Evaluation of five essential oils as botanical acaricides against the strawberry spider mite Tetranychus turkestani Ugarov and Nikolskii

The strawberry spider mite, Tetranychus turkestani Ugarov and Nikolskii (Acari: Tetranychidae), is a serious pest of agroecosystems in southwestern Iran and some other tropical regions. Records show that it has developed resistance to some chemical acaricides. In this study, the chemical composition of five Lamiaceae plant essential oils was examined, and their activity against T turkestani was evaluated. The essential oil composition of savory (Satureja hortensis L.), penny royal (Menthe pulegium L), spearmint (Mentha viridis L), rosemary (Rosemarinus officinalis L), and a thyme-like plant (Zataria multiflora Bioss) was analyzed by GC -MS and fumigant bioassays were performed to determine their acaricidal activity. The results showed that all the essential oils have acaricidal activity at all the tested concentrations. The calculated LC50 values were 5.5, 9.4, 14.5, 15.3, and 29.8 mu l l(-1) air for Z multiflora, S. hortensis, M. pulegium, M. viridis, and R officinalis, respectively. These results showed that Z. multiflora and S. hortensis essential oils, with carvacrol, thymol, and gamma-terpinene as their main compounds, were the most effective oils. In another experiment designed to find the effects of exposure time on the mortality of T. turkestani females, nearly all females died in 20 mu l l(-1) of all the essential oils after 24 h, except in the case of R. officinalis oil, which caused 90% mortality in mites. This study demonstrated that all the tested essential oils have the ability to control T. turkestani and could be useful in the development of new agents for mite control. (C) 2014 Elsevier Ltd. All rights reserved.