In my years of working with people to establish quality turf and control many of its problems, I have come across many misconceptions people have about lawn establishment and control.
Misconception number 3: The lawn should be de-thatched every spring to maintain a healthy lawn.
Although some lawns with very heavy thatch may need this approach, aerating is a much better solution to eliminating thatch. It allows air, water, and fertilizer to more deeply penetrate the soil and allows microbial action to break down the thatch.
This is best done in the early fall when grass is less stressed. Fall application does not interfere with pre-emergent and is the best time for reseeding if necessary.