MANAGING LAWN WEED PROBLEMS

FOR IMMEDIATE RELEASE
May 1, 2008

Two of the primary weed concerns in home lawns are crabgrass and dandelions. Since one of these is a grass and the other a broadleaf, management of the two is different. Let's look at crabgrass first. There is still a little time before this weed will appear in lawns, but prevention is the key to control. There are both cultural and chemical control options to consider, according to Bill Lindenmier, Extension Educator, Crops Systems, with University of Illinois Extension.

First, understand the target weed. Crabgrass is a warm-season annual grass. No matter how many crabgrass plants appeared in your lawn last year, they are all dead. Crabgrass can only reappear in 2008 from germinating seeds. Crabgrass will not start germinating until soil temperatures get close to 60 degrees and stay there for several days. Soil temperature will normally be much lower than air temperature. Most preemergence crabgrass herbicides are found in combination with lawn fertilizers, so crabgrass prevention and spring fertilization can be done at the same time. This type of weed and feed product needs 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. April was not unusually warm, other than a few days, so early May should not be too late.

Follow the rates given on the bag. If you do not receive rain within a week after application, it would be a good idea to water to get the herbicide activated. One word of caution; except for siduron, all preemergence herbicides for crabgrass will also damage germinating desirable grass seed. Siduron may be found as lawn starter fertilizer with crabgrass preventer.

Crabgrass prefers full sun, moisture, and thin lawns that allow light to hit the soil. Sound lawn care practices to allow for thick, vigorous lawns that shade the soil help prevent crabgrass from becoming a problem. Lindenmier says mowing height perhaps has the most impact on crabgrass. Mow between 2 1/2 and 3 inches or even a little higher and there will be fewer crabgrass plants in your lawn. The higher the lawn is mowed the longer the roots will be, and the better the lawn will be able to handle stress.

In addition, avoid frequent watering, especially frequent light sprinklings. If possible, hold off lawn establishment or renovation work until late summer to avoid potential crabgrass problems from appearing on open soil areas in lawns.

Dandelion and creeping Charlie are tough broadleaf weeds that we can control by applying herbicide either in fertilizer as mentioned with crabgrass control or by spot spraying a herbicide with a combination of active ingredients including 2,4-D, dicamba, MCPP, triclopyr and others. These products are very safe when used according to the label, but of course be careful not to let these products drift onto flowers, since they will do a good job controlling desirable broadleaves, also. The difference in managing broadleaves is that we want to treat weeds about the time they are blooming, since obviously they have already emerged. So, now is about the right time for controlling these two weeds, also. Lindenmier would recommend not using a pre-emergence grass herbicide or post emergent broadleaf herbicide on lawns until they have been established for at least a full year. As always please read and follow label directions. For more information call U of I Extension Master Gardener Hotline at 815/732-2191. You may call anytime with questions. A Master Gardener is available in the Ogle County office on Mondays Wednesdays and Fridays from 9 a.m. to noon. Another place to have your questions answered is on the Internet on the U of I Extension web site at www.extension.uiuc.edu/ogle or go to our Hort Corner at www.urbanext.uiuc.edu/hort .