AFBI Trial: Weed-wiper - a very effective tool for rush control
Soft rush is a highly invasive plant, quickly covering grass fields, especially where drainage is poor and where control has been relaxed. Weed-wiping is potentially a very effective method of control and is a technique, whereby a horizontal wick, soaked in systemic glyphosate herbicide, is dragged through a field, by tractor or all-terrain vehicle, at a height which makes contact with the taller-growing rushes, but not lower-growing grasses or broad-leaved plants. The herbicide is taken up by the rushes which are quickly killed.
Rush control trial in Fermanagh, showing the effectiveness of weed-wiping
For a number of years, the Agri-Food and Biosciences Institute (AFBI) has been carrying out trials in Fermanagh investigating the effectiveness of weed-wiping compared with cutting or no treatments on fields of rough grazing. The following treatments were compared: weed wiping or cutting in mid-May; weed-wiping in mid-May followed by cutting in mid-July; cutting in mid-May followed by weed-wiping in mid-July; and an untreated control.
After the first year there was a general reduction in the percentage of ground covered by soft rush with all treatments involving the weed wiper and their effectiveness improved with time. Cutting alone, although reducing rush cover in a particular season, had no lasting effect.
Concern has sometimes been expressed that using a weed-wiper would decrease plant species diversity. There was no evidence for this in the trials. Indeed, the total number of species was consistently higher with all treatments, in particular, combined cutting and wiping treatments, although there was no evidence of a continuing increase over the three years of the trial. Moss cover, however, did increase consistently with all treatments, especially the more rigorous ones, such as combined cutting and wiping, where the weed-wiper boom had to be lowered to make contact with new rush growth, thus tending to take out more of the high-growing plants and contributing to more bare patches and subsequent ingress of moss.
Grass field with high level of plant diversity
Concern has also been expressed that removal of rushes would make the ground very soft underfoot, but the use of soil-penetration probes throughout the trial did not provide any evidence for this. Indeed, if anything, rush removal by whatever treatment tended to increase the resistance of soil to pentration.
Use of the weed wiper in mid-May proved a very effective method of keeping rushes under control and was superior to cutting. Plant diversity was not adversely affected, although it is probably better to use a single weed-wiping treatment than combine it with cutting as this tended to increase the amount of moss and was not generally any better than wiping alone.
From 2006 to 2009, weed-wiper treatments almost completely removed soft rush cover
NB. In Agri Environment Schemes only semi-improved grassland can be wiped or cut in May. And participants in such schemes should refer to their agreements to ensure compliance.
Peter Mercer, Julie Morgan and Mel Flexen, Plant Health and Biodiversity Branch, AFBI