8 December 2015

Fruit flies are the world’s most common fruit pest.

They appear on almost every continent and millions of dollars are spent annually on their control and eradication. The damage they cause is widespread due to the extensive variety of fruit and vegetables on which they will lay their eggs – including  citrus, pome, stonefruit, tropical and temperate fruit and fruiting vegetables (for example capsicum and tomatoes). Many ornamental and native fruits are also attacked.

Two of the most economically damaging species of fruit fly in Australia are:

  • the native Queensland fruit fly (Q-fly, Bactrocera tryoni) in the eastern states and Northern Territory
  • the introduced Mediterranean fruit fly (Med-fly, Ceratitis capitata) in Western Australia.

The integrated pest management (IPM) strategy for fruit fly relies on a combination of traps, bait spotting and the release of sterile male flies. If IPM strategies are used by all producers in an affected production area it is also referred to as area wide management.

Traps placed throughout production areas are used to monitor the number and type of insects present. If fruit flies are detected, bait spotting is used for two weeks. A diluted mixture of both attractant and insecticide attract and then kill adult fruit flies. Spots of bait are placed where fruit flies might shelter, including trees, shrubs and ornamentals.

Alternatively, the bait can be diluted and sprayed on the crop directly, or some growers prefer to apply the bait around the perimeter of the growing area.

After bait spotting, sterile fruit flies are released into the area to reduce overall fruit fly numbers and to limit their reproduction. Since it’s the female fruit fly that damages fruit when laying eggs, the introduced sterile flies are male.  If a female fly mates with a sterile male, it will lay eggs that will not develop to adults, controlling or eliminating adult flies in the area.

The insects are sterilised using small doses of with radiation, which has the potential to weaken the flies making them less able to compete with the wild males for mating partners.

The success of area wide IPM for fruit flies depends on a number of factors and needs to be tailored to each crop or situation. The success of area wide IPM for fruit flies depends on a number of factors and needs to be tailored to each crop or situation.

In December 2013 the South Australian Government announced the funding of a new facility to breed sterile male Q-fly at Port Augusta. Sterile male Q-flies bred at the facility will be used to eradicate outbreaks interstate, as well as isolated detections in SA.

Sterile Med-fly have been used with success here and around the world, but this development will be a first for Q-fly.