Weed Wizard: Controlling Nutsedge C 867-9
- Full Text
Mark Czarnota, Extension Horticulturist
Published with minor revisions on Sep 13, 2011.
Nutgrass is a difficult weed to control in the landscape. There are approximately 20 genera of sedges in Eastern North America, but the genus Cyperus contains the worst weeds. The two most notable weedy representatives from this genus are yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus). These sedges will be the most commonly encountered in landscapes and turf.This publication discusses controlling nutsedge in the landscape.
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Nutgrass is a difficult weed to control in the landscape. There are approximately 20 genera of sedges in Eastern North America, but the genus Cyperus contains the worst weeds. The two most notable weedy representatives from this genus are yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus). These sedges will be the most commonly encountered in landscapes and turf. They both are herbaceous perennial plants that primarily reproduce from tubers. Tuber production among sedges is rare. In fact, of all the known sedge species in the United States, only yellow and purple nutsedge produce tubers.
Pennant (metolachlor), Basagran T/O (bentazon) and Image (imazaquin) are selective herbicides for controlling yellow and purple nutsedge in the landscape. Pennant is a preemergence herbicide for the control of yellow nutsedge. Basagran T/O, a selective postemergence herbicide, works best on controlling yellow nutsedge in certain ornamentals. Image, a selective postemergence herbicide, works best on controlling purple nutsedge in selected ornamentals.
Unfortunately, there is not a selective postemergent herbicide that effectively controls both yellow and purple nutsedge. Since there is no herbicide that selectively controls both sedges, it is important to apply the right chemical to the right sedge.
Sedgehammer (old trade name is Manage) (halosulfuron) is a postemergence herbicide for controlling both yellow and purple nutsedge in turfgrass. It also can be used as a non-selective, post-directed application for the control of yellow and purple nutsedge in established woody ornamentals. Roundup (glyphosate) can also be used as a non-selective post-directed application for the control of yellow and purple nutsedge.
Basagran T/O effectively controls only yellow nutsedge, while Image effectively controls only purple nutsedge. With the inability of these chemicals to control both sedges adequately, it is important to identify the differences between yellow and purple nutsedge so you can apply the proper chemical to control the targeted sedge. In flower, yellow and purple nutsedge are easy to distinguish between one another (Figures 1 and 2). Yellow nutsedge flowers are yellowish while those of purple nutsedge are purplish. Many times, however, you will encounter nutsedge plants that are not flowering, and you will have to rely on vegetative characteristics to identify these plants. Yellow nutsedge leaves have pinched tops, while the leaf tips of purple nutsedge are keeled (just like a boat, see Figure 3).
Applying the herbicide at the proper time is important for controlling sedges. As with all preemergence herbicides, control will be poor if the herbicide is applied after the plant is emerged. Pennant will not provide good control of yellow nutsedge after the leaves have emerged. For best postemergence control of yellow and purple nutsedge, apply herbicides after the foliage has emerged and is at least 4 to 6 inches high. This will assure adequate foliage to effectively absorb the herbicide. Basagran T/O requires approximately three to five days before herbicide symptoms appear. Image requires approximately seven to 14 days before herbicide symptoms appear. Image requires the use of a non-ionic surfactant (0.25% V/V), and Basagran T/O requires the use of a crop oil (1.0% V/V) or a nonionic surfactant (0.25 % V/V).
Basagran T/O and Image can be applied over-the-top of selected ornamentals (Table 1).
Table 1. Ornamentals labeled for over-the-top applications of Basagran T/O and Image.
|Basagran T/O (5 teaspoons / 1 gallon of water treats approximately 1,000 ft2). Don’t forget to add a surfactant or crop oil.||Ajuga, English Ivy, Liriope, Mugo Pine, Pachysandra|
|Image (0.5 ounces / 3 gallons of water and spray to wet).||Yucca, Juniper sp. (see label), Liriope, Pachysandra|
Research at the University of Georgia has indicated that one application of Sedgehammer can be applied over-the-top of several in-ground, well-established ornamentals with little to no damage. Although this is an off-label application, if a severe infestation of nutsedge is encountered, it may be your only viable option. Plants with limited safety to the active ingredient halosulfuron include daylily (Hemerocallis species), iris (Iris species), mondograss (Ophiopogon species), liriope (Liriope species) and ornamental grasses (Miscanthus and Pennisetum cultivars). Other woody species have been tested with limited damage. This would be considered an off-label application, and it would be recommended that you test the herbicide on a small area of ornamental plants, wait two to three weeks and evaluate desirable ornamentals for damage before treating an entire area.
Before using any pesticide, be sure to read and follow the label instructions.
Other Control Methods
Nutsedges are not good at competing with other plants for light, space and nutrients. To help reduce nutsedge infestations in ornamental beds, it is important that some type of mulching material be used to cover bare soil. If possible, hand weeding and cultivation on a regular basis can also help reduce nutsedge populations.
C 867-9 |
with minor revisions on
Sep 13, 2011.
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