Species composition and dispersal of nuisance flies breeding on egg farms in southern Australia

The vectorial and dispersal capacities of flies make them a biosecurity and food safety risk on egg farms. The design of optimal control and biosecurity programs requires knowledge of species composition and patterns of abundance of the fly populations present. Although there have been many studies of flies breeding on egg farms in other countries there is little information available in Australia. We monitored numbers and species of flies breeding on cage egg farms in southern Australia and used mass marking with fluorescent resin dye to assess the dispersal of the major species from one of the farms. The main peak in fly numbers occurred in spring and early summer and was comprised predominantly of little house flies (Fannia canicularis). Significant numbers of false stable flies (Muscina stabulans) were trapped near accumulated manure, but relatively low numbers were present in bird housing areas. House flies (Musca domestica) were found in only low numbers or were absent at most times of the year. In the dispersal studies, 85% of marked F. canicularis and 67% of marked M. stabulans were trapped within 255 m of the layer sheds. The greatest distance from the farm at which marked F. canicularis flies were captured was 739 m for traps and 1.25 km for tapes whereas M. stabulans flies were trapped at all distances including in the most distant trap nearly 2 km from the farm. Modelling of trap catches by distance predicted maximum dispersal distances of 1.6 km for F. canicularis and 2.4 km for M. stabulans.