Dactylopius opuntiae of cactus pear in Morocco: contact and fumigant insecticidal activities of four essential oils and hydrosols and their chemical composition

Abstract

Morocco's prickly pear has high economic value. However, it’s infected by the cochineal Dactylopius opuntiae, causing massive losses. Thus, the present work aims to study insecticidal effect of bioactive natural extracts. Essential oils and hydrosols of oregano (Origanum vulgare), thyme (Thymus vulgaris), pennyroyal (Mentha pulegium) and peppermint (Mentha piperita) were tested. Two concentrations were used for essential oils (1.5% and 3%) and for hydrosols (100% and 75%) with contact and fumigant application. Mortality rate was determined after 24h of treatment. Highest values were recorded at 3% E.O concentration with contact assay comparing to fumigation. As it’s EO (99.44%), O. vulgare hydrosol has significant insecticidal activity reaching 80% of mortality rate. Chemical composition of essential oils using Gas Chromatography coupled to Mass Spectrometry (GC/MS) was studied. Bioactive compounds include carvacrol and m-cymene (O. vulgare and T. vulgaris), pulegone and l-menthone (M. pulegium) and Linalool and linalyl acetate (M. piperita). Data obtained relieved the importance of these plants as source of natural bioactive compounds against D. opuntiae.