toxicity and repellency effects of three essential oils against tetranychus urticae koch (acari: tetranychidae)

two-spotted spider mite, tetranychus urticae koch (acari: tetranychidae), is one of the most injurious pests of fruits, vegetables and ornamental plants worldwide, both outdoor and indoors. currently the main method of control of this pest is through application of pesticides which is mostly accompanied by the resistance of the pest against pesticide(s). the resurgence of resistant mite populations brings about further contamination of foodstuff and environment. essential oils obtained from the aerial parts of plants may have the potential to be an alternative to synthetic pesticides, since they have been demonstrated to posses a wide range of bioactivities against insects and mites. so, the aim of the current study was to investigate the effect of essential oils extracted from three different medicinal plants namely: mentha longifolia, salvia officialis (both lamiaceae) and myrtus communis (myrtaceae) against t. urticae. the lc50 values of essential oils of m. longifolia, m. communis, and s. officialis against t. urticae were 20.08, 53.22, 60.93 µl l-1 air, respectively. this shows that m. longifolia possesses the highest lethal activity whereas s. officialis the lowest. also, essential oils of m. longifolia, m. communis, and s. officialis were demonstrated to possess repellency effect with ed50s of 147.47, 138.80 and 164.41, µl l-1 air, respectively. these data suggest that essential oils of all the three plants have the potential to be employed in the pest management programs designed for a control of t. urticae under greenhouse conditions.