Minufiya J. Agric. Res. Vol.37 No. 1: 221 - 230 (2012) "http://www.mujar.net" COMPOSITION AND ACARICIDAL ACTIVITIES OF Lavandula officinalis ESSENTIAL OIL AGAINST Tetranychus urticae (ACARI: TETRANYCHIDAE) H. M. M. Heikal (1) , H. K. Abd-Elhady (2) and Nada O. Edrees (3) (1) Economic Entomology & Agricultural Zoology Dept. Faculty of Agric., Minoufiya Univ., Egypt. (2) Department of Pesticides, Faculty of Agriculture, Minoufiya Univ., Shebin El-Kom 32511, Egypt. (3) Department of Biology, Faculty of Sciences for Girls, King Abdulaziz Univ., Jeddah, Kingdom of Saudia Arabia. (Received: Nov. 24, 2011) ABSTRACT: Plant essential oils (EOs) may be an alternative source of materials for two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) control because it constitute a rich source of bioactive chemicals. The EO from aerial parts of lavender Lavandula officinalis were characterized by GC/MS analysis and investigated for its acaricidal activities against the adults of T. urticae under laboratory conditions. The main constituents of the oil were linalool (38.85%), nerol (32.24%), camphor (11.30%) and 1,8- cineole (7.64%). The LC 50 of lavender oil were 24.56, 17.27 and 15.31 ml/L after exposure periods of 24, 48, and 72 hr respectively. The obtain results indicated that the essential oil exhibited a great potential acaricidal effect against two-spotted spider mite at different concentrations that are not phytotoxic to the host plant. Laboratory bioassay results indicated that the essential oil caused high fumigant and repellent activities against T. urticae. The acaricidal observed activity of L. officinalis in this study may be attributed to the major plant constituents. Key words: Lavandula officinalis, Essential oil, Acaricidal activity, Tetranychus urticae, GC/MS analysis, Chemical composition INTRODUCTION Over the past decades, plants EOs were widely used against phytophagous pests and ticks (Iori et al., 2005) and mites (Kim et al., 2004). Aromatic plants are among the most efficient pesticides of botanical origin and essential oils often constitute the bioactive fraction of plant extracts (Cosimi et al., 2009). Among bioactive natural compounds, several plant essential oils (Calmasur et al., 2006) were evaluated as acaricides. Moreover, essential oils have a broad spectrum on insect and mite activity due to their several modes of action, including repellent and antifeedant activities, inhibition of moulting and respiration and reduction in growth and fecundity (Enan, 2001; Akhtar and Isman, 2004). Beside native wild species, several medicinal plants are cultivated in Egypt such as Lavandula officinalis, it is belong to family Lamiaceae, and it is also known as common or English lavender, native to the western Mediterranean region (Chevallier, 1996). Lavender EO has several medicinal properties and biological activities (Bown, 1995). Its powerful antiseptic properties are able to kill many common microorganisms; it also has antiviral properties and is a powerful antidote to some snake venoms (Phillips and Foy, 1990). The oils are generally composed of complex mixtures of monoterpenes, biogenetically related phenols, and sesquiterpenes. Natural products have been used as templates for semi-synthetic acaricidal agents (Tsukamoto et al., 1997a, b). The two- spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most serious pests in some of agricultural systems (Deligeorgidis et al., 2006, 2007). It ingests leaf cell contents, thus reduces plant photosynthesis (Park and Lee, 2002) and potentially decreases yield quality and quantity (Flaherty and Wilson, 1999). These pests are commonly