P&PDL Picture of the Week for
March 27, 2006

Preemergent Crabgrass Control Applications

Glenn Hardebeck, Turfgrass Research Agronomist, Agronomy Department

Crabgrass is often overlooked or misidentified until it matures to the point of forming seed heads and stolons, which begin creeping across the lawn.  By this time it may be well into the summer and the crabgrass plant is nearing the end of its lifecycle.  Crabgrass is an annual warmseason grass.  It grows from seed each year, thrives during hot summer weather when our desirable grasses are having difficulties, turns purple during cool fall nights and finally dies with the onset of frosts in the fall.  Each crabgrass plant has the potential of producing upwards of 10,000 seeds, which can lay dormant in the soil for many years.  Therefore, once a lawn develops a crabgrass problem, preemergent crabgrass control should be considered thereafter.

Preemergent crabgrass applications have to be made before the seed germinates.  Crabgrass generally germinates early April in southern Indian to late April in northern Indiana.  With the uncertainty of Mother Nature it is better to apply early rather than late.  A late application will miss early germinating crabgrass seeds while an early spring application can control crabgrass well.  Although the herbicide is broken down by soil microbes, the microbes are inactive due to cool soil temperatures allowing the herbicide to remain in the soil until well after the soil warms up.

So if you’re planning on applying crabgrass preventer this spring don’t procrastinate any longer.

Photos courtesy of Dan Weisenberger, Turfgrass Research Agronomist, Agronomy Department

Click image to enlarge

Crabgrass seedling

Young crabgrass plants are easy to miss.  It’s important to apply crabgrass preventers before the seeds germinate.

Crabgrass stand

Growing crabgrass plants appear light green with a wide leaf blade during mid May into June.

Crabgrass tillered

Mature crabgrass plants are aggressive during the summer heat forming seedheads and stolons, which creep through the lawn rooting down and continuing to grow and spread along the way.

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service