Pakistan J. Zool., vol. 46(5), pp. 1407-1414, 2014. Insecticidal Activity of Essential Oils of Four Medicinal Plants Against Different Stored Grain Insect Pests Shahzad Saleem, 1 Mansoor ul Hasan, 1 * Muhammad Sagheer 1 and Shahbaz Talib Sahi 2 1 Department of Entomology, University of Agriculture, Faisalabad, Pakistan 2 Department of Plant Pathology, University of Agriculture, Faisalabad, Pakistan Abstract.- Studies were carried out to investigate the insecticidal activity of essential oils of four locally grown plants such as Datura stramonium, Eucalyptus camaldulensis, Moringa oleifera and Nigella sativa against three major insect pests viz., Tribolium castaneum, Trogoderma granarium and Cryptolestes ferrugineus responsible for economic loss to stored commodities. Test insects were fumigated with concentrations of 5, 10, 15 and 20 µl/L under laboratory conditions at 30±2°C and 65±5% relative humidity. Essential oils fumigation significantly affected the mortality at all levels of concentration and exposure periods. Among essential oils D. stramonium was found to be the most toxic against T. granarium (14.46%) and C. ferrugineus (28.49%) while N. sativa showed the highest fumigant mortality (20.06%) against T. castaneum. Overall results show that C. ferrugineus was found to be the most susceptible test insect with 23.79 % mean mortality followed by T. castaneum (17.11%) and T. granarium (12.27%). Higher mortality was found to be concentration and exposure time dependent. The results demonstrate that the essential oils of investigated plants can be used as fumigant to control insect pests of stored products. Keywords: Plant essential oil, fumigant toxicity, Tribolium castaneum, Trogoderma granarium, Cryptolestes ferrugineus INTRODUCTION After harvesting, approximately 1660 insect species attack the agricultural produce during different phases like transportation, processing, marketing and storage (Hagstrum and Subramanyam, 2009). Losses caused by these insect pests may reach up to 30% during storage (Haubruge et al., 1997). Among these insect pests Tribolium castaneum (Mondal, 1994; Danahaye et al., 2007), Trogoderma granarium (Burges, 2008; Mark et al., 2010) and Cryptolestes ferrugineus (Suresh et al., 2001; Mason, 2003) are documented to be the most damaging and destructive pests of stored products throughout the world. About 2-6% food grain production of Pakistan is lost every year during storage by stored grain insect pests (Avesi, 1983) Synthetic insecticides (pyrethroids and organophosphates) and fumigants (methyl bromide and phosphine) are commonly used to control these insect pests throughout the world. Out of these control strategies, fumigants (because of their broad ______________________________ * Corresponding author: mansoorsahi2000@yahoo.com 0030-9923/2014/0005-1407 $ 8.00/0 Copyright 2014 Zoological Society of Pakistan spectrum action and rapid penetration without residues) are known to be convenient and economical control measure (Mueller, 1990; Varma and Dubey, 2001; Ogendo et al., 2008). Methyl bromide is completely phased out as it was found one of main causes of ozone depletion (Butler and Rodriguez, 1996; Shaaya and Kostyukovsky, 2006; Tayoub et al., 2012). The control of stored product insect pests mainly depends on application of phosphine (Varma and Dubey, 2001). There are also many problems associated with its application, such as adverse effects on non target organisms and environment, human health safety concerns and pest resistance and resurgence (Ogendo et al., 2008). Almost all major pests of stored products have developed resistance against phosphine (Pimentel et al., 2007; Lorini et al., 2007; Nayak et al., 2012). This situation demands a serious effort to find out some safe, viable, biodegradable, environment friendly and effective substitute to these conventional fumigants. Botanicals extracted from higher plants have been found suitable after investigating their fumigant insecticidal properties by many scientists (Isman, 2006, 2008; Rajendran and Sriranjini, 2008; Sagheer et al., 2013). A wide number of plant essential oils and their constituents have been proved for their fumigant insecticidal action against stored product pests (Kim and Ahn,