Competitive effects of volunteer oilseed rape in wheat depending on the weed density

Weeds are a major factor for yield losses in crop production. They compete with the crop for limiting factors such as space, nutrients, water and light. Crop plants themselves can occur as weeds in crop rotations (e.g. oilseed rape). In general, volunteer oilseed rape in cereals is successfully controlled by acetolactate synthase (ALS) inhibitors. When growing Clearfield® oilseed rape, the control of volunteer oilseed rape plants must be adjusted towards their ALS-tolerance. In the present study, the influence of different oilseed rape densities on yield and quality parameters of spring- and winter wheat was investigated. Significant negative correlations were detected for the parameters heads/m2, hectoliter weight and yield. The moisture content and the dockage were subjected to a positive correlation. Based on a non-linear regression analysis, even an infestation with one volunteer plant/m2 resulted in a possible yield loss of 0.74 to 1.61 %. We conclude that an adjustment of the herbicide regime along with good farmers’ practice (harvest date of oilseed rape, harvest technique, mechanical volunteer control, crop rotation) result in a successful volunteer control. Oilseed rape volunteers in general and Imidazolinone-tolerant volunteers in special will have no relevant impact on yield of subsequent cereals accordingly.