As their name implies, pre-emergent herbicides prevent crabgrass plants from emerging in the first place. They work by killing off any would-be crabgrass plants soon after their seeds germinate. Pre-emergents won’t work if they aren’t applied prior to seed germination, though, so it’s important to make sure they’re on your lawn before crabgrass grows. Plus, since there will always be crabgrass seeds trying to grow in your lawn, yearly applications are necessary for ongoing control.
Also, keep in mind that pre-emergents will stop good grass seeds from growing too. Therefore, you should wait six to eight weeks after a pre-emergent application if you want to reseed your lawn.
With a one-two punch of good lawn care practices and pre-emergent herbicide applications, your turf will be much less likely to suffer a crabgrass infestation.
