re: Paging Grass Gurus - What’s going on with my St. Aug?

I recently (early July) had what looks like the same issue in my newly planted St Aug. I reached out to the LSU Ag Center and was told it was tropical sod web worms--they did a number on my lawn (actually quite a bit worse than yours). Based on your pics, I believe you have the same problem. I noticed in one of your pics (the one with your thumb) that there is a white residue on your thumb and on the grass--I was told this frass (excrements from the larvae).

I did two applications of granular bifenthrin and have not seen any new damage. Hoping I caught it early enough for my lawn to recover.