I have a lawn seeded with "Pennsylvania State Mix" which is Perennial Ryegrass, Kentucky Bluegrass, and Fine Fescue. Will Certainty Herbicide work on this or will it give me bare spots? If it gives bare spots then wouldn't Round-up work better (and cheaper)????? I am so stressed about this--I hope that what I am seeing is Poa Trivialis. I hope this is not just a fungus that could be cleared up easier. The pictures that I have seen are not very clear. The patches that I am experiencing are getting numerous. They are yellowish-green and the grass seems to be matted down. After I mow, I can run my hands through the patches and there is tall grass that was never touched by the mower. Does this seem like Poa Trivialis???