Recruitment of Hippodamia variegata by active volatiles from Glycyrrhiza uralensis and Alhagi sparsifolia plants infested with Aphis atrata.

Background: Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae), a dominant predatory natural enemy species in cotton-planting, is a key biological control agent for aphids in China. Our previous study showed that herbivore-induced plant volatiles (HIPVs) from Glycyrrhiza uralensis (Fisch.) (Fabales: Fabaceae) and Alhagi sparsifolia (Desv.) (Fabales: Fabaceae) plants infested with Aphis atrata (Zhang) (Homoptera: Aphididae), were important semiochemicals for Hippodamia variegata to locate aphids. However, little was known about the varieties and function of active volatiles from HIPVs of the two plant species.

Results: In this study, results from gas chromatography-electroantennography detection (GC-EAD) demonstrated that seven HIPVs (butyl acrylate, α-pinene, butyl isobutyrate, β-pinene, butyl butyrate, 1,3-diethylbenzene and 1,4-diethylbenzene) identified from the two damaged plant species elicited antennal responses from Hippodamia variegata. Also, results from gas chromatograph-mass spectrometry (GC-MS) analysis showed that the concentrations of the seven active volatiles were significantly higher than those from corresponding healthy plants. Hippodamia variegata exhibited varying degrees of response to each active volatile in electroantennography (EAG) trials, however, only α-pinene, butyl isobutyrate, β-pinene and butyl butyrate significantly attracted Hippodamia variegata in behavioral trials conducted in the laboratory. They also had a better trapping effect on Hippodamia variegata in cotton fields.

Conclusion: Four active compounds (α-pinene, butyl isobutyrate, β-pinene and butyl butyrate) identified from two damaged plant species were considered the most effective HIPVs that attract Hippodamia variegata. These findings provide possibilities for the development of Hippodamia variegata attractants. They also provide a theoretical basis for the biological prevention and control of aphids using Hippodamia variegata. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.