home grown fruit and fruiting vegetables and such items are allowed to be removed from the quarantine area.

The length of a quarantine period varies between outbreaks as it is determined by the number of flies detected during a specified time period which is set under the National Code of Practice.

We realise the quarantine restrictions and eradication program will cause some inconvenience but your co-operation will assist greatly in helping to keep South Australia fruit fly free.

At the completion of an eradication program you will be advised by leaflet. Only after this can home grown fruit and vegetables be removed from your property.

Page Last Reviewed: 20 Feb 2020
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