Evaluating the risk of the establishment of screwworm fly in Australia

Objective To investigate probabilities of establishment of screwworm fly throughout the year, for several locations around Australia's coastline. Methods A simulation model that predicts the spread and economic impact of an established screwworm fly population was modified to include stochastic survival functions, to investigate the risks of the pest actually establishing in this country. The effects of time of year, climate, vegetation and the number of incoming flies or larvae were investigated for four locations around Australia. Results Analysis of variance identified a dominant three-way interaction between site, time, and the number of introduced flies. These probabilities are graphed. Discussion In southern areas, as exemplified by Fremantle, the cold winters limit survival. A high probability of establishment exists year round in tropical regions, except in areas around the Gulf of Carpentaria and in the Northern Territory where dry weather mid-year would limit survival. Despite these comparatively lower risks, there were no areas or times where reductions in quarantine efforts could be justified.