re: Backyard is infested with torpedo.

Question for the board: We installed a pool last year in July and the contractor left some sand that he used to tamp underneath the fiberglass pool shell. Hurricane Laura hits and the sand gets left in my yard for a period of time. Post storm, he removes the sand pile but now I have torpedo growing where the pile was. I sprayed with Round Up and will likely spray again in a week or so. Tried to get in contained to just that area.

How will I know that I killed all the torpedo? Do I have to till and spray again? How do I prep it for sod. My yard is St Aug.