Chemical composition of Rosmarinus officinalis (Lamiaceae) essential oils and evaluation of their toxicity against Bruchus rufimanus (Coleoptera: Chrysomelidae: Bruchinae) in Morocco

Abstract

AbstractControl methods used to limit field losses caused byBruchus rufimanusBoheman, 1833 consist of synthetic insecticides that pose health risks to farmers, consumers and the environment. In an attempt to find safer alternatives, we screened essential oils from the leaves ofRosmarinus officinaliscollected in the Middle Atlas and Loukkos regions of Morocco in the laboratory as natural fumigants againstB. rufimanus.These essential oils were extracted by steam distillation using a Clevenger distiller, characterised chemically by coupled gas chromatography–mass spectrometry (GC/MS) and tested at five concentrations (0, 10, 20, 40, 80 µl/l air). The essential oils ofR. officinalismainly comprised oxygenated monoterpenes (Middle Atlas: 79.4%; Loukkos: 48.78%) and terpenes (Middle Atlas: 14.71%; Loukkos: 32.33%). The lethal concentrations (LC50) of Middle Atlas and Loukkos essential oils against male beetles ranged from, respectively, 46.53 to 1.19 µl/l air and 58.85 to 11.57 µl/l air. Similarly, doses ofR. officinalisessential oils from Middle Atlas and Loukkos lethal to females, ranged from 44.6 to 2.08 µl/l air and from 53.00 to 5.38 µl/l air, respectively. Additionally, the lethal time (LT50and LT99) of exposed adults ranged from 1–8 and from 2–13 days for different concentrations ofR. officinalisessential oils from Middle Atlas and Loukkos, respectively. With no mortality recorded in the control groups, these findings demonstrate the fumigant potential of these oils against this bruchid under the storage conditions.