Epsilon Open Archive

Abstract

Over the last few years, several tephritid species have invaded sub-Saharan Africa, competitively displacing native fruit fly pests, and severely affecting horticulture production. In two different farming scales, small and large, we verified the influence of suppressing the invasive Bactrocera dorsalis using the male specific attractant, methyl eugenol (ME), formulated in SPLAT-spinosad. In small-scale farm plots, use of ME did reduce B. dorsalis populations, but population levels remained high throughout the study. In mark-release-recapture studies, male flies were found to disperse fast and beyond one km from the release point. In large-scale farm plots, the invasive pest was controlled within eight months of suppression using ME-based suppression in combination with other pest management techniques. However, this was paralleled by a quick resurgence of the native fruit fly Ceratitis capitata, likely due to competition release. Targeting female fruit flies using techniques that rely on the olfactory sensitivity of the flies, may support direct and more selective ways to control fly populations. Host fruits, as well as proteins produced during fermentation, are important resources for tephritid fruit fly nutrition and reproduction. This study used gas chromatography-coupled electroantennography detection (GC-EAD) to test the physiological response of economically important tephritid pest species to host fruits and commercially available food-baits. This was compared to the published database of odorant receptors of Drosophila melanogaster. We postulated that volatiles shared across fruits and detected by several fly species may comprise general fruit compounds important in host orientation. Selected blends, composed of 6 or 11 fruit compounds were more attractive to B. dorsalis than full fruit odor in a multi-choice olfactometer assay. Species-specific and general blends identified from food-baits were more attractive to B. dorsalis. The study underlines the potential of a comprehensive database of olfactory sensitivity in the rational design of novel synthetic attractants, or for augmenting existing ones. The study also provides a platform to develop both species-specific attractants and multi-species attractants for tephritid fruit flies.

Keywords: Bactrocera dorsalis, food-baits, fruit volatiles, GC-EAD, male lures, olfactometer, Tephritidae