Evaluation of contact toxicity of ten essential oils from Lamiaceae plants against Tetranychus urticae Koch (Acari: Tetranychidae)

Two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is an important pest of greenhouse, vegetables and ornamental crops. The mite management is commonly based on the repetitive applications of pesticides, resulting in environmental pollution and resistance in pest population. In recent years, essential oils, plant extracts and plant secondary metabolites have received much attention as pest controlling agents because of their insecticidal, acaricidal, repellent and antifeedant properties. In the present study, contact toxicity of the essential oils from ten Lamiaceae plants were evaluated against adults of T. urticae. Bioassays were carried out in 4 concentrations (200, 400, 800 and 1600 ppm). The essential oils were obtained by hydrodistillation using modified Clevenger-type apparatus. Adults\' mortality was determined 24 hour after treatment and the LC50 values of the essential oils were evaluated. Results showed that the essential oils from Zataria multiflora and Mentha piperita with LC50=419.44 mg/L and LC50=425.42 mg/L were the most toxic on T. urticae. Essential oils from ten Lamiaceae plants showed acaricidal activities in a dose-dependent manner. The tested essential oils had no phytotoxicity at concentrations less than 1600 ppm and low phytotoxicity at 1600 ppm.