Rumex obtusifolius : its costs and the benefits of control.

The effects of R. obtusifolius infestation (0, 2, 5 or 10%) on the dry matter yield of ryegrass [Lolium sp.] were studied at the Scottish Agricultural College in Scotland in 1999. The results revealed that yield losses increased with the increase in the level of infestation. In an experiment conducted at the Institute of Grassland and Environmental Research in England, the effects of Pastor [clopyralid + fluroxypyr + triclopyr], applied on 30 April 1999 (4 litre/ha) and 13 June 2000 (2 litre/ha), on the dry matter yield of ryegrass under high or low R. obtusifolius density were studied. The application of Pastor increased the dry matter yields by 1.97 and 2.56% in plots with high and low infestation by R. obtusifolius relative to the control (untreated). In addition to the increase in yield, forage treated with Pastor tended to have a slightly higher mean percentage of digestible organic matter in the dry matter (62.27%) compared to the control (61.26%).