Council appear to have sprayed a jet of some weed and grass killer
across my lawn when killing the weeds on the footpath. I don't suppose
there's any antidote, particularly now it shows up quite clearly?
Probably happened a couple of weeks ago -- I noticed an area last
week which wasn't very green and watered it. By this week, it's
very clear from the pattern of the dead area exactly what's happened,
a dead spray shaped area with a sharp cutoff caused by the gate post.
Also, it's dying at the same rate as the weeds on the pavement.

--
Andrew Gabriel