Thistles and ragwort can be controlled in species-rich grassland

UK - June 22, 2012

Noxious grassland weeds such as creeping thistle (Cirsium arvense) and common ragwort (Senecio jacobaea) can be controlled in valuable, bio-diverse meadows without harming the desirable plants, according to David Roberts, agronomist with herbicide company Dow AgroSciences.
 
Mr Roberts was presenting the results of a trial carried out at three UK sites last year, at the ‘Restoring Diverse Grassland’ conference held in Oxford this week, organised by the Association of Applied Biologists.  
 
“Re-establishing botanically-rich grassland can be difficult, especially in the early stages, when the fertile soil encourages perennial weeds like docks and thistles,” said Mr Roberts.
 
“An overall spray of a grassland herbicide such as Pastor will give the best level of weed control in a normal agricultural sward, but could take out desirable species if used on bio-diverse meadows.  
 
“This trial shows that applications of Forefront T made through a weedwiper – which applies herbicide only to plants growing above the main wildflower canopy, is a viable option in this type of situation.”
 
Limited choice
Relatively few herbicides suitable for controlling common ragwort and creeping thistle in grassland have approval, either on-label or off-label for application via weedwipers.
 
Those that do, such as Grazon 90, are not particularly good at controlling ragwort. The development of products containing aminopyralid, allow this weed to be controlled at levels not previously possible.
 
In the trials, the best treatment was Forefront T (5% v/v) when assessed 56 days after applications made at the beginning of June. There was 72.9% control of creeping thistle and 75.5% control of common ragwort. This exceeded the level of control provided by Grazon 90, the industry standard at 56.7% and 55.6% respectively. The two types of weedwiper used – a Logic contra-rotating brush and Micron wetted carpet system performed equally well.
 
“The trials proved that land managers do not have to put up with unsightly weeds in their beautiful meadows,” said Mr Roberts. “Controlling them early will also reduce their ability to spread by seed.”
 
“While Forefront T does not have approval yet for application through a weed wiper, an Extension of Authorisation has been applied for, which, once granted will allow its use to help restore valuable bio-diverse grasslands.”