When choosing a weed killer for your lawn, it is important to adhere to the instructions for use. Some weed killers work on dormant grass, others have to be watered to activate. Then, of course, not all weed killers are safe and effective on every grass at any time, so applying the wrong herbicide on your lawn can be disastrous.
Weed killers consist of two types of herbicides: pre-emergent and post-emergent. Pre-emergent herbicides are normally used in spring and fall because they must be applied before weeds germinate. Once the herbicide is applied, it needs at least 1/4 inch of water to activate. Several herbicides can be used on zoysia (Zoysia), centipede (Eremochloa ophiuroides) and Bermuda grass (Cynodon dactylon) to control crab grass, annual grasses and broadleaf weeds. Safe weed killers include those that contain benefin, trifluralin, oryzalin, bensulide or pendimethalin.
Post-emergent weed killers should be used when a weed is visible, but small. Apply post-emergent herbicides when the soil is moist, air temperature is between 60 and 80 degrees Fahrenheit and when the grass is completely dormant or actively growing. Post-emergent herbicides tend to work best in liquid form, not granules. Safe options for zoysia grass and Bermuda grass to control broadleaf weeds include 2,4-D + MCPP + dicamba, bentazon, halosulfuron, imazaquin and MSMA to control nutsedges and kyllinga. Sethoxydim and atrazine post-emergent herbicides are safe for centipede grass.
If your lawn consists only of zoysia grass, you can use triclopyr for broadleaf weed control and it is very effective on violets and ground ivy. For improved control, apply it twice, at an interval of three to four weeks. Never use triclopyr on Bermuda grass or centipede grass. Use sethoxydim, if your lawn consists only of centipede grass and you need to remove or suppress bahia grass. It is also effective in controlling other annual grasses.
In warm weather, herbicides degrade soon after application, so a second application two months later is often required. Herbicides should not be applied to your lawn at certain times of the year because of potential injury to the lawn. You risk harming your grass if you apply post-emergent herbicide during the green-up period. Pre-emergent herbicides should not be used on new lawns or warm-season lawns that will be overseeded with a cool-season grass. All three of these grasses are warm-season grasses. Zoysia grass is hardy in U.S. Department of Agriculture plant hardiness zones 5 to 10. Centipede and Bermuda grass are hardy in USDA plant hardiness zones 7 through 10.
- University of Georgia College of Agricultural & Environmental Sciences: Weed Control in Home Lawns
- University of Arkansas Division of Agriculture Cooperative Extension Service: Home Lawn Weed Control
- Seedland: Climate Maps, Grass Type Chart & More
- Clemson University Cooperative Extension: Bahiagrass
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