Tired of hearing those stupid Scotts commercials about time to pre-emerge for crabgrass?  I am!  They start about mid January and get people all stressed out about something that in TN I have personally have NOT seen happen before April 1st in the last 16 years!  Get your turf pre-emerged by the end of March this year, and you will be just fine.  Soil temps are a bit warmer than I have ever seen them, but crabgrass seeds have NOT germinated yet.  Perhaps they might germinate in the third week of March, but its still no problem.  Keep using Prodiamine for another 10 days, and then switch to Dimension if your still procrastinating into mid April. Dimension pre-emergent will actually control small crabgrass that germinates before you get to apply it.  Its a good product for you through mid April.