Exotic fruit flies
What are they?
Fruit flies are the world’s worst pests of fruit and fruiting vegetables, causing millions of dollars worth of damage a year.
Australia has a number of native fruit flies, but most of these do not attack crops of economic significance. In contrast, exotic fruit flies present in neighbouring countries can infest commercial crops, causing crop devastation and trade disruption and requiring expensive eradication campaigns.
Early detection is the best means to achieve speedy and cost-effective eradication, and Australia has an extensive fruit fly surveillance program. Fruit fly traps are set in more than 1600 locations across Australia to monitor for exotic fruit flies, including trapping in remote northern locations by AQIS’s Northern Australian Quarantine Strategy (NAQS). Trapping also provides evidence to overseas trade partners of Australia’s freedom from particular fruit fly species.
Economically, the impact of a widespread exotic fruit fly outbreak would be felt across many sectors. International trade bans would cost millions of dollars in exports, the movement of fruit and vegetables across State borders would be further restricted and there would be extensive costs associated with the use of pesticides and other control measures.
The most likely way for fruit flies to enter Australia is in larvae-infested fruit. All commercial imports of fresh fruit are disinfested or are certified as being grown in a fruit fly free country or region. Non-commercial imports such as fruit carried by passengers arriving in Australia or in mailed parcels are destroyed.
What are their effects?
Fruit flies lay eggs in unripe and ripening fruit, where larvae hatch and feed on the fruit pulp. Infested fruit fails to ripen and spoils quickly. Flies can lay up to 800 eggs that grow to adulthood in three to five weeks.
What are the risks to Australia?
Several exotic fruit flies are of particular concern to Australia:
Papaya fruit fly
Papaya fruit fly (Bactrocera papayae) affects most commercial fruit including bananas, capsicums, chillis, citrus, guavas, mangoes, papaya and tomatoes. It is widespread in southern Thailand, East Malaysia, Singapore and Indonesia, and has become established in Papua New Guinea.
It is occasionally trapped in the Torres Strait Islands; an outbreak around Cairns, North Queensland in 1995 devastated local crops but was successfully eradicated in 1999. The eradication campaign cost $33.5 million — a small price to pay compared with predicted losses of more than $100 million a year in trade disruption alone.
Melon fly
Melon fly (Bactrocera cucurbitae) mainly affects plants such as cucumbers, pumpkins, rockmelons, squash, watermelons, but also chillies, green beans, mangoes, papayas, tomatoes, citrus and stone fruits.
It has a worldwide distribution including China, India, Hawaii, Japan, Malaysia, Papua New Guinea, Taiwan and Thailand. It is occasionally detected on islands in the Torres Strait but is not established in Australia.
Mediterranean fruit fly
Mediterranean fruit fly (Ceratitis capitata) is probably native to Africa. It can infest more than 200 fruits including avocado, bananas, capsicums, chillis, citrus, figs, custard apples, grapes, guavas, passionfruit, persimmons and pome and stone fruit. In Australia this pest only occurs in Western Australia.
Northern Australia Quarantine Strategy (NAQS) fact sheet on exotic fruit flies