Sesquiterpenoid-rich Essential Oils from Two Magnolia Plants: Contact and Repellent Activity to Three Stored-product Insects
Stored products have been damaged by insects. Multiple approaches for pest management are employed. Among these approaches, botanical insecticide is an emerging one. This work investigated the pest management potential of Magnolia coriacea and Magnolia macclurei essential oils (EOs) to three major stored-product insects, namely the red flour beetle, cigarette beetle and booklouse. Magnolia coriacea and M. macclurei EOs showed promising contact toxicity to the cigarette beetle, with LD50 values of 11.7 and 12.3 μg/adult. The contact toxicity of M. coriacea EOs to the booklouse (LC50 = 95.5 μg/cm2) was much stronger than that of M. macclurei EOs (LC50 = 245.4 μg/cm2). To explore the contribution of individual compounds to insecticidal activity of EOs, chemical analysis was performed by GC-MS. Results showed that nerolidol (27.84%), agarospirol (18.34%), elixene (15.84%) and helminthogermacrene (12.69%) were major compounds of M. coriacea EOs, β-guaiene (60.31%) and elixene (20.42%) dominated in M. macclurei EOs. Nerolidol and β-guaiene showed contact activity to three insect species. Nerolidol showed stronger contact toxicity to the red flour beetle and cigarette beetle than M. coriacea EOs did, both samples were similar to the booklouse. β-Guaiene was much stronger to the red flour beetle and booklouse, but weaker to the cigarette beetle than M. macclurei EOs did. The repellent effects of EOs and compounds were at various levels. Generally, results suggested that the contact toxic potential of samples could serve as management for the cigarette beetle and booklouse, while repellent effect would be used to control the red flour beetle.
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