![]() ![]() Pests may also be transported to countries in which they are not indigenous by the introduction of new crop types or animal breeds, with similar results. ![]() In the absence of their normal natural enemy complex or of environmental constraints these introduced species may become pests and cause extensive damage to crops or livestock. One of the factors influencing the increased introduction of exotic insect species has been the increase in importation of foreign products and materials. Virtual reliance on chemicals leading to an increase in pest problems particularly for insects.Plant breeders, commercial importers, distributors of food aid and general commerce inadvertently introduce pest species. The search for better cultivars and accelerated movement of plant material around the world and with it the movement of pests. ![]() Intensification results in a reduction of intervals between plantings of the same crop, or overlap of crops, which provides a continuous resource to pests.Reductions of natural enemies around crops means that natural enemies of pests must come to the crop from increasingly small and more distant non-crop reservoirs, entering crops too late or in too little numbers to prevent pest outbreaks.Generally, high yielding crop cultivars can provide improved conditions for pest colonization, spread and rapid growth.The concentration of a single plant species/variety in ever larger and more extensive monocultures increases its apparency to pests and the number of pest species which colonize it (Strong et al., 1984).The intensification of agriculture has created new or greater pest problems in a number of ways: The history of pest management is a subset of the history largely of agriculture and while pests have been a chronic problem in agriculture since the beginning, many of today's serious pest problems are the direct consequence of actions taken to improve crop production (Waage, 1993). ![]()
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