Here are a couple of pictures of our Roundup trials from last fall. As you can see there is some thinning to the turf, but this strip is greener than the rest of the fairway around it. So why is that? The green turf left unscathed is the bluegrass that we want. The dead stuff is ryegrass and poa, but why is that strip greener? The bluegrass does green up quicker in the early spring and also the reduction in competition allows it to get whatever little bit of nitrogen fertility available now without having to share it (with the dead ryegrass). Basically lower number of plants in that square vying for that same amount of fertility so it appears slightly greener. Interestingly though the bluegrass greens up quicker now, but the ryegrass will strongly outgrow the bluegrass in the next month.
Read about what we have done with these test strips and what we were hoping to accomplish in this previous post. https://whgcturf.blogspot.com/2017/06/poa-control.html
So what have we figured out with this experiment over two years time? Unfortunately it has not been as effective in eliminating poa annua as we had hoped. Timing of the application is critical and there seems to be a window in the mid-September to mid-October period that seems to be most effective. As we have increased rates the effectiveness increases but it also becomes too damaging to the ryegrass and bluegrass. So while it hasn't been a total success it has shown some promise and we may still utilize this cheap alternative to poa control in certain situations.