Controlling crabgrass after it emerges

Crabgrass has emerged in many turf and lawn areas, and there are several herbicide options available for post-emergence control.

The recent, warm temperatures have pushed crabgrass to the surface in many areas. Crabgrass I’ve observed has progressed quickly from emergence to 3-4 leaf stage or beyond quickly. Thin turf areas, low cut turf (such as golf course fairways) or turf near sidewalks, driveways and roadsides where temperatures are warmer are usually the first place to look to find crabgrass.

Crabgrass in turf. Photo credit: Kevin Frank, MSU

The best defense against crabgrass invasion as recommended by Michigan State University Extension is maintaining a healthy, dense turf stand by mowing high and fertilizing. Crabgrass is a warm season annual that thrives at high temperatures. If post-emergence crabgrass control is in your future, here’s a herbicide primer.

Post-emergence control

Post-emergence control is generally more effective when crabgrass is younger before it has tillered. As crabgrass matures, postemergence control becomes more challenging and multiple applications spaced two to three weeks apart are necessary to achieve control.

MSMA is no longer available for selective grassy weed control in lawns or commercial turf. MSMA can be used on golf courses and sod farms. There are several options for controlling crabgrass in cool season turf: Drive (a.i. quinclorac), Acclaim Extra (a.i. fenoxaprop-ethyl) and Tenacity (a.i. mesotrione) are all effective for post-emergence control.

Quinclorac provides excellent control of crabgrass at almost any growth stage (seedling or gorilla-sized) and is very safe when applied to new seedings. Quinclorac has the added benefit of enhancing broadleaf herbicide activity when tank-mixed with other broadleaf specific herbicides. Quinclorac also is excellent for control of some broadleaves (white clover and dandelion) on its own. Fenoxaprop-ethyl is generally not as effective on larger or more mature crabgrass as quinclorac, but can provide excellent control of other grassy weeds, such as goosegrass, that are not effectively controlled by quinclorac. Mesotrione is also very effective for postemergence crabgrass control.

Controlling crabgrass at establishment

For those that are considering establishing new turfgrass this summer, controlling crabgrass can be the difference between success and starting over again in the fall. Tupersan (a.i. siduron) is the traditional standby for controlling weeds during seeded turfgrass establishment. Newer to the scene is Tenacity, which can also be used safely at the time of seeding.

Always read, understand and follow the label directions. Mention or exclusion of specific products does not represent an endorsement or condemnation of any product by Michigan State University.

Dr. Frank’s work is funded in part by MSU’s AgBioResearch.

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