Control of Weeds and Other Biotic Factors

Weeds are plants whose presence is undesirable at a time and/or place because they compete with crops for resources, deteriorate the quality of the harvested product, and can hinder harvesting. The most important weed species include C4 perennials with vegetative propagation. Usually, weeds can produce many seeds that often present dormancy, which generates a soil seed bank that germinates over many years. This prevents weed eradication and forces us to use control techniques to keep tolerable weed populations. Weeds adapt in a few years to the cropping system, in special to control methods. Control techniques include herbicides and cultural practices such as tillage, mulching, mowing, and crop rotation. Crop management has an important effect on the incidence of pests. The irrigation method and frequency determine the germination of weeds and influence the infection by aerial or soil pathogens. Biological control is effective with invasive weeds and some insects. The ability of weeds to evolve in response to the selection pressure exerted by control measures forces us to establish long-term strategies (weed management) which should be based on detailed knowledge of the ecology of the weed species. Then different types of control should be alternated to improve the control efficiency.