Crabgrass Control

Each year we invest some time and money trying to control annual grassy weeds such as crabgrass and goosegrass. Sometimes our control is so good and uniform I wonder if it really needs to be done each year. I believe that answer is yes. In the photo you can see the area on the right has pre-emergent crabgrass control and the are on the left does not and it is almost 100% infected.