Fumigant toxicity of cumin, spearmint and lavender essential oils against eggs and adults of two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

Two-spotted spider mite, Tetranychus urticae Koch is one of the most important pests of orchard trees, vegetables and ornamental crops worldwide. Frequent chemical pesticide applications have caused development of resistance, undesirable effects on non target organisms and environmental pollutions. Plants are rich sources of secondary metabolites with pesticidal properties which can be a suitable alternative to chemicals in pest’s management. In this study, fumigant toxicity of three medicinal plant essential oils including cumin (Cuminum cyminum L.), spearmint (Mentha spicata L.) and lavender (Lavandula stoechas L.) were tested against eggs and female adults of T. urticae. The essential oils were obtained by Clevenger-type water distillation. Experiments were carried out at 25±1°C, 50±5% RH and under a photoperiod of 16L: 8D. The median lethal concentration (LC50) for the essential oils from cumin, spearmint and lavender essential oils were 19.762, 20.929 and 34.534 µl/L air, 24h. after treatment, respectively. In ovicidal bioassays, the calculated LC50 values for oils were 40.585, 19.714 and 30.953 µl/L air, respectively. The results showed that cumin oil had the highest adulticidal effect in comparison with other essential oils, but there were no significant differences between the lethal effect of cumin and spearmint essential oils. Also spearmint oil had significantly the highest lethal effects against eggs of T. urticae than the other two essential oils.