Timely Herbicide Use Can Control Crabgrass

By Trish Svoboda

Crabgrass can become an issue for homeowners during this season. According to K-State horticulture specialist Cynthia Domenghini, timely use of an herbicide can mitigate issues with the weed.

Domenghini said that around May 1st is when crabgrass usually begins to germinate. She recommends April 15th for applying crabgrass preventer to allow time for the active ingredients to spread in the soil. Crabgrass preventers, also known as pre-emergence herbicides, inhibit the growth of crabgrass seeds into adult plants.

She notes that the preventers do not affect existing plants, so they must be applied before germination.

“Preventers do not last forever once applied to the soil. Microorganisms and natural processes begin to gradually break them down soon after they are applied. If some products are applied too early, they may have lost much of their strength by the time they are needed.” said Domenghini.

Most crabgrass preventers lose effectiveness after 60 days. Barricade and Dimension control crabgrass all season from a single application. Domenghini said Barricade can be applied as early as March 1st, and Dimension can be applied earlier than April 15th.

“We recommend that homeowners apply crabgrass preventers before fertilizer so that the grass isn’t encouraged to put on too much growth too early,” Domenghini said. “However, it may be difficult to find products that contain pre-emergent without fertilizer.”

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