The key is the timing. Pre-emergent herbicides MUST be applied BEFORE crabgrass seed germinate. If Bob and other lawn owners choose one of the products above and put it out on March 1, 2004. I think summer crabgrass control will be much better.hat I found shocked me! The data show that soil temperatures reached 52 degrees F. on Feb. 24 in 2000, Feb. 25 in 2001, Mar. 14 in 2002 and Mar. 4 in 2003. My timing advice has been wrong ! To get good crabgrass control in Atlanta you should apply the pre-emergent on March 1, not March 15.