How to Kill Crabgrass With Herbicide

Overview

Crabgrass (Digitaria spp.) is a fast-spreading annual weed that's found throughout North America. The grass appears in the early summer and can quickly overwhelm a flower bed or a poorly kept lawn before dying off during the cooler fall season. Gardeners can use a fusion of manual removal and chemical treatments to keep crabgrass at bay and protect the beauty and health of their backyard or lawn.

Step 1

Trim your lawn with a lawn mower if you are trying to kill crabgrass that's growing among your turfgrass. Regular mowing keeps the crabgrass from developing seeds and spreading and, combined with chemical control methods, will help to successfully eradicate the weed.

Step 2

Dig out the crabgrass manually with a handheld spade. This is ideal for isolated bunches of crabgrass. Slide the spade under the center of the crabgrass bunch to uproot it.

Step 3

Treat the ground with a chemical control if manual removal is not feasible. Spray the area with a pre-emergent herbicide like pendimethalin or benefin. This kills the crabgrass seeds and keeps them from germinating. Apply such herbicides in the early spring.

Step 4

Follow the pre-emergent herbicide with a post-emergent herbicide like clethodim or fluazifop. Such chemicals are selective and will kill crabgrass without damaging the turfgrass. If you're trying to remove crabgrass that's not growing in turfgrass, any standard non-selective herbicide, such as glyphosate, will work effectively against the weed.

Tips and Warnings

  • After mowing crabgrass, rinse down the mower equipment so that you don't spread crabgrass seeds to new lawn areas the next time you mow.

Things You'll Need

  • Lawn mower
  • Spade
  • Pre-emergent herbicide
  • Post-emergent herbicide

References

  • "Ecological Management of Agricultural Weeds"; Matt Liebman, et al.; 2007
  • "The Lawn Bible: How to Keep It Green, Groomed and Growing Every Season of the Year"; David Mellor; 2003
  • University of California: Crabgrass Management Guidelines
  • University of Minnesota: Crabgrass Control
Keywords: kill crabgrass, crabgrass herbicide, erradicate crabgrass

About this Author

Josh Duvauchelle is an editor and journalist with more than 10 years' experience. His work has appeared in various magazines, including "Honolulu Magazine," which has more paid subscribers than any other magazine in Hawaii. He graduated with honors from Trinity Western University, holding a Bachelor of Arts in professional communications, and earned a certificate in applied leadership and public affairs from the Laurentian Leadership Centre.