Crabgrass is a type of weed that plagues most lawns. Crabgrass grows outward in a star like pattern that will cover the soil and smother other grasses. What makes this weed so hard to kill is that you it is an annual and it only needs to be 50 degrees fahrenheit to germinate. There are many ways to kill crabgrass that involve chemicals. Some of these chemicals work, but do take caution, especially when it comes to Fescue seed or sod.
Crabgrass preventers will prevent grass seed from germinating, so if you plan to plant fescue seed, do not apply a crabgrass preventer to your lawn. If necessary, you can apply a lawn weed control on growing weeds before temperatures exceed 90 degrees.
Just take caution and really research everything before you apply, even if you hire a big company known for their applications because they are usually some of the biggest killers of lawns.