Attraction of Frankliniella occidentalis Females towards the Aggregation Pheromone Neryl (S)-2-Methylbutanoate and Kairomones in a Y-Olfactometer

SIMPLE SUMMARY: Understanding insect olfactory perception can lead to more effective and specific ways to manage pests. In fact, odors have two components: (1) the quality, defined as its chemical composition, and (2) the quantity, defined by the concentration of the odor. The quantitative aspect is often missing and we aim to provide valuable information on the quantitative aspect of the odors that attract the western flower thrips, an insect that damages crops. In this study, we tested how the western flower thrips responded to different odors in an olfactometer. We measured the odor concentrations carried by the air and found that the thrips were most attracted to a pheromone at very low concentrations, much lower than the other odors we tested. Our results show that the attraction of western flower thrips to an odor depends on its quantitative aspect and could help to develop better ways of managing this pest. ABSTRACT: An understanding of insect olfaction allows for more specific alternative methods of pest control. We evaluated the responses of the western flower thrips (WFT, Frankliniella occidentalis) in a Y-olfactometer to estimate gas-phase concentrations of the aggregation pheromone neryl (S)-2-methylbutanoate and known kairomones such as methyl isonicotinate, (S)-(-)-verbenone, and p-anisaldehyde. The gas-phase concentrations of these compounds were obtained from the release rates measured in dynamic headspace cells. The compounds were collected from the headspace using dried solid-phase extraction (SPE) cartridges and analyzed with a triple quadrupole GC-MS/MS. We observed that the aggregation pheromone significantly attracted WFT females at doses of 10 and 100 µg, whereas methyl isonicotinate and p-anisaldehyde significantly attracted WFT females at the highest dose. Verbenone did not produce any significant results. A completely different picture was obtained when the gas-phase concentrations were considered. The minimal gas-phase concentrations of the pheromone required to attract WFT females was 0.027 ng/mL, at least 100 times lower than that of the other two compounds. The relevance and implications of our results are discussed in light of the insect’s biology and pest management methods.