Crabgrass in New Sod: Source and Control

Question: New topsoil and sod installed early July. Crabgrass invasion since. Unscreened topsoil? How to eliminate?

Reality

Crabgrass seed is everywhere—blows in before sod is even finished. Several control products available, but frost kills it—late season, may not be worth treating. Use pre-emergent in late February to prevent next year. Focus on thickening turf now—thick grass = fewer weeds.