Ranunculus acris control in dairy pasture – a comparison of herbicides, plant growth promoters, a bioherbicide and pregraze mowing

The efficacy of control tactics for Ranunculus acris was quantified on poorly- and well-drained soils in a factorial experiment conducted over three years in 18 dairy pastures. Soil drainage, gibberellic acid and nitrogenous fertiliser (growth promoters), and a bioherbicide utilising Sclerotinia sclerotiorum had no effect on the cover of R. acris. The herbicides aminopyralid and aminopyralid+triclopyr, by contrast, gave long-lasting reductions in the cover of the weed and substantial temporary reductions in the clovers. Flumetsulam, thifensulfuron methyl, MCPA, MCPB and MCPB+bentazone were less effective overall. Pregraze mowing reduced R. acris as the frequency of mowing increased. For all herbicides, there was a 1:1 replacement of R. acris by grasses and clovers. The efficacy of the treatments varied greatly between pastures, possibly due to genetic differences between the R. acris populations and their historical exposure to the herbicides.