To prevent crabgrass in my lawn I use products with Dithiopyr (brand name Dimension). You can find multiple products with Dithiopyr, but this year I’m using Jonathan Green Green-Up with Crabgrass Preventer.
You can see the Dithiopry under active ingredients. It will prevent the crabrass from growing and will also kill crabgrass in it’s early stages. I can’t find Jonathan Green products in most big box stores – I bought this bag at a local hardware store. You can also order online.
This is a granular product that I spread with my 50lb Earthway rotary spreader. There is a slightly smaller version you can buy for less. I like this spreader because it has large rubber wheels and holds a lot of material. I had to assemble it which took some time. I use a setting of 14 on this spreader and that seems to work well for distributing at the right amount.
I applied this crabgrass preventer in mid-April here in Pennsylvania. It will prevent the crabgrass all season long.