First and foremost it is necessary to develop a prevention system based on agro-ecological insight. This means that agriculture should seek an ecological approach that makes better use of the buffering and stabilising capacity of the agro-ecosystem itself, in order to help suppress biotic stresses. Vereijken (1997) developed a methodological way of prototyping arable farming systems in interaction with pilot farms that may result in the design of sustainable cropping systems with a strongly reduced use of pesticides.
A logical second approach to the reduction of agronomically and environmentally negative side effects of chemical control is to refine their use by (a) developing better chemicals of which less is needed for effective control and which are less damaging to the environment, and (b) applying them in a technologically more advanced way.
This last aspect of improving application techniques may include making use of precision techniques or using tools to increase the efficacy. A good example is the use of the minimum lethal herbicide dose based on high-tech measurements with chlorophyll fluorescence shortly after application, thus predicting the efficacy of the application. After this system had been tested for two years, most farmers were quite satisfied with the technique and had enough trust in the method actually to apply it (L.A.P. Lotz, Plant Research International, personal communication). This technique can result in a tremendously reduced input of chemicals, but not in a reduction of the dependence of the farm activities on chemical inputs. Although this technological approach of rationalising and refining input of chemicals is an important strategy that should not be ignored or underestimated, it cannot be the only one.
An integrated approach makes use of a wide range of preventive or non-chemical control measures, trying to avoid chemical input and using biocides only where the other tools fail. Agricultural science is working on developing a tool kit that will go a long way in this direction, and will make it increasingly rare for chemicals to be needed. Unpublished research of the former Department of Agronomy of Wageningen University, for example, showed that in a cropping system with a very high frequency of potato cultivation and an intended heavy pressure of a variety of potato pests and diseases, a diversity of non-chemical control measures could make the cropping system healthy again and restore the yield to the level of the treatment with full chemical control. Research is currently also working on risk assessments related to restricted use of chemicals in the conversion to more sustainable arable farming (e.g. de Buck 2001).
The most extreme approach is when a farmer decides to refrain from any use of biocides and accepts the incidental failure of the crop or the incidental high yield and quality losses.
All such approaches require a systems approach in which the farmer makes use of ecological principles at the systems level to prevent, suppress and control biotic stresses. This is partly a return to old principles, but now using new technologies. In no respect can it be considered as a return to old technology. In the past, farmers relied on and actively enhanced the stability of the agro-ecosystem, because they could not control the fluctuations that would otherwise occur. The difference now is that we are currently seeking stability at a much higher level of production, and thus a much larger intensity of use and a higher rate of turnover of resources. We do so on the basis of much more scientific knowledge, while using much more advanced equipment and tools.
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