Raspberry Ketone Increases Survival and Reduces Sterile Male Bactrocera tryoni Froggatt Response to Cue-lure: Implications for Sterile Insect Technique Programmes

Background: Semiochemicals are chemicals produced by one organism that incite a response in another organism. They have been used to enhance male performance of tephritids of the genera Anastrepha, Bactrocera and Ceratitis and include fruit or plant volatiles and oils. In Australia, the cue-lure (a derivative of the naturally occurring phenylpropanoid, raspberry ketone (4-(4-hydroxyphenyl)-2-butanone)) responding Queensland fruit fly, Bactrocera tryoni (Froggatt), is the most significant horticultural pest, attacking most commercial fruits and many fruiting vegetables. Among the different management options for this pest, the sterile insect technique (SIT) and cue-lure-based male annihilation technique (MAT) are regarded as two of the most effective methods, particularly when used under an Area Wide Management scenario. However, the combination of these two methods has been considered incompatible in B. tryoni management (as the MAT are thought to kill the sterile males).

Methodology: In the present study we tested the mortality and survival of raspberry ketone (RK)-fed adult sterile B. tryoni released in field cages (diet contained 0, 0.5, 1 and 2% RK) and in the field across two commercial orchards, one comprising a single stone fruit variety, the other comprising multiple stone fruit varieties (diet contained 0.2% RK), respectively. We also assessed the response of RK-fed sterile male B. tryoni to cue-lure in field cages and across two commercial orchards as described above.

Results: Mortality of flies in field cages was lower for RK-fed flies. Similarly, survival of flies under orchard conditions was higher for RK-fed flies than non-RK-fed flies. Data suggest a lower recapture of RK-fed sterile males than non-RK-fed sterile males in cue-lurebaited Lynfield traps in both the field cage and orchard trials. The advantage of this “male replacement” approach (mortality of wild males at lure-baited traps while simultaneously releasing sterile males) lies in the significant increase of sterile to wild male overflooding ratios, and the possibility of reducing the required number of sterile males to be released.

Conclusion: Although further research is still required, ultimately, management of B. tryoni could effectively combine MAT and SIT.