Electrophysiological and Behavioral Responses of Phthonoloba viridifasciata (Lepidoptera: Geometridae) to Volatiles from Alsophila spinulosa

Phthonoloba viridifasciata (Lepidoptera: Geometridae) is the primary herbivorous insect of the rare and endangered plant Alsophila spinulosa. The aim of this study was to investigate the host-seeking mechanism of P. viridifasciata by screening volatile compounds from A. spinulosa for their attractant or repellent activity, so as to provide a theoretical basis for its eco-friendly control. We used the dynamic headspace adsorption to collect the volatile compounds from A. spinulosa. A combination of Gas Chromatography–Electroantennography Detection (GC-EAD), Gas Chromatography–Mass Spectrometry (GC-MS), electroantennography (EAG), and Y-olfactometer bioassays was used to screen and identify active compounds that induce responses in P. viridifasciata. Five active volatile compounds induced significant electrophysiological activity, including decane, undecane, 4-ethylbenzaldehyde, m-ethylacetophenone, and p-ethylacetophenone. All five active compounds triggered EAG responses in both sexes. Behavioral bioassays further revealed that 4-ethylbenzaldehyde (10−2 and 10−4 mol/L) and decane (10−5 mol/L) act as female attractants. Meanwhile, males showed a behavioral preference response to 4-ethylbenzaldehyde at 10−2 mol/L.