A preliminary model for weed control according to thresholds in winter oilseed rape

The specific competition of important weed species including volunteer barley that occur in oilseed winter rape were investigated. By using yield loss/infestation relationships weed economic thresholds for oilseed rape, are proposed preliminarily. "Competition indices" equivalent to the slope of linear regressions describing the relationship between weed density and percent grain yield loss were used to create a preliminary decision model. By multiplying these indices by the weed density of each weed species and summing the products, yield losses in rape caused from a variety of simultaneously occurring weeds can be predicted. Additional correction factors including crop vigor, relative time of weed emergence and expected yield help to adjust the model to individual field situations. This preliminary model was included in a decision that utilizes available strategies of integrated plant protection while emphasizing potential weed control options from preplant incorporated to postemergence treatment