Pre-emergent herbicides are very effective at controlling crabgrass before it emerges when warm weather arrives. It doesn’t kill existing crabgrass. But, by using a pre-emergent herbicide in early spring, you can effectively prevent crabgrass during the summer wherever the herbicide was applied. Sprinkle by hand, spreader or use a garden hose attachment to spray on the grass, depending on what type of herbicide you buy. If you use a spreader to apply the herbicide, make sure you water the area after application with a garden hose or sprinkler in order to activate the herbicide. Follow package instructions and measure your lawn so that you use the proper amount. Calibrate your spreader carefully. Be sure that the herbicide you choose is safe to use on your grass. Don’t dethatch or aerate after you’ve applied herbicide.
Many “weed and feed” fertilizer products contain crabgrass preventatives. These can be a good choice to use in spring because you can fertilize and apply a pre-emergent herbicide in one application.