Chemical Composition of Essential Oils from the Leaves of Schinus molle and Cupressus sempervirens and their Insecticidal Activity against Oryzaephilus surinamensis (Coleoptera: Silvanidae)

Abstract

Essential Oils (EOs) from aromatic plants were reported to have an insecticidal activity against several insects and could be an alternative to synthetic insecticides. The aim of this study is to determine the chemical composition of two plants (Schinus molle and Cupressus sempervirens) grown in Algeria and to investigate their insecticidal activity against the sawtoothed grain beetle Oryzaephilus surinamensis, a secondary pest that may alter seriously the proprieties of some food products. EOs were extracted by hydrodistillation using Clevenger apparatus and analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). The analysis determined that the major components of S. molle EO are β-Eudesmol (15.19 %), Elemol (13.97 %), D-Limonene (9.89 %), Spathulenol (9.33 %) and β-Phellandrene (7.72 %) while those of C. sempervirens EO are Cedrol (44.81 %), α-Pinene (15.71 %) and neoiso-Dihydrocarveol acetate (9.7 %). The biological activity of EOs was evaluated by fumigation and repellency at different concentrations and exposure times. Fumigation toxicity bioassays showed maximum efficacy was reached at a concentration of 100 μL/L of air for the two kinds of EOs (90-100 %). Repellency tests revealed that S. molle EO was moderately repellent (55.62 %), while C. sempervirens EO was highly repellent (66.25 %). In fact, the EO of the experimental plants can be incorporated into insecticidal formulations and might be efficient as alternative to synthetic insecticides for O.surinamensis control. However, other tests need to be performed on other life stages of the insect.