Chemical Composition of Essential Oils from Three Rhododendron Species and Their Repellent, Insecticidal and Fumigant Activities.

In order to assess the repellent, contact, and fumigant properties of three essential oils (EOs) from Rhododendron species in China against adults of Tribolium castaneum, Lasioderma serricorne, Sitophilus oryzae, this study analyzed their chemical components. The three EOs were extracted by hydrodistillation from leaves of Rhododendron species, including R. davidsonianum, R. heliolepis and R. strigillosum. Sesquiterpenoids and monoterpenes were the main components of the three EOs that were detected by GC/MS and GC-FID. α-Pinene, β-Caryophyllene, α-Humulene, Kaura-16-ene and Sandaracopimaradiene was among the comparatively high components. In this study, the EOs of three Rhododendron species demonstrated repellent activities against T. castaneum and L. serricorne in 2 h and 4 h exposure, but the repellent activity to S. oryzae was not obvious. The three EOs from R. davidsonianum, R. heliolepis and R. strigillosum also had contact activities and fumigant activities against the Tribolium castaneum (LC =13.453 mg/L air, 4.728 mg/L air, 4.529 mg/L air and LD =15.027 μg/adult, 15.017 μg/adult, 10.994 μg/adult, respectively), Lasioderma serricorne (LC =8.584 mg/L air, 6.044 mg/L air, 6.355 mg/L air and LD =4.566 μg/adult, 7.067 μg/adult, 3.652 μg/adult, respectively) and Sitophilus oryzae (LC =3.304 mg/L air, 6.795 mg/L air, 7.130 mg/L air and LD =10.200 μg/adult, 15.021 μg/adult, 9.178 μg/adult, respectively) adults. The above results not only opened a potential prospect for applications of Rhododendrons in the prevention and control of insects in stored products, but also provide a basis for the comprehensive utilization of the rich natural Rhododendron plant resources.