François Verheggen - Thématiques de recherche
Aphid and Plant Secondary Metabolites Induce Oviposition
in an Aphidophagous Hoverfly
Abstract - Episyrphus balteatus DeGeer (Diptera, Syrphidae) is an abundant and efficient aphid specific predator but usually neglected in integrated pest management programs. Electrophysiological experiments were conducted for the first time on E. balteatus in the present work, toward the common aphid alarm pheromone, (E)-β-farnesene (EβF), as well as on a broad range of plant secondary metabolites, including terpenoids (mono- and sesquiterpenes) and green leaf volatiles (C6 and C9 alcohols and aldehydes). Monoterpenes induced significant EAG responses, whereas sesquiterpenes were found to be inactive on EAG, except for the aphid alarm pheromone (EβF). The most pronounced antennal responses were induced by six and nine carbon green alcohols and aldehydes (i.e. (Z)-3-hexenol, (E)-2- hexenol, (E)-2-hexenal and hexanal). To investigate the behavioral activity of the EAG active plant and aphid secondary metabolites, observations were conducted on E. balteatus females exposed to three compounds: R-(+)-limonene (monoterpene), (Z)-3-hexenol (green leaf alcohol) and EβF (sesquiterpene, common aphid alarm pheromone). A single E. balteatus gravid female was exposed for 10 min to a Vicia faba plant which was co-located with a semiochemical dispenser. Without additional semiochemical, hoverfly females were not attracted toward the plant and no oviposition was observed. The monoterpene R-(+)- limonene had no impact on the foraging behavior of the tested females, whereas (Z)-3- hexenol and EβF increased the time of flight and acceptance of the host plant. Moreover, these two chemicals induced the oviposition of gravid females on aphid-free plants, suggesting that the selection of the oviposition site by predatory hoverflies relies on the perception of chemical blend composed by both prey pheromones and secondary metabolites induced in the host plant.
Keywords - Episyrphus balteatus • Predator • Plant-insect interaction • Oviposition induction • Green leaf volatiles • Terpenoids • (E)-b-Farnesene • Electroantennography • EAG
Référence - François J. Verheggen, Ludovic Arnaud, Stefan Bartram, Marie Gohy and Eric Haubruge (in press). Aphid and plant secondary metabolites induce oviposition in an aphidophagous hoverfly. Journal of Chemical Ecology