Pre-emergent crabgrass control cannot be used at this time.  It prevents the germination of grassy type weeds; however it also prevents the germination of desirable turfgrass seedlings.  It cannot distinguish the difference between these two types of seeds.  Broadleaf weed control should not be used until after the third mowing.  Before weeds can be controlled every effort must be made to establish the new seedlings to their full potential.