Asked October 29, 2018, 3:58 PM EDT
Sussex County Delaware
From your picture I would identify this as wire grass. This is the curse of lawn owners. It spreads by seed, branches and rhizomes as you know. It is very difficult to eliminate. Older methods involved digging it up which was very difficult and not very effective or using a product like Roundup which took more than one application and of course killed all vegetation as well as only doing a fair job of eliminating the wire grass. At this time of year after a heavy frost the grass above ground will turn brown and seem dead so spraying in not effective. However the plants will emerge from the rhizomes and seeds in full force next spring. A pre-emergent treatment in early spring will prevent the seed from germinating but the grass will spring up from the rhizomes underground. At that time a post emergence treatment as discussed below can be used.
For the post emergent wire grass BioAdvanced (Formerly Bayer Advanced) makes a product called Bermudagrass Control for Lawns. There may be some temporary damage to the lawn grass but it will recover. Be sure to read the label and follow the directions. It may take more than one application. The following link has more information and other products.
Good luck with the lawn.