Insecticidal Activity of the Leaf Essential Oil of Peperomia borbonensis MIQ. (Piperaceae) and Its Major Components against the Melon Fly Bactrocera cucurbitae (Diptera: Tephritidae)

The essential oil from the leaves of Peperomia borbonensis from Reunion Island was obtained by hydrodistillation and characterized using GC-FID, GC/MS and NMR. The main components were myristicin (39.5%) and elemicin (26.6%). The essential oil (EO) of Peperomia borbonensis and its major compounds (myristicin and elemicin), pure or in a mixture, were evaluated for their insecticidal activity against Bactrocera cucurbitae (Diptera: Tephritidae) using a filter paper impregnated bioassay. The concentrations necessary to kill 50% (LC50) and 90% (LC90) of the flies in three hours were determined. The LC50 value was 0.23 +/- 0.009 mg/cm(2) and the LC90 value was 0.34 +/- 0.015 mg/cm(2) for the EO. The median lethal time (LT50) was determined to compare the toxicity of EO and the major constituents. The EO was the most potent insecticide (LT50 = 98 +/- 2 min), followed by the mixture of myristicin and elemicin (1.4: 1) (LT50 = 127 +/- 2 min) indicating that the efficiency of the EO is potentiated by minor compounds and emphasizing one of the major assets of EOs against pure molecules.