Exotic fruit fly surveillance

Background

Fruit flies are the world's most destructive fruit pests. Two of the most economically damaging in Australia are the native Queensland fruit fly (Bactrocera tryoni) and the introduced Mediterranean fruit fly (Ceratitis capitata).

Many species of fruit fly that do not exist in Australia would potentially cause major disruption to trade in horticultural products if they gained entry. Many of these species are present in countries that are near neighbours to Australia.

The papaya fruit fly outbreak in North Queensland in 1995 had a major impact on Queensland horticulture. It cost many millions of dollars to eradicate and for growers to meet quarantine restrictions for export. Continuing vigilance is required to reduce the possibility of a major fruit fly outbreak occurring again. This is provided by a network of fruit fly traps throughout high-risk areas of Queensland as part of a national surveillance system.

This network also provides evidence to trading partners of Queensland's and Australia's continuing freedom from exotic fruit fly. Some export destinations will not accept produce without this evidence.

The trapping network

The trapping network consists of strategically placed traps in high-risk locations in Queensland. High-risk locations are areas that are most likely to be initially infested with fruit fly should it gain entry. These include urban areas associated with international ports, and remote parts of Cape York Peninsula.

Cape York Peninsula is a risk because of its proximity to Papua New Guinea, which is infested with a number of fruit flies of quarantine concern, including papaya fruit fly and melon fly. Outbreaks of these species also occasionally occur on some Torres Strait islands, which have an ongoing fruit fly containment program. The trapping is based on national and international protocols.

The traps

The trap types used are lynfield (low rainfall areas) and steiner (high rainfall areas). They consist of a plastic container with openings (ports) to allow fruit fly entry as well as a wire hook for attaching the wick. The wick consists of absorbent dental cotton rolls to which a mixture of lure and insecticide is applied.

When the trap is suspended from host trees, the lure and insecticide mixture attracts the fly into the trap and kills it. The dead fly is then caught in the bottom of the trap. Several different lure/insecticide mixtures are used in different traps to attract a wide selection of important exotic species.

The trap catch

Several native fruit fly species are abundant in Queensland and are also caught in fruit fly traps. The differences between fruit fly species are slight and not usually evident to the untrained observer or the naked eye.

Biosecurity Queensland trap inspectors visit fruit fly traps fortnightly. Trained Biosecurity Queensland staff then remove any flies caught and send them to a central laboratory for identification. Trained volunteers visit some traps in remote areas less frequently.

Reporting

Results from each week's trap run are recorded in a computer database and reported to the Office of the Chief Plant Protection Officer in Canberra.

The detection of an exotic fruit fly triggers the implementation of a contingency plan to delimit the incursion and possibly eradicate the species should an outbreak occur.

It is essential that members of the public do not handle or open fruit fly traps.