Fruit fly monitoring programs are vital to protect Australian horticultural industries from exotic fruit fly incursions and to maintain market access for producers within Pest Free Areas of production. Traps containing lures specific to male fruit flies generally predominate in these programs due to the impracticality of existing female fruit fly lures. However, the supplementary use of female fruit fly lures in monitoring programs could greatly improve the chances of detecting an incursion, particularly of some exotic species where male flies are not responsive to lures.

Fruit flies require dietary protein to become sexually mature. Therefore, most existing female fruit fly lures are food-based attractants such as proteins or products of protein degradation. The most common female lure used in Australia consists of 2% aqueous yeast autolysate deployed in a McPhail trap. This lure has a number of disadvantages: it needs to be replaced weekly; it’s unpleasant to handle; attractive to non-target insects; and causes deterioration of fruit fly specimens drowned in the liquid. Alternative lures for female fruit flies that could overcome these shortfalls were developed and/or evaluated during this project.

Two prototype food-based lures were developed at the beginning of the project. One was a gel lure with the consistency of agar; the other a dry lure made by applying a liquid lure to vermiculite. These lures were tested in series of laboratory, outdoor cage and field trials on a range of Bactrocera sp. and Ceratitis capitata. In NSW, the prototype lures were compared to yeast autolysate lure (standard female lure for Bactrocera sp.), whereas in WA, the lures were compared to 3-component Biolure (standard female lure for C. capitata).

Controlled laboratory data demonstrated that only a small proportion (~20%) of female Bactrocera tryoni are attracted to proteinaceous lures. Observational field data also suggested that all the female lures tested attracted only a small proportion of the predicted B. tryoni and C. capitata populations, as indicated by captures of flies in traps charged with male lures. Similar observations have been reported for other fruit fly species, but in the absence of more reliable cues for female fruit flies, the current project aimed to overcome the disadvantages of the current yeast autolysate lure, while maintaining a similar level of attractiveness.

In all field tests, the dry lure performed very poorly compared to other lures, capturing significantly lower numbers of flies under all environmental conditions. The standard lures (yeast autolysate or Biolure) also outperformed the gel lure in terms of the number of captures in most, but not all, field tests. The real advantages of the gel lure compared to the yeast autolysate lure was evident in the longevity of the lure (lasting up to 12 weeks), the reduced captures of non-target insects such as blowflies and moths, and the improved quality of fruit fly specimens captured due to reduced humidity and decomposition within the trap. Because of the importance of these advantages, it may be worthwhile to invest in the enhancement of the gel lure chemistry and/or trap technology in the future.