Ariel Whitely-Noll: Timing is critical for crabgrass prevention. When should you act? – The Topeka Capital-Journal

Ariel Whitely-Noll| Special to The Capital-Journal

Crabgrass is a common lawn and garden weed, best controlled in the spring. As discussed a few weeks ago, the timing is essential for effective control of crabgrass, and products applied too early or too late in the season are wasted.

In April, typically between April 1 and 15, crabgrass pre-emergence herbicide should be applied to areas that have had crabgrass in previousyears. These products do not kill the crabgrass seedsbut rather kill the crabgrass plants just as they are emerging from the seed. This means most pre-emergent products will have no effect on existing crabgrass plants, which is why we rely on proper spring timing.

A pre-emergence applied in the late spring or summer will do nothing to stop crabgrass from invading your lawn or garden.

Due to the limited time these products are effective after application, generally around 60 days or less, there is a signal we can take from mother nature to help us ensure were applying the products at the proper time. Look for the redbuds to bloom. Eastern Redbud trees are native to Kansas and abundant in our landscapes.

When they reach full bloom, apply crabgrass preventer to ensure the product will be well timed with crabgrass germination.

As with all chemical applications, pay close attention to the product label and directions. Products that include pendimethalin (Scotts Halts) and Team (Hi-Yield Crabgrass Control) will require a follow-up application. Dimension or Barricade do not require follow-up applications.Dimension and Barricade last much longer in the environment and have a wider window of application and longer persistence in the soil, resulting in season-long control.

Dimension can also have an effect on young crabgrass plants and works favorably with tall fescue, perennial ryegrassand Kentucky bluegrass seedlings. Again, label directions should be followed. The safest schedule to prevent crabgrass pre-emergent products from affecting new lawns is to seed in the fall and apply pre-emergent for crabgrass in the spring. Dimension may also be sold under the name of its active ingredient, dithiopyr, and Barricade may be sold by its active ingredient, prodiamine.

Crabgrass preventers should be applied before fertilizer to reduce the likelihood that the grass will put on growth too early in the season. Many products combine pre-emergent and fertilizer, but the below products do not.

Barricade: Howard Johnson Crabgrass Control Plus with 0.37 Prodiamine 00-00-07.

Pendimethalin: Scotts Halts.

Team (Benefin + Trifluralin): Hi-Yield Crabgrass Control.

Dimension: Hi-Yield Turf & Ornamental Weed and Grass Stopper.

If you have not already, make sure to test your soil every three to five years and follow those recommendations for fertilizer. Oftenwe find lawns and gardens are overfertilized, which can sometimes cause issues, such asbrown patch, in lawns. For more information about soil testing, visit our website at http://www.shawnee.k-state.edu/lawn-garden/soil-testing.html.

The mention of commercial products and trade names is for educational and informational purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Please make sure to read all product label thoroughly and follow those instructions exactly.

Ariel Whitely-Noll is the horticulture agent for Shawnee County Research and Extension. She can be reached at arielw@ksu.edu.

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Ariel Whitely-Noll: Timing is critical for crabgrass prevention. When should you act? - The Topeka Capital-Journal