• Topics: Environmental Horticulture  | Lawn Herbicides  | Weed Management in Ornamentals and Turf  |  Lawn Weeds  |  Brecke, Barry J  |  Unruh, Joseph Bryan 

Response of Turfgrass and Turfgrass Weeds to Herbicides¹

This document is best viewed in pdf format at http://edis.ifas.ufl.edu/pdffiles/WG/WG07100.pdf

Weeds are seldom a serious problem in a well-managed, vigorous turf. Encroachment of weeds into turfgrass is usually a sign of a weakened stand due to such factors as insects, diseases, nematodes, inadequate watering, improper mowing, poor fertilization, incorrect pH, etc. Herbicides may temporarily remove the weeds; however, unless the basic cause of the weakened turf is corrected, the weeds will continue to return as a problem.

If a herbicide is needed, the following tables can serve as a guide in deciding which one to use. The first step is to determine which herbicide can be safely used on the turfgrass species. Table 1 and Table 2 list the expected turfgrass tolerance to certain herbicides. Table 3 and Table 4 list the effectiveness of preemergence and postemergence herbicides in controlling common weeds found in turf. Since no single herbicide will control all weeds, accurate weed identification is essential before selecting a herbicide. It is important to note that the information contained in the tolerance tables refers to the turf's tolerance to a single application of the named compound when applied alone (or in mixtures as noted). Chemical “cocktails” where two or more herbicides are mixed together may result in increased turfgrass injury, and caution should be taken when using such mixtures.

Read the label of the herbicide selected to be certain the herbicide is labeled for the desired use. All herbicides are not labeled for use in home lawns. Accurate calibration and application are critical.

Excessive overlaps may result in turfgrass damage, while failure to obtain proper overlap may result in strips without weed control. Preemergence applications should be made before weed seed germinate. In general, for summer grass weed control, application should be approximately February 1 in south Florida, February 15 in central Florida, and March 1 in north Florida. Because adequate soil moisture both prior to and following application is necessary for effective weed control, avoid spraying during times of drought. Do not use a weed and feed type product every time the lawn is fertilized and be careful not to apply over the roots of sensitive ornamentals and trees.

Postemergence applications should be made when weeds are small. For hard-to-control perennial weeds, multiple applications are usually most effective but these may be damaging to turfgrass. Warm temperatures (70-80°F) generally increase activity, but yellowing may result when applications are made when temperatures are hot (greater than 85°F). To ensure good coverage, herbicides should be mixed with 25 to 30 gallons of water per acre perapplication. Two applications, using the low rates suggested on the label, spaced 7 to 10 days apart, are often most effective. Read the label and follow suggested rates and use restrictions.

The information in the following tables is not to be considered as recommendations for use of herbicides on turfgrasses, but as resource material to enhance the understanding of turfgrass responses to herbicides.

Table 1

PAGE 1. 

Table 2

PAGE 2. 

Table 3

PAGE 3. 

Table 4a

PAGE 4. 

Table 4b

PAGE 5. 

Table 4a cont.

PAGE 6. 

Table 4b cont.

PAGE 7. 

Table 5

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Table 6

PAGE 9. 

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.

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