In the 1999-2000 season, there were widespread outbreaks of Queensland fruit fly (Q-fly) in the Fruit Fly Exclusion Zone (FFEZ), affecting especially the Riverina region. In subsequent seasons, outbreaks have continued to plague the FFEZ. In order to combat these outbreaks, we need to know where these outbreak flies are coming from.

This project was initiated in order to use DNA fingerprinting technology to identify the sources of the outbreak flies. The main part of the project involved building an extensive database of DNA profiles from all possible source populations. For this, we collected samples from Brisbane in the north to Wodonga in the south, west to Alice Springs and within the FFEZ itself. A large number of samples were also collected along the Western Slopes of NSW. At least 8 distinct potential source populations were identified. Significantly, at least 4 of these were established in the FFEZ.

We then analysed the DNA fingerprints of outbreak flies from the FFEZ. Our results showed that between 2002 and 2004:

• most outbreaks could be tracked to nearby sources. There was little indication that outbreak flies were arriving directly from Sydney, Brisbane or other coastal sites.
• the major source of outbreak flies was the population from the Wagga-Albury region;
• the population in Deniliquin was also a significant source of outbreak flies; and
• there appeared to be considerable movement of flies along the Murray Valley.

In previous years, Q-fly control in NSW has concentrated on the region north of Wagga. The relatively few flies entering the north-eastern corner of the FFEZ may reflect the effectiveness of those control measures. Nevertheless, the Wagga-Albury region and Deniliquin are currently major sources of outbreaks in the FFEZ and should attract equal control efforts. Our results also suggest that local traffic (as opposed to long-distance travelers from the east coast) may be the major route by which Q-fly disperse and enter the FFEZ.

This project has been funded by Hort Innovation, using the research and development levies listed below and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

• Vegetable Fund
• Potato – Processing Fund
• Potato – Fresh Fund
• Onion Fund