Toxic and antifeedant activities of potato glycoalkaloids against Trogoderma granarium (Coleoptera: Dermestidae) Gomah E. Nenaah * Zoology Department, Faculty of Science, Kafrelsheikh University, Egypt article info Article history: Received 4 July 2010 Received in revised form 5 October 2010 Accepted 17 November 2010 Keywords: Glycoalkaloids Potato Bioinsecticides Antifeedants Khapra beetle Trogoderma granarium abstract The total glycoalkaloid fraction (TGA) and the two glycoalkaloids, a-chaconine and a-solanine of potato, Solanum tuberosum, were isolated. Their toxic and antifeedant activities against the Khapra beetle, Trogoderma granarium Everts were investigated. Results indicated considerable toxicity, especially when adults were topically treated with the glycoalkaloids. The TGA fraction was the most toxic with LC 50 ’s of 16.7 and 11.9 mg/mg insect, 48 and 96 h post treatment, respectively. LC 50 ’s of a-chaconine and a-solanine 96 h post treatment were 18.1 and 22.5 mg/mg insect, respectively. Moderate toxicities were recorded when insects were confined on dry-film residues of botanicals with LC 50 ’s ranging between 26.1 and 56.6, and 19.4 and 45.7, mg/cm 2 48 and 96 h post treatment, respectively. Nutritional studies using the flour disc bioassay revealed significant reduction in the growth rate (RGR), food consumption rate (RCR) and food utilization (ECI) by T. granarium at concentrations ranging between 20 and 30 mg g 1 food with feeding deterrent indices reaching 82.4% with the TGA fraction. When tested as binary or crude alkaloidal mixtures, toxic and antifeedant activities of glycoalkaloids were increased, indicating some additive interaction among these botanicals. There is potential for use of such compounds to protect stored grains from insect infestation. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) is considered to be one of the most destructive pests of stored grains and cereal products (Lowe et al., 2000). It has become established in different regions of the world including northern Africa, the Mediterranean region, southern Europe, and the entire continent of Asia. The problem of preventing the beetle’s spread is compounded by its ability to survive for several years in the larval stage with little or no food, and its habit of hiding in cracks and crevices. The control of this insect relies heavily on the use of synthetic insecticides and fumigants. The use of conventional insecticides as a pest control method undoubtedly increases yields and protects stored products, but their excessive or indiscriminate use involves serious health hazards, toxic effects on non-target organisms, direct toxicity to users and increasing costs (Prakash and Rao, 1997; Kim et al., 2003). In response to a growing demand for foodstuffs that are free of pesticide or toxic residues, and because stored-product insects are continuously developing resistance to individual insecticides, the use of such chemicals is becoming increasingly restricted (Arthur, 1994; Donahaye, 2000; Zettler and Arthur, 2000; Kljaji c and Peri c, 2005; Daglish, 2008). These problems have highlighted the need for the development of new types of selective, environmentally acceptable insect control alternatives that have the potential to replace synthetic pesticides and are convenient to use. For these reasons, there is renewed interest in phytochemicals and plant-derived materials to use as pest control agents (Isman, 1995, 2007; Hagstrum and Subramanyam, 1996; Liu et al., 2000; Seffrin et al., 2010). Recently, many plant-derived materials have been investigated as insecticides and growth regulators against insects of stored prod- ucts (Tapondjou et al., 2002; Papachristos and Stamopoulos, 2002; Park et al., 2003; Cox, 2004; Han et al., 2006; Rozman et al., 2007; Cosimi et al., 2009). The leaves and tubers of the cultivated potato, Solanum tuberosum L, contain two naturally occurring toxins, the steroidal glycoalkaloids, a-solanine and a-chaconine (Fig. 1), which comprise over 95% of the total glycoalkaloids present in the potato plant (Mondy and Gosselin, 1988; Percival et al., 1996; Friedman, 2004). These secondary plant metabolites play an important role in the plant’s physiology and defense against pathogens, insects, and other herbivores (Morris and Lee, 1984; Lachman et al., 2001; Friedman, 2006). No reports are available in the literature regarding the efficacy of potato glycoalkaloids against the Khapra * Present address: Department of Biology, College of Arts and Science, Najran University, P.O. Box 1988, Najran, Saudi Arabia. Tel.: þ966 558896216. E-mail address: gnenaah2000@yahoo.com. Contents lists available at ScienceDirect Journal of Stored Products Research journal homepage: www.elsevier.com/locate/jspr 0022-474X/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jspr.2010.11.003 Journal of Stored Products Research 47 (2011) 185e190