A customer asked us to identify the weed in the photo with recommendations for controlling it.

It’s umbrella sedge (Cyperus eragrostis).  

Best control is by glyphosate, which means selective control in pasture is not possible as far as we know, because the things that won’t kill grasses, won’t kill umbrella sedge … sedges being grass-like species.  GrassMate, MCPA, 2,4-D therefore are not effective.  MSF600 would probably work ok but that will damage the grass as well.

So, if it’s in a situation where grass damage isn’t an issue, use Glyphosate 360, Glyphosate 540 or Granny where you should get reasonable results when it is smaller.  After that point in its growth, control can be erratic because it becomes difficult for the herbicide to fully translocate through to the mature underground tuberous root system.  I know that people controlling it in ornamental turf have to spot spray it with glyphosate 3-4 times in a growing season to get thorough control.  It will also be best to include SuperWetter penetrant in the mix at 0.1-0.2%.