Weed Management

Bert McCarty & Ted Whitwell, Turf and Weed Control Specialists

To download the 2013 Pest Control Guidelines for Weed Control, please click here.  (675 KB, PDF)

The best defense against weeds is a dense, vigorously growing turf.  By adapting the right grass to the site and following correct cultural management, including proper fertilization, mowing, and irrigation, weeds will not be able to compete as well as with the turf.  Before deciding to use any herbicide, diagnose first why the turf is thin and weeds are invading.  Correct the basic problem of unhealthy turf before using any herbicide.  Herbicides are not a substitute for sound cultural practices.

Deciding Which Herbicide to Use

The first step toward a successful weed management program is the accurate identification of the desirable and undesirable plants involved.  There are about 100 weeds that commonly occur in turfgrass.  These plants can be grouped as weedy grasses, grass-like weeds, sedges and broadleaf weeds.  Refer to Color Atlas of Turfgrass Weeds, Weeds of Southern Turfgrasses listed on page 2 of this publication or to Turfgrass Slide Monograph, Common Turfgrass Weeds, available from the Crop Science Society of America, as pictorial identification guides.

Next, determine if you wish to control weeds before planting (called Pre-plant).  This involves either fumigating which controls most pests such as weeds, diseases, insects, and nematodes or do you just want to nonselectively control the existing weeds.  If so, nonselective herbicides do not control weed seeds, insects, diseases, nematodes, etc., like fumigation does.
Table 1.  Pre-plant Nonselective Weed Control. (133 KB, PDF)

Next, do you wish to control weeds before they emerge (before you see them).  If so, then a preemergence (often abbreviated PRE) herbicide should be considered.  This involves applying the herbicide before the weed seeds germinate.  Refer to the tables on weed control efficacy by the various PRE herbicides and the one on turfgrass tolerance to decide which materials may be used for your situation.
Table 2.  Preemergence herbicide Efficacy Ratings. (128 KB, PDF)
Table 3.  Turfgrass Tolerance to Preemergence Herbicides. (130 KB, PDF)
Table 4.  Preemergence Herbicides for Putting Greens. (116 KB, PDF)
Table 5.  Pre-plant Herbicides.  (117 KB, PDF)
Table 6.  Preemergence Herbicides. (159 KB, PDF)

Weeds which have already emerged are controlled selectively in turf with postemergence (often abbreviated POST) herbicides.  The tables under Postemergence Herbicides should be consulted to determine weed susceptibility to various herbicides and more important, turf tolerance to these herbicides. 
Table 7.  Established Turfgrass Tolerance to Postemergence Broadleaf Herbicides. (1991 KB, PDF)
Table 8.  Established Turfgrass Tolerance to Postemergence Grass Herbicides.  (129 Kb, PDF)

Separate tables are provided on grass weed susceptibility and broadleaf weed susceptibility to the various POST herbicides.  Again, additional information is available in the larger tables on the specific products, trade names, application rates, weeds controlled, and important comment sections.
Table 9.  Guide to Grass Weed Control with Postemergence Turfgrass Herbicides. (128 KB, PDF)
Table 10.  Expected Control of Broadleaf Weeds with Turf Herbicides.  (259 KB, PDF)
Table 11.  Postemergence Herbicides. (247 KB, PDF)

If you know that sedges are your problem, refer to the nutsedge control section.  This lists products available, turf tolerance, weed susceptibility and additional information on each product.
Table 12.  Relative Sedge Control and Turf Tolerance to Various Herbicides. (124 KB, PDF)

Finally, the last table of the Weed Control section lists the most often used products by common names along with their corresponding trade names, manufacturers and/or distributors.
Table 13.  Postemergence Sedge Control. (132 KB, PDF)