University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Think Ahead to Crabgrass Control in 2000

February 24, 2000

Crabgrass was a major lawn weed last season, as conditions were ideal for development. If you had crabgrass problems last year, you probably are concerned about stopping it in 2000. We have plenty of time to act, but here's an overview of your options to keep crabgrass out of your lawn.

Crabgrass is a warm-season annual grass. No matter how many crabgrass plants appeared in your lawn last year, they are all dead. To have crabgrass here in 2000, seeds in the soil must germinate into new plants. This will not occur until soil temperatures get close to 60 degrees and stay there for several consecutive days, which most likely is not until late May or early June. So remember, you have plenty of time.

Sound lawn management practices help prevent crabgrass from becoming a problem. Mowing height has a major impact on crabgrass. Mow between 2 1/2 and 3 inches and there will be fewer crabgrass plants in your lawn. Also avoid frequent watering, especially frequent light sprinklings.

Crabgrass often invades bare soil in lawn areas that are disturbed in late spring or early summer. If possible, hold off lawn establishment or renovation work until late summer to avoid potential crabgrass problems. The same holds true for destructive practices such as dethatching.

Several preemergence herbicides (weed killers) are available to use in spring for
crabgrass control. These need to be applied to the lawn before crabgrass germinates. Late April into early May is the suggested time for applying preemergence crabgrass herbicide in our area. If April is unusually warm, apply by late April, otherwise early May is not too late.

Most preemergence crabgrass herbicides are found as a combination with lawn fertilizer at garden supply stores, so the crabgrass prevention and spring fertilization can be done at the same time. Follow the rates given on the bag.

One of the management problems associated with preemergence herbicides is seeding or overseeding practices. With the exception of a herbicide called siduron, all preemergence annual grass weed killers will also damage germinating desirable grass seed. Siduron may be found as lawn starter fertilizer with crabgrass preventer.


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