Killing established St. Augustine grass
 

Greetings! St. Augustine grass has invaded my gardenfrom my
neighbour's garden. I have made a strip of nine inch wide between my
garden and my neighbour by killing everything by spraying ROUNDUP. Now
I can watch any St. Augustine grass crossing into my gardenand remove
them. Now the problem is how to remove the St. Augustine grass which
have already established in my garden. At present I am removing them
manually by pulling each roots. Is there any shortcuts? I use a rake
to get to the roots. Is there any special chemical to kill only St.
Augustine grass? With thanks.