Question
I live in Louisiana and have many issues with my lawn, at first I thought that I would put down pre-emergent and then later on soil and lay seed (Bermuda Grass to be exact).  However, I've decided that sod would be my best bet so my question is, Can I lay sod 3 or 4 months after I put down the pre-emergent (crabgrass preventer to be exact).  I really want to put it down in the spring but i will wait until fall if there is a chance it will take.

Thank you

Answer
When to Apply Crabgrass Preventer

Crabgrass seeds germinate in the early Spring when the temperature of the surface soil rises into the 50s and 60s.  Once the seeds germinate, the opportunity for prevention is passed.  So, applying the preemergent early is key.  Scotts Turfbuilder with Halts Crabgrass Preventer (our preemergent of choice this year because that抯 what was available at the big box) recommends spreading the preemergent before the days are regularly in the 80s.  We think that抯 much too late.  Once the days are regularly in the 60s and 70s, the seeds will be germinating and sprouting small plants.  Instead, apply preemergents very early in the season, while the temperatures are still in the 50s.  In Baltimore County, MD, this means spreading the preventer before April 1.  

Scotts crabgrass preventer can be applied only twice per year, once in the early Spring and again in the late Summer if desired.  The limitation has more to do with the Turfbuilder nutrients in the product rather than the crabgrass preventer.  A product that only contains the herbicide could be applied more frequently.  That said, we think it makes sense to spread preemergent only in the early Spring, while focusing on building up the cultured turf for the rest of the year.
Don抰 Plant Grass Seed | Avoid Garden Areas

Because preemergents prevent seed germination, they should be carefully applied so as to avoid garden and other new growth areas.  You should also avoid planting any type of grass seed within 3-6 months after applying preemergent.  In other words, plan to plant new turf only in the Autumn.