I live in the northeast and just had new grass seed put down early spring. The first one pulls out easily when it has matured, but when it’s small it grows between the lawn and is hard to pull out. It is literally taking over half of my lawn. Weed and feed has not worked.
I wish I knew myself. It is taking over my lawn. The worst part about it is that in the fall it dies, leaving bare spots where it crowded out the grass.
*** I stumbled on the answer a few minutes ago. It is Japanese Stiltgrass! An invasive weed that will take over your lawn. The good news is you can kill it with the following two produdcts: Acclaim Extra and Bayer Crabgrass Killer for Lawns. I am getting some as soon as I can get to the store. Lowes, home Depot and Walmart carry the Bayer You can read about it here: https://njaes.rutgers.edu/fs1237/