Crab grass is a grassy weed that grows aggressively in the garden and yard. It is very difficult to control; but with manual pulling, along with an herbicide, it is possible to keep it manageable so your plants and grass can thrive. As with any herbicide, it is essential that you read the label for the correct dilution (if any), dosing and application methods, as well as when you should reapply. Also, herbicides designed to kill crab grass either work before the crab grass is growing (pre-emergent) or after it is growing (post-emergent).
Pre-Emergent Selective Herbicides
Benefin, bensulide, dacthal, oryzalin, pendimethalin and trifluralin are examples of pre-emergent selective herbicides that are used to kill crab grass. They are considered selective herbicides because they kill weeds, including crabgrass, not the other plants or desired grass growing around them. Always read the label to check where the herbicide is safe to use, because not all are the same.
Apply pre-emergent herbicides in late winter or early spring before crab grass germinates and begins to grow. You can also apply a pre-emergent herbicide after pulling crab grass in order to prevent new seedlings from growing.
Post-Emergent Selective Herbicides
Dithiopyr, fluazifop, poast and sethoxydim (plus oil) are examples of post-emergent selective herbicides. They are designed to kill crab grass and other broadleaf weeds after they grow. However, the younger the crab grass is, the more likely the herbicides will work. Like other selective herbicides, read the label to know where they are safe to use.
Glyphosate, pelargonic acid and glufosinate-ammonium are examples of non-selective herbicides that will kill any vegetation they come in contact with. They are extremely effective on actively growing crab grass but must be applied with more caution than other herbicides and on an almost perfectly still day. Immediately rinse any vegetation you accidentally spray with your hose.