Have a look at this thread from a few months back. Pay particular attention to the information on Page 3.
http://www.outdoorsmenforum.ca/showthread.php?t=399075
If you need to treat a large area, the commercial product will be more cost effective. If you can buy it directly.
For a mid size residential yard, buy the concentrated Killex and increase the mix ratio to get close to the agricultural/commercial ratio. At that concentration, make sure you apply it properly; don't overspray an area.
Don't forget to wear your PPE.