Combining cutting and herbicide application for Ambrosia artemisiifolia control
The effect on Ambrosia artemisiifolia (common ragweed) of combining cutting and herbicide application was studied in pot experiments in Germany and Denmark in 2013. Single plants of common ragweed were established in 2 L pots in glasshouses. Two cutting treatments were conducted: cutting to 10 cm height at the beginning of male budding (BBCH 51-59) and no cutting. Clopyralid (in Germany: Lontrel 600, in Denmark: Matrigon), mesotrione (in Germany and Denmark: Callisto) and glyphosate (in Germany: Clinic, in Denmark: Roundup Bio) were applied at 4 doses at three different timings: on the day of cutting, one week and two weeks after cutting. The plants were harvested 5 weeks after the last herbicide application. At both sites clopyralid and mesotrione had a low efficacy on common ragweed when applied on developed plants with only minor differences in efficacy at the three timings. Application after cutting improved the efficacy of clopyralid at both sites and of mesotrione in Denmark. In Germany glyphosate had a higher efficacy on noncut plants in comparison to the cut plants, in Denmark it was vice versa. The highest dose of glyphosate provided higher control levels on developed plants than clopyralid and mesotrione at both sites. In Denmark the highest effects were obtained shortly after cutting with the maximum dose of each herbicide and declined with time between cutting and herbicide application. In summary the results demonstrated that herbicides can be applied shortly after cutting without loss of efficacy.