Chemical composition and insecticidal activities of Laurus nobilis (L.) essential oilsfrom Tunisia and Morocco against adults of the lesser grain borer,Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae)

Abstract: Historically, cereal production has always been an important component of Tunisianand Moroccan agricultures. Durum wheat is the major crop and the most widely cultivated cereal.During varied storage conditions, wheat grains are attacked by a large number of insect pests.Among these, the lesser grain borer Rhyzopertha dominica Fabricius. It is one of the mostimportant internal feeders of stored grain. It is a major, primary pest of stored products. Adult R.dominica feed on many kinds of grains including rice, wheat, millet, and sorghum. This pest isamong the main stored-product pests in Tunisia and North Africa. The management of this insectis mainly based on chemical control. However, serious problems have been identified for thefuture of chemical methods of grain disinfestations. Thus, there is an urgent need to find out analternative strategy to control this pest. In this work, we report the assessment of repellent andfumigant activities of Laurus nobilis essential oil from Tunisia and Morocco against adults R.dominica and we investigate their chemical composition. Essential oils chemical compositionassessed via GC and GC/MS analysis showed 1,8 cineole (24.55-38.86%), linalool (17.67-9.45%), eugenylmethylether (12.40-3.93%), isovaleraldehyde (9.65-10.47%) and α-pinene (2.52-4.31%) were the major common compounds. The two essential oils exhibited important fumigantand repellent activities against the pest. Activities varied with the oil concentration and theexposure time. R. dominica was more sensitive to Moroccan oil than Tunisian oil. LC50 valueswere respectively 3.58 and 4.31μl/l air whereas the LC95 values were 4.26 and 6.37μl/l air. Inaddition, percentage repellency (PR) values were 60% and 72.5% after 24h of exposure at theconcentration 0.12μl/cm2 respectively for Tunisian and Moroccan oil.