Before using herbicides to control pesky turf weeds, lawn care operators should follow approved preventive, cultural and mechanical turfgrass management practices.
Preventive practices. Turfgrass managers should strive to prevent the accidental introduction or spread of weeds over a turfgrass area. Preventive practices include using weed-free seed, sod, sprigs, container plants, mulches and topsoil.
State and federal laws prohibit the presence of noxious weed seeds in seed sold for agricultural purposes. However, most weed species are not classified as noxious weeds. Therefore, the end buyer should purchase high-quality turfgrass seed and vegetative planting materials that do not contain weed seeds. Similarly, only mulches and topsoil that do not contain problem weed species should be purchased.
Other preventive practices are: preventing weeds from going to seed, cleaning mowers and earth moving equipment between different sites, and, if possible, controlling weeds along ditch banks, fence rows and other adjacent areas.
Cultural practices. The first line of defense against weeds is to follow cultural practices that promote vigorous growth and turfgrass development. Weeds do not easily invade turfgrasses that are properly fertilized, watered and mowed at the correct height and frequency.
Weeds appear primarily in bare or thin turfgrass areas. These thin or bare areas may be due in part to one or more of the following: improper mowing procedures, improper watering, improper fertilization, excessive amounts of thatch, the use of nonadapted turfgrasses and insect and disease control failure.
The impact of good cultural practices on a weed control program cannot be overemphasized. Adhering to recommended fertility programs, water requirements, mowing heights and schedules, and controlling diseases and insects will significantly increase turfgrass competition with weeds. And, it will also improve the tolerance of turfgrasses to herbicides and increase the effectiveness of the weed control program. The use of herbicides without following approved cultural practices will not result in a high quality, weed-free lawn.
Mechanical methods. Many weed species do not tolerate frequent mowing. Adhering to mowing frequency and cutting height guidelines will help limit the development of many weed species. Hand-pulling annual weeds is safe and effective. However, it is time consuming and is not effective for the control of most perennial weeds. Hand-pulling a “strange” or “new” weed when it first appears in the lawn will help to prevent the spread of that weed. When properly maintained in their area of adaptation, most turfgrass species are highly competitive with weeds. – Tim Murphy
The author is an extension weed scientist at The University of Georgia Cooperative Extension Service, Griffin, Ga.