The best way to treat for crabgrass is to use a pre-emergent herbicide. These treatments work to prevent crabgrass from sprouting and becoming mature in the first place, allowing your grass the full time it needs to grow during the season.
Early spring is the ideal time to take preventative measures. By applying pre-emergent herbicides, we can help to eliminate the chances of annual grasses establishing a foothold in your lawn this growing season.
Pre-emergent herbicides literally form a barrier in the top inch of your soil which blocks annual grass seeds from sprouting. They are irrigated or incorporated into the soil by way of rainfall and will react with the weed seedlings as they sprout from seeds. Pre-emergent herbicides react with growing roots or other plant parts to halt growth through the lifetime of the pre-emergent treatment. Young seedlings that may have sprouted before the pre-emergent was applied are eliminated as well. It's important to note that the treatment works by eliminating growth in sprouted seeds, and not the seeds themselves, which is why regular re-application to continue growth prevention is necessary.
There will always be annual grass seeds in your lawn. In fact, crabgrass seeds can remain in your soil for up to 30 years before sprouting. Annual grass seeds can also be blown into your yard from miles away in windy conditions. For these reasons, yearly applications of pre-emergent herbicides are necessary for maximum prevention and control.
Pre-emergent herbicides have proven to be relatively safe for people and pets, so long as proper instructions are followed. It's important to give your lawn some time after an application of the treatment, meaning that one should stay off of the lawn until the treatment is dry and be sure to always follow label recommendations. It is also important to be deliberate about the timing and placement of any pre-emergent treatment. Pre-emergent herbicides prevent all types of seed from germinating, so it's a good idea to wait six to eight weeks after an application before planting any new grass seed.