Every year around this time we spray the dormant Zoysia turf with a pre and post emergent herbicide. The pre emergent herbicide keeps weeds from growing in it. The post emergent herbicide is glyphosate aka roundup. Because the zoysia is dormant (not green) the glyphosate cannot enter into the plant through photosynthesis. What we are targeting in this spray is mostly annual bluegrass and clover. Those weeds are green and will take in the glyphosate. The blue tint that you see is simply a tracker so we are able to see where we sprayed. The result once temperatures rise is a weed free playing surface.