Samenvatting

Triticum aestivum (wheat) is the second most produced crop in the world and is even the most produced crop in Europe. However, in Europe there are many laws controlling the herbicide use and approvals. An important directive that appeared in 1991 led to a significant reduction in the number of herbicides allowed. In addition to this, herbicide-resistant weeds have appeared since 1975. This problem, combined with the reduction in the number of authorized herbicides, means that today the management of weeds, particularly resistant weeds, has become more and more complex. The combination of different herbicides seems to be a good option for controlling weeds, especially those that are resistant. To help farmers respond to this problem, an agrochemical company wanted to evaluate a set of different combinations of herbicides. The purpose was to analyse the efficacy of the different herbicide combinations on a resistant weed (Alopecurus myosuroides) and a non-resistant weed (Viola arvensis). To answer this question, a trial was set up and the following questions were formulated: Main question To what extent do combinations of post emergence herbicides provide improved weed control in winter wheat? Sub questions 1 : How do combinations of post emergence herbicides perform against Alopecurus myosuroides (black grass)? 2 : How do combinations of post emergence herbicides perform against Viola arvensis (field pansy)? 3 : Are all of these herbicide combinations crop safe? 4 : How cost effective are these combinations of herbicides from a farmer’s perspective? After analysis of the results it was found that some combinations had very good weed control results with 94% and 100% but also had a negative effect on wheat. Moreover, after economic analysis in some cases, the theoretical possible yield increases through the use of a product combination did not cover product costs which is 80€ higher. However, other combinations have interesting results and are economically viable. Following these analyses it is recommended that before using combinations, some criteria are essential to take into account such as the weed population in order to be able to estimate the profitability of these products. It is also necessary to select the combinations according to the population and the type of population of weeds present in the field. From a global point of view to avoid the persistence or appearance of new resistances, a rotation of the different modes of action must be done every year.