Weed Identification and Control
Bert McCarty, Turf and Weed Control Specialist
To download the 2014 Pest Control Guidelines for Weed Control, please click here. (602 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. (39 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. Additional information is available in the larger tables on the specific products, trade names, applicationrates, weeds controlled, and important comments. A separate table is provided which lists currently registered products for bentgrass and/or bermudagrass golf greens.
Table 2. Preemergence Herbicide Efficacy Ratings. (39 KB, PDF)
Table 3. Turfgrass Tolerance to Preemergence Herbicides.
(41 KB, PDF)
Table 4. Preemergence Herbicides for Putting Greens. (22 KB, PDF)
Table 5. Pre-plant Herbicides. (22 KB, PDF)
Table 6. Preemergence Herbicides. (66 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. (39 KB, PDF)
Table 8. Established Turfgrass Tolerance to Postemergence Grass Herbicides. (37 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. (36 KB, PDF)
Table 10. Expected Control of Broadleaf Weeds with Turf Herbicides. (155 KB, PDF)
Table 11. Postemergence Herbicides. (155 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. (29 KB, PDF)
Table 13. Postemergence Sedge Control. (41 KB, PDF)
Managing Herbicide Resistant Weeds
- Herbicide resistant weeds in turf, such as Poa annua, spurges, goosegrass, and crabgrass are becoming more prevalent. Fortunately, this can be contained if prudent action is taken. The following table summarizes the main herbicides used in turf including their timing (Pre- vs Post-emergence), their mechanism of action within plant (how they control them), and various active ingredients. Rotating between and tank-mixing herbicides with different mechanisms of action are keys to delaying or preventing herbicide reistant weeds from dominating a population.
Table 14. Managing Herbicie Resistant Weeds, Timing, Mechanism of Action, Active Ingredient (Trade Name Example). (27 KB, PDF)
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