Toxicity and repellency effects of three essential oils on two populations of Tetranychus urticae (Acari: Tetranychidae)

Essential oils are environmentally benign agents which are used as alternative compounds for chemical pesticides in order to control pests. Thus, in the current study, the toxicity and repellency effects of essential oils, extracted from three medicinal plants of the Lamiaceae family, including Thymus daenensis, Satureja khuzestanica, and S. bakhtiarica, were evaluated against a resistant (MhR) and a susceptible (KrS) population of Tetranychus urticae. Results based on probit analysis revealed that all extracted essential oils to some extent showed both repellency and toxicity effects on both populations of the mite. The LC50 values of S. khuzestanica extract were the lowest against the both populations (31.16 µL. L−1 air for KrS population and 56.29 µL. L−1 air for MhR population). Also, all extracted essential oils were found to be repellent to the adult females of both MhR and KrS populations, with higher repellency effect of S. khuzestanica oil. The effect of the LC20 of the essential oils on detoxifying enzymes including Glutathione S-transferases (GSTs), esterases (ESTs) and cytochrome P450 monooxygenases (P450) was tested against both populations. Significant higher activity of all enzymes was detected in MhR population regardless of essential oils treatment. The activity of GSTs and esterases increased significantly in mites treated with all essential oils, while a tendency for a decrease in P450 activity was detected following essential oils treatment. These results indicate that the essential oils of the all selected plants, especially S. khuzestanica, have a good potential to be used in integrated management programs of T. urticae which is a serious pest in the greenhouses.