Herbivore-induced volatile organic compounds emitted by maize: Electrophysiological responses in Spodoptera frugiperda females

Herbivory induces the emission of volatile organic compounds (VOCs) which are involved in the attraction of predators and parasitoids. In spite of the large number of studies that have addressed the electrophysiological and behavioral responses of natural enemies to herbivore-induced VOCs, whether herbivores perceive these compounds remains largely unknown. By coupling chemical and electrophysiological (Gas Chromatography–Mass Spectrometry GC–MS and Gas Chromatography–Electroantennography GC–EAG) techniques we identified individual compounds emitted by maize upon feeding by Spodoptera frugiperda Walker (Lepidoptera: Noctuidae) that elicit a response in conspecific females. Herbivory induced significantly the emission of β-myrcene, ( Z )-3-hexenyl acetate, ( E )-β-ocimene, β-linalool, ( E )-4,8-dimethyl-1,3,7-nonatriene [DMNT], indole, geranyl acetate, α-zingiberene, β-caryophyllene, ( E )-α-bergamotene, ( E )-β-farnesene, β-sesquiphellandrene, ( E )-nerolidol, and 4,8,12-trimethyl-1,3,7,11-tridecatetraene [TMTT]. From these, eleven compounds elicited a response in the antennae of S. frugiperda females (virgin and mated). The antennae of virgin and mated females responded consistently to ( Z )-3-hexenyl acetate, β-linalool, indole, ( E )-β-farnesene and TMTT. In addition the sesquiterpenes ylangene/(+)-cycloisosativene evoked a response in the antennae even though these compounds were not significantly increased upon herbivory. The numbers of antennae of virgin or mated females responding to individual compounds were similar even though a higher percentage of the antennae of gravid female tested responded to geranyl acetate. The results show that S. frugiperda detects several herbivore-induced VOCs emitted by maize plants. These compounds may be responsible for repellence previously observed in this species by volatiles induced by conspecifics.