natural-products-in-plant-pest-management

Natural Products from Plants 45a plant (Salisbury and Ross, 1992). If the compound is produced within theplant it is called a plant hormone e.g. auxins, gibberellins, cytokines, abscissicacid and ethylene. Two decades ago, Roberts and Hooley (1988) stated thatthe potential exists to apply a plant extract as a foliar spray in order to stimulategrowth in crop plants and hence increase yields. According to the authors,a principal objective of the agricultural and horticultural industries is tomanipulate plant growth and development in such a way that the quantityor quality of a crop is increased. After the late-1980s an elevated interestdeveloped in terms of identifying natural plant compounds that possess thepotential to manipulate plant growth and development over a short period,e.g. a growing season.From a crop production perspective, the term ‘integrated pest management’,in the broad sense of the word, means to apply more than one methodor product in order to control ‘pests’ that farmers have to deal with on aregular basis. The term ‘pests’, in the broad sense of the word, includes,among other things, insect and weed pests as well as viral, bacterial andfungal diseases. However, the term ‘integrated pest management’ has a differentmeaning when applied in either conventional cropping systems ororganic agriculture. Pest control in conventional cropping systems is mostlydriven by the large-scale use of many different synthetic chemicals and itcannot be denied that great success has been achieved in this way. Due toconsumer resistance and pressure generated by the ‘green revolution’towards the use of synthetic chemicals, a shift towards organic agriculturewas inevitable. Restrictions in terms of synthetic chemical application inorganic agriculture have, in turn, forced a shift towards the use of natural ororganic products.In conventional cropping systems integrated pest management is ratherstraightforward and entails the use of any registered product on the marketthat a farmer might choose, and this applies for any of the ‘pests’ mentionedearlier. The methods of application of these products are in many cases similar,e.g. foliar application, but might include integrated seed, soil and foliartreatments. IPM in organic agriculture is much more complex and controlledand may include sowing multiple crops, extended rotation cycles, mulching,specific soil cultivation methods (Dayan et al., 2009) and the use of organicallycertified natural products.Be that as it may, the reduction in the number of synthetic products as aresult of more stringent pesticide registration procedures (Dayan et al., 2009),such as the Food Quality Protection Act of 1996 in the United States, hasopened the door for the vigorous pursuit of natural products from plantsover the past two decades. In the meantime, many natural compounds fromwild plants have been isolated, purified, identified and patented but, only afew products are commercially available.In this chapter attention will be given to the integrated pest managementconcept, the rationale for considering natural compounds from plants andtheir potential to be applied as agrochemicals in an IPM system in the agriculturalindustry as well as selected areas where some progress have beenmade over the past three decades. In terms of the latter these will include