Much of the last half-century of weed science and weed management technology has been directed, implicitly and explicitly, at weed eradication. Is this a realistic possibility in most arable fields, pastures, and rangelands? We believe it is not, given the ecological similarities between weeds and the crops they infest, the dispersal ability of many weed species, and the capacity of most weeds to adapt rapidly to selection pressures imposed upon them (see Chapter 10). Conventional efforts to eradicate weeds with herbicides have reduced weed competition and improved farm labor efficiency, but have also incurred substantial costs, including environmental pollution, threats to human health, and growing dependence on purchased inputs. New approaches are needed to manage weeds effectively while minimizing or eliminating such costs.
This chapter has introduced the concept of weed management systems that are less reliant on herbicides and more reliant on ecological processes, such as resource competition, allelopathy, herbivory, disease, seed and seedling responses to soil disturbance, and succession. We call this concept ecological weed management. Ecological weed management does not exclude the use of herbicides, but minimizes their use through the creation of weed-suppressive agricultural systems. Like conventional management systems, ecological weed management will not eliminate weeds. However, as discussed in later chapters, it has the potential to effectively reduce weed density, limit weed competitive ability, and prevent undesirable shifts in weed community composition, while lowering the use of nonrenewable resources, minimizing threats to human health and the environment, and providing a net benefit to local and national economies.
In contrast to chemically based approaches, ecological weed management has no shortlist of prepackaged, broadly applicable remedies. Instead, it relies on biological information, multiple tactical options, farmer decision-making, and careful adaptation of general design principles to site-specific conditions. Farmers clearly assume a larger burden of responsibility for insuring success when using ecological rather than chemical weed management systems. On the other hand, the benefits of using an ecologically based approach may include more durable weed suppression, cleaner air and water, and less damage to nontarget organisms. Ecological farming may also promote greater farm profits, through cost reductions and price premiums, and healthier rural communities, through practices that are especially well suited to farms that are family-owned and operated.
The development of ecological weed management systems is in its infancy.
As noted in the following chapters, many important research questions remain to be answered. In addition, changes in educational modes and government policies are required if ecological weed management is to be implemented on a broad scale. None the less, we believe that knowledge about ecological weed management and opportunities to apply that knowledge in farm fields are sufficiently advanced to justify increased use and further development of ecological management methods. We hope this book provides the reader with some of the information necessary to proceed.
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