natural-products-in-plant-pest-management

Global Scenario and Natural Products 3almost 3000 g/hectare. Unfortunately, there are reports that these compoundspossess inherent toxicities that endanger the health of the farm operators,consumers and the environment (Cutler and Cutler, 1999). Pesticides aregenerally persistent in nature. Upon entering the food chain they destroy themicrobial diversity and cause ecological imbalance. Their indiscriminate usehas resulted in the development of a resistance problem among insects toinsecticides, pesticide residue hazards, upsetting the balance of nature and aresurgence of treated populations. Insect resistance to phosphine is a matterof serious concern (Rajendran, 2001; Benhalima et al., 2004; Thie and Mills,2005; Dubey et al., 2008). The repeated use of certain chemical fungicides inpacking houses has led to the appearance of fungicide-resistant populationsof storage pathogens (Brent and Hollomon, 1998). The ability of some ofthese pests to develop resistance curbs the effectiveness of many commercialchemicals. Resistance has accelerated in many insect species and it wasreported by the World Resources Institute that more than 500 insect and mitespecies are immune to one or more insecticides (WRI, 1994). Similarly about150 plant pathogens such as fungi and bacteria are now shielded againstfungicides (Shetty and Sabitha, 2009). Moreover, the control of such pests hasbecome increasingly difficult because of reduced effectiveness of pesticidescaused by the emergence of pesticidal resistance in arthropod pests.Reliance on synthetic chemicals to control pests has also given rise to thedestruction of beneficial non-target organisms (parasitoids and predators),thereby affecting the food chain and impacting on biological diversity. Therehave also been cases of pests becoming tolerant to insecticides, resulting inthe use of double and triple application rates (Stoll, 2000).Furthermore, the use of synthetic chemicals has also been restrictedbecause of their carcinogenicity, teratogenicity, high and acute residualtoxicity, ability to create hormonal imbalance, spermatotoxicity, long degradationperiod, environmental pollution and their adverse effects on foodand side effects on humans (Omura, et al., 1995; Unnikrishnan and Nath,2002; Xavier, et al., 2004; Konstantinou, et al., 2006; Feng and Zheng, 2007).Pesticides can be remarkably persistent in biological systems. They havebeen reported to be accumulated in ecosystems. Osprey eggs in the QueenCharlotte Islands, polar bear fat in the high Arctic, and the blubber of whalesin all the oceans of the world are contaminated with pesticide residues, eventhough all these creatures live far from point sources of pesticide application(CAPE, 2009). Water and wind, as well as the bodies of animals that serveas prey for others (including humans) higher on the food chain, are theuniversal vectors for pesticide dispersal. Highest on the food chain, humanbreast milk contamination is of great concern because of high levels ofbio-accumulated pesticides. The World Health Organization (WHO) estimatesthat 200,000 people are killed worldwide, every year, as a direct resultof pesticide poisoning (CAPE, 2009). Pest control strategies, therefore, needproper regulation in the interest of human health and environment. In recentyears there has been considerable pressure on consumers to reduce or eliminatechemical fungicides in foods. There is increasing public concern over thelevel of pesticide residues in food. This concern has encouraged researchers