Medium-term consequences of enhanced weed-thresholds in cereals on weed infestation in the succeeding crops

Changing economic backgrounds could lead to higher damage thresholds for we eds in cereals. To investigate the consequences in terms of increasing weed iness due to applying these thresholds, field experiments were conducted on four sites for five years. The tested thresholds yielded in accelerated we ed density in the succeeding crops but did not lead to higher costs for con trol measures compared to routine treatments. Weed infestation was governed by the seed input as well as by the crop grown and the year. Herbicide sav ings with the new threshold were limited because only at one site the weed density ranged between the old and the new threshold level. Higher weed thr esholds are acceptable only in high-input cropping systems because weed com petition increased and wheat market quality decreased in low-input systems.