Insecticidal Activities of the Forsythia Suspensa Essential Oil Against Two Tobacco Storage Insects

Bioactivity screening was conducted in order to develop new botanical pesticides against tobacco storage pests. The essential oil obtained from the fruits of Forsythia suspensa was investigated by GC-MS. A total of 18 components representing 94.30% of the oil were identified and the main compounds in the oil were found to be α-pinene (63.72%), b-terpinyl acetate (7.47%), 4-terpineol (6.67%), 3-isopropyltoluene (3.54%) and γ-terpinene (2.54%). It was found that the essential oil exhibited strong fumigant toxicity against Lasioderma serricorne and Tribolium castaneum adults with LC₅₀ values of 8.94 and 7.68 mg/L air. Meanwhile, the essential oil exhibited contact toxicity against T. castaneum and L. serricorne adults with LD₅₀ values of 23.66 and 30.13 μg/adult. Among the three individual compounds, 4-Terpineol showed the strongest fumigant and contact activities (LC₅₀=6.90 mg/L; LD₅₀=8.62 μg/adult) against L. serricorne. Meanwhile, α-pinene, γ-terpinene and 4-terpineol exhibited strong bioactivities against T. castaneum. The results indicated that the essential oil of F. suspensa and its isolated compounds have the potential to be developed into natural insecticides for controlling insects in stored tobacco.