Comparing impacts of plant extracts and pure allelochemicals and implications for pest control

Many plant extracts or allelochemicals show a broad spectrum of activity against pests and such products have long been touted as attractive alternatives to synthetic chemical pesticides for pest management because they pose little threat to the environment or to human health. The studies available suggest that plant-based materials do affect arthropod pests, vectors and other pathogens, yet only a handful of botanicals are currently used in agriculture in the industrialized world, and there are few prospects for commercial development of new botanical products. Secondary allelochemicals from plants are usually commercialized as single, concentrated compounds, despite research showing that compound mixtures reduce pest resistance better than single compounds. Several factors appear to limit the success of botanicals, most notably regulatory barriers and the availability of competing products of microbial origin and fermentation products that are costeffective and relatively safe compared with their predecessors. In the context of agricultural pest management, botanical pesticides are best suited for use in organic food production in industrialized countries but can play a much greater role in the production and post-harvest protection of food in developing countries. It is in developing countries that are rich in endemic plant biodiversity where these pesticides may ultimately have their greatest impact in future integrated pest management (IPM) programmes, given their safety to non-target organisms and the environment. However, there is a need to organize natural sources, develop quality control, adopt standardization strategies and modify regulatory mechanisms.