natural-products-in-plant-pest-management

Natural Products from Plants 43an established fact that the use of synthetic chemical pesticides providesmany benefits to crop producers. These benefits include higher crop yields,improved crop quality and increased food production for an ever increasingworld population. Despite this, synthetic pesticides may pose some hazardsto the environment, especially when improperly used by farmers in developingcountries who lack the technical skill of handling them, and who fail toadapt to this technology easily. This may result in undesirable residues left infood, water and the environment, toxicity to humans and animals, contaminationof soils and groundwater and may lead to the development of croppest populations that are resistant to treatment with agrochemicals.Moreover, in Africa and the Near East obsolete pesticides have become asource of great environmental concern. Some stocks are more than 30 yearsold and are kept in poor conditions because of inadequate storage facilitiesand lack of staff trained in storage management. The Food Agricultural Organization(FAO) estimated that developing countries are holding stocks ofmore than 100,000 tonnes of obsolete pesticides, of which 20,000 tonnes are inAfrica. Many of these chemicals are so toxic that a few grams could poisonthousands of people or contaminate a large area. Most of these pesticideswere left over from pesticide donations provided by foreign aid programmes.In the absence of environmentally sound disposal facilities, stocks are constantlyincreasing (Alemayehu, 1996). Obsolete pesticide stocks are, therefore,potential time bombs. Leakage, seepage and various accidents relatedto pesticides are quite common and widespread. Storage conditions rarelymeet internationally accepted standards. Many pesticide containers deteriorateand leak their contents into the soil, contaminating groundwater and theenvironment. Most stores are in the centres of urban areas or close to publicdwellings. According to the World Health Organization (WHO) there are 25million cases of acute occupational pesticide poisoning in developingcountries each year (Alemayehu, 1996).As a result of the problems outlined above, farmers in developing countriesand researchers alike are seeking less hazardous and cheaper alternatives toconventional synthetic pesticides. One such alternative is the use of naturalproducts from plants to control plant diseases in crops as part of an organicapproach to Integrated Pest Management (IPM) programmes. Justification forpursuing this alternative can be found in the following statement published adecade ago by the Environmental Protection Agency (EPA) regarding theadvantages of natural products from plants in the control of plant diseases:Natural products from plants have a narrow target range and highly-specificmode of action; show limited field persistence; have a shorter shelf life andpresent no residual threats. They are often used as part of Integrated PestManagement (IPM) programmes; are generally safer to humans and theenvironment than conventional synthetic chemical pesticides and can easily beadopted by farmers in developing countries who traditionally use plant extractsfor the treatment of human diseases. (Deer, 1999)A further reason for exploring the use of plant extracts or natural productsas biological pesticides more extensively can be found in the plant