Q. What is the best way to get rid of crabgrass?
A. If you have just a few isolated patches of this annual weed, you can either dig them out before they go to seed or spot-treat with an approved post-emergent herbicide spray. If your problem is more advanced, apply a pre-emergent herbicide in spring before the weeds emerge and before lilacs bloom. For severe infestations, a repeat application is recommended one month later. When treating large portions of the lawn, it is important to know what type of turf grass you have. Studies have shown that crabgrass favors lawns that are stressed, overwatered, mowed too frequently at too low a height and need an application of nitrogen-rich fertilizer.