Here is Lesson 6 - "Weed Problems in Lawns" in our Lawn Challenge Series from the University of Illinois. terry
General Weed Management Concepts for Lawns
Poor soils, improper care, or neglect commonly cause weed invasions in lawns.
Identifying the weed and trying to determine why it has become a problem is the first step in dealing with lawn weeds. Some weeds are good indicators of underlying problems. For example, ground ivy (creeping Charlie) readily invades lawns in shade and with poor soil drainage, while knotweed is a plant able to survive in compacted soils. Crabgrass typically invades lawns that are mowed too short or watered too often. Clovers may be a sign of low fertility. Dandelions may adapt to a range of conditions. An assortment of weeds may indicate overall poor conditions for lawn grasses and/or poor management.
Sound lawn care practices may prevent weed invasions such as this.
After identifying the weeds present, step two for controlling weeds should be to review lawn care practices and make adjustments as needed to assure a good stand of grass. Sound lawn care practices should promote a healthy, vigorous turf able to prevent and compete with weed invasions. These practices include proper selection and establishment, fertilization, watering, mowing, thatch management, and related practices.
The third step is removal of existing weeds. Pulling by hand is one option; be sure to get as much of the root system as possible. There are a number of herbicides available for weed control, specific to the type of weed to be controlled.