It only makes ‘Cents’ to skip crabgrass control products in Montana

Kari Lewis, MSU Extension - Glacier county

Recently I heard an ad advertising crabgrass control for lawn grass.  Crabgrass is one of the most infamous annual weeds in lawns, but it’s rarely found in Montana.  Quackgrass, however, IS commonly found in Montana, and is often confused with crabgrass.  Quackgrass is a coarse-bladed grass that grows in clumps and crowds out desirable grasses such as Kentucky bluegrass.  There are some key differences between these two weedy grass species which is why crabgrass control methods do not work for controlling quackgrass. 

Crabgrass is an annual weed that is relatively easy to control with crabgrass controlling products.

Quackgrass is a common grassy, perennial weed in Montana,
that is often confused with crabgrass.
Photo courtesy of University of Missouri Extension.

Quackgrass, however, is a perennial weed that is more challenging to control.  Clients often wonder why a crabgrass control product is not working and the reason is, the weed is likely quackgrass, not crabgrass.  2,4-D containing products, such as Weed-B-Gone or Weed-N-Feed, are not effective at controlling quackgrass either, as 2,4-D is for controlling broadleaf weeds, such as dandelions, not for controlling grassy weeds like quackgrass.  Quackgrass requires the use of a non-selective herbicide, such as Roundup. 

The recommended control for quackgrass is glyphosate, or more commonly known as Roundup, which moves down into the plant and kills the plant’s root system, which is critical for perennial weeds such as quackgrass.  Glyphosate is a non-selective herbicide, meaning it will kill any plant it touches.  Therefore, if applying glyphosate to quackgrass, be very careful to avoid damaging surrounding grass, shrubs, or trees.  To ensure the glyphosate is applied only to the quackgrass, wear rubber gloves and apply the glyphosate directly to the quackgrass with a sponge or paintbrush.  If there’s a large patch of quackgrass present, be prepared to reseed the patch to a desirable grass species within 10 to 14 days after glyphosate treatment.  Always read and follow label directions when applying glyphosate, or any herbicide. 

If you have any questions regarding identification of grassy lawn weeds or control of quackgrass, be sure to contact your local MSU Extension office and visit this Montana resource http://diagnostics.montana.edu/plant/topics/quackgrass.html. 

Photo from University of Missouri Extension, http://extension.missouri.edu/p/IPM1024-31.