The best way to control crabgrass is with a pre-emergent control and now is about the time to apply it. Crabgrass grows every year from seed left by the previous years crop. Be aware that the pre-emergent will also kill off grass seed at the same time so this is a multi-step process. You can't kill the crabgrass and re-seed at the same time. There are MANY brands of crab grass controls. Head to your local garden center (not a Lowes/Home Depot) and ask a couple of questions. They will get you hooked up. Best to go sooner rather than later......