Repellent activity of essential oils from two species of Citrus against Tetranychus urticae in the laboratory and greenhouse Claudio A.G. da Camara a, b , Yasmin Akhtar b , Murray B. Isman b, * , Rita C. Seffrin b , Fl  avia S. Born a a Programa de P os-graduaç~ ao em Entomologia Agricola, Departamento de Agronomia, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros, s/n, 52.171-900 Recife, PE, Brazil b Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada article info Article history: Received 15 February 2015 Received in revised form 22 April 2015 Accepted 24 April 2015 Available online Keywords: Repellent Citrus essential oil Tetranychus urticae Greenhouse abstract Essential oils from fruit skins of laranja pera (Citrus sinensis Osbeck var. pera) and laranja lima (Citrus aurantium L.) obtained through water distillation were analyzed by GC-FID and GC-MS and their repellence to the twospotted spider mite, Tetranychus urticae Koch, on string was evaluated in laboratory bioassays and greenhouse experiments. Twenty-seven compounds were identified, representing 98.1% and 98.9% of the total constituents of the C. aurantium and C. sinensis var. pera oils, respectively. d- Limonene was the main constituent found in both Citrus species. Both of the natural oils and an artificial mixture of mono- and sesquiterpenes intended to mimic one of the oils showed repellent effects comparable to eugenol (a positive control) for up to 3 h in laboratory bioassays. Both major and minor constituents of the two oils were responsible for the repellent effect. Although both oils showed similar repellent effects, lima oil prevented the movement of mites between plants across oil-treated strings for one week. Lima oil has potential for development as a commercial repellent against spider mites and could prevent their spread in commercial greenhouses. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The two-spotted spider mite (Tetranychus urticae Koch) is a major agricultural pest worldwide (Flamini, 2006). Among the 1200 known species of spider mites, T. urticae is the most polyph- agous and has been reported feeding on at least 150 host plants of economic value. T. urticae occurs in tropical and temperate regions and is found in both greenhouses and in the field. Greenhouse vegetables are a high value crop and even moderate crop damage results in serious economic losses. The same greenhouse produc- tion systems and environmental conditions that are favorable to plant growth and yield are also favorable to the growth and reproduction of diseases and arthropod pests. The control of spider mites is a challenge due to their short life cycle and potentially explosive populations (Saito, 1985). Spider mites can use silken threads as a means of dispersing to other leaves or plants, however adult mites also migrate along the strings employed to secure and support vegetable plants in a greenhouse, such as tomatoes and sweet peppers. A number of different approaches to integrated pest manage- ment using natural plant-based products have been proposed in recent years. Plant material (powdered foliage or rhizomes), crude or semi-refined aqueous/organic extracts and essential oils from certain plants are toxic to various types of arthropods. Essential oils, in particular, demonstrate a wide array of bioactivities in arthro- pods, such as toxicity, oviposition deterrence, antifeedant action as well as both general attraction and repellence (Isman, 2006). In the past 40 years, there has been considerable interest in behavioral manipulation of insects as an alternative to broad- spectrum insecticides for crop protection. In addition to the direct toxic effects of essential oils on insects through contact, ingestion or fumigation, essential oils or their chemical constituents have potentially important behavioral effects on pests, especially as de- terrents and repellents (Akhtar et al., 2010). To avoid the dispersal of mites along strings used to secure plants in a greenhouse, the repellent activity of oils from the fruit peels of two species of Citrus (Citrus sinensis Osbeck and Citrus aurantium L.; pera and lima orange, respectively) grown in * Corresponding author. E-mail address: murray.isman@ubc.ca (M.B. Isman). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro http://dx.doi.org/10.1016/j.cropro.2015.04.014 0261-2194/© 2015 Elsevier Ltd. All rights reserved. Crop Protection 74 (2015) 110e115