| Abstract: | The assessment of economic thresholds of weeds is difficult because there are so many interactions between the various species and the crop. In addition, a precise forecasting of the weather is needed when pre-emergence treatments are performed since the conditions prevailing at that moment will be decisive for the abundance of weeds. Still, there are various possibilities to assess the crop losses resulting from weed competition and attention is drawn to the following two approaches: 1) Long-term assessment in relation to the total weed population in a region, and 2) Competition studies between individual weed species and crop plants in pots or in field experiments. The advantages and disadvantages of the various methods are discussed and the data obtained critically evaluated. It appears that the application of average values to a special situation remains for the moment highly uncertain. |
