Early spring = Fertilize with crabgrass preventer — Do not seed after this is down.
early summer – fertilize and apply broad leaf herbicide (sometimes together in same product)
early – mid summer – spray with quinclorac to kill crabgrass that exists.
fall = aerate and overseed and fertilize
The above is what I would do if you have some bare spots to seed. Fall is always best.
To get rid of crabgrass completely (doesn’t ever 100% happen). you NEED to have preventer down every year for 5 years.
So if you care to have a decent lawn (key word is care). you should at least do those 4 steps (don’t have to overseed if not needed) every year.
So what I found is for my 1.5 acre lawn I can barely buy the products for what it costs for Green Care to come and do it for me for the whole year. ($325)
So i decided to not buy a sprayer and let them do it so I can fish in my spare time.