Hello Philip,

You have two basic options for removing the undesired grass – Physical removal (dig it out) or chemical removal (apply a herbicide to kill it). Once the grass is removed, you will need to spot-seed or place sod in the area to fill in the bare spots. If you seed, when you choose a seed mixture to reseed, be careful to choose a seed product that has exclusively Kentucky Bluegrass cultivars so you don’t find yourself in the same situation again. By appearance, you irrigate regularly, so you can reseed or sod now. https://www.canr.msu.edu/news/six_steps_to_fall_turfgrass_establishment

If you choose to sod instead of seeding, you can find sod at your “big box” home improvement store. Make sure you call ahead and find out what day they receive sod shipments, because you will want to buy it as fresh as possible.

It is difficult to identify grass species just from a distant photo. The type of grass only matters if it is bent grass or Annual Bluegrass. These varieties can be eradicated by a selective herbicide (Tenacity) without affecting the Kentucky Bluegrass. Any other type of grass plant will need to be killed with a non-selective herbicide. If you apply a non-selective herbicide such as glyphosate, you need to be careful, because it will kill the Kentucky bluegrass along with the undesirable grass. In this case, you will want to completely spray the undesirable grass and limit overspray on the desirable grass.

Since the patches of undesirable grass are large, it is much easier to avoid identification and just use a non-selective herbicide.

Hope this helps.