Border security for fruit flies

A discovery that enables the most economically important fruit fly species to be identified from their DNA 'signature' could avert future devastating fruit fly outbreaks, according to scientists from the NSW Department of Primary Industries (DPI).

Molecular biologists and entomologists from the DPI have developed the means to identify selected species of fruit fly from segments of their DNA. This enables fruit fly to be developed from larvae or incomplete adults.

Molecular biologist Dr Deb Hailstones said the discovery greatly increased the likelihood of an outbreak of fruit fly being contained early.

"Previously, fruit fly species could only be identified accurately visually from mature adults," she said. "This meant there could be a delay of weeks before an accurate assessment can be made of a species, and whether it is an economic threat."

The new method of identification relies on use of a molecular key development by DPI entomologist, Peter Gillespie.

Hailstones said the key sets out a means for amplifying and comparing target sections of DNA that the different species of fruit fly have in common.

"It is not yet able to distinguish between the hundreds of species of fruit flies known to damage fruits and vegetables. However we can identify patterns of DNA that are typical of the 30 species of greatest significance for Australian horticulture."

The technique enables this group of economically important species to be identified from larvae or from incomplete adults.

Older methods require fruit flies to be identified morphologically, meaning that specimens of adult flies have to be supplied - and they have to be complete.

Hailstones said the molecular key will be useful for border surveillance and quarantine and for the problem specimens where eggs or early maggots are found in produce.

"Instead of fruit rotting at borders or in quarantine while scientists wait until visual tests can be done, the insects can be identified from their DNA almost immediately", she said.

The key has been proposed as an Australian standard and will be updated as soon as new discoveries are made.

Fruit flies are amongst the world's most destructive horticultural pests and a major outbreak can cost many millions of dollars. In 1995 in north Queensland, an outbreak of papaya fruit fly cost industry an estimated $100 million.

The research was undertaken by staff from the Agricultural Scientific Collections Unit in Orange and the Elizabeth Macarthur Agricultural Institute.

Joanne Finlay is a science communication specialist with the NSW Department of Primary Industries.