Synergized potential, insecticidal and repellent activity of essential oils from two Rhododendron species against three stored product insects. Issue 1 (2nd January 2023) - Feng, Yi-Xi
ABSTRACT: In this work, the essential oils (EOs) from leaves and flowers of Rhododendron spinuliferum and Rhododendron spiciferum were extracted by hydrodistillation, chemical compositions of EOs were analyzed by GC-MS and GC-FID. For R. spinuliferum and R. spiciferum, α- and β-pinene were common major compounds. It provided an opportunity to test the potential synergistic effect of α- and β-pinene among EOs. Firstly, four EOs and two major compounds (α- and β-pinene) exhibited fumigant, contact and repellent activities to three stored-product insects. To the red flour beetle, leaves of both species exhibited stronger contact toxicity than flowers did. This trend was diverse to the booklouse. Furthermore, binary mixture bioassays of α- and β-pinene were performed following natural proportions. Results of multiple linear regression showed that α-pinene, trans-β-farnesene and bornyl acetate were responsible for the contact toxicity to the red flour beetle and booklouse with diverse contribution.