natural-products-in-plant-pest-management

Global Scenario and Natural Products 5(a) (b) (c)CHH 3C CH 2HOHOOHOOHOOHHONOHNNCH 3OCH 3HOHOOHOOOHOHFig. 1.1. (a) Rotenone (b) Nicotine (c) Ryanodine.Used widely until the 1940s, such botanical pesticides were partly displacedby synthetic pesticides that at the time seemed easier to handle andlonger lasting. With the knowledge of the adverse effects of synthetic pesticides,worldwide attention is currently being given to shifting to nonsyntheticsafer pesticides. There is renewed interest in the application ofbotanical pesticides for crop protection, and scientists are now experimentingand working to protect crops from pest infestations using indigenousplant materials (Roy et al., 2005).1.4 Plant Products in Current Worldwide Use as PesticidesThe plant kingdom is recognized as the most efficient producer of chemicalcompounds, synthesizing many products that are used in defence againstdifferent pests (Prakash and Rao, 1986; 1997; Charleston et al., 2004; Ismanand Akhtar, 2007). Higher plants contain a wide spectrum of secondarymetabolites such as phenolics, flavonoids, quinones, tannins, essential oils,alkaloids, saponins and sterols. Tens of thousands of secondary products ofplants have been identified and there are estimates that hundreds of thousandsof such compounds exist. These secondary compounds represent alarge reservoir of chemical structures with biological activity. Therefore,higher plants can be exploited for the discovery of new bioactive productsthat could serve as lead compounds in pesticide development because oftheir novel modes-of-action (Philogene et al., 2005). The rainforest plantsare particularly thought to have developed a complete array of defenceprovidingchemicals. This resource is largely untapped for use as pesticides(Tripathi et al., 2004).Extracts prepared from different plants have been reported from time totime to have a variety of properties including insecticidal activity, repellenceto pests, antifeedant effects, insect growth regulation, toxicity to nematodes,mites and other agricultural pests, and also antifungal, antiviral andantibacterial properties against pathogens (Prakash and Rao, 1986, 1997).