enemies, which in turn do not find the necessary environmental resources and opportunities in monocultures to effectively suppress pests. As long as the structure of monocultures is maintained as the structural base of agricultural systems, pest problems will continue to persist. Thus, the major challenge for those advocating ecologically based pest management (EBPM) is to find strategies to overcome the ecological limits imposed by monocultures.
Integrated pest management (IPM) approaches have not addressed the ecological causes of the environmental problems in modern agriculture. There still prevails a narrow view that specific causes affect productivity, and overcoming the limiting factor (e.g., insect pest) via new technologies continues to be the main goal. In many IPM projects the main focus has been to substitute less noxious inputs for the agrochemicals that are blamed for so many of the problems associated with conventional agriculture. Emphasis is now placed on purchased biological inputs such as Bacillus thuringiensis, a microbial pesticide that is now widely applied in place of chemical insecticide. This type of technology pertains to a dominant technical approach called input substitution. The thrust is highly technological, characterized by a limiting factor mentality that has driven conventional agricultural research in the past. Agronomists and other agricultural scientists have for generations been taught the “law of the minimum ” as a central dogma. According to this dogma, at any given moment there is a single factor limiting yield increases, and that factor can be overcome with an appropriate external input. Once one limiting factor has been surpassed—for example nitrogen deficiency, with urea as the correct input—then yields may rise until another factor, pests for example, becomes the new limiting factor due to increased levels of free nitrogen in the foliage that attracts and supports the herbivore populations. That factor then requires another input— a pesticide in this case—and so on, perpetuating a process of treating symptoms rather than dealing with the real causes that evoked the ecological imbalance.
The addition of biotechnology-based approaches in pest management is merely a new tool to be used as input substitutions to address the problems (e.g., pesticide resistance, pollution, soil degradation) caused by previous agrochemical technologies. Transgenic crops developed for pest control closely follow the paradigm of using a single control mechanism (a pesticide) that, as a strategy, has been shown to fail repeatedly over time against pest insects, pathogens, and weeds. Transgenic crops are likely to increase the use of pesticides and to accelerate the evolution of “super weeds” and resistant insect pests.
The “one gene–one pest” approach emphasized by plant breeders introducing vertical resistance or by biotechnologists developing transgenic crops has proven to be easily overcome by pests that are continuously adapting to new situations and evolving detoxification mechanisms. There are many unanswered ecological questions regarding the impact of the release of transgenic plants and microorganisms into the environment. Among the major environmental risks associated with genetically engineered plants are the unintended transfer to plant relatives of the “transgenes ” and the unpredictable ecological effects.