Bermuda grass (Cynodon dactylon) is a perennial, warm-season turfgrass known for its aggressive growth habit. It spreads rapidly via above-ground runners (stolons) and robust underground stems (rhizomes), making it a highly invasive weed in lawns where it is not desired. Selective removal is challenging because Bermuda grass is a grass invading another grass, meaning common herbicides often cannot distinguish between the weed and the desirable turf. Eliminating this persistent invader requires a multi-season commitment combining cultural practices with targeted chemical strategies designed to protect the existing lawn.
Cultural Practices and Physical Removal Methods
Non-chemical methods are best suited for small, isolated infestations or as a long-term strategy to weaken the Bermuda grass. Manual removal requires diligence, as the deep, wiry rhizomes must be completely extracted to prevent regrowth. Simply pulling surface runners is ineffective; a shovel or trowel must be used to dig out the entire root mass, typically six inches or more of soil, and dispose of it properly.
For localized patches, soil solarization uses heat to kill the grass and its seeds. This involves mowing the area short, watering it thoroughly, and covering the patch with a sheet of clear plastic sheeting (1 to 6 mil polyethylene). The plastic must remain in place for four to eight weeks during the hottest part of the summer to generate soil temperatures lethal to the Bermuda grass.
Adjusting routine lawn care can favor the existing turf over the invasive Bermuda grass, which thrives in full sun and low-cut conditions. Increasing the mowing height of cool-season grasses, like tall fescue, to between 3.5 and 4 inches shades the soil surface, suppressing growth. Adopting deep, infrequent watering and avoiding summer fertilization of cool-season lawns also reduces the ideal growing conditions for the warm-season invader.
Selective Chemical Strategies for Cool-Season Turf
When the desirable turf is a cool-season variety (e.g., tall fescue, Kentucky bluegrass, or perennial ryegrass), selective chemical control is viable. These grasses are physiologically different from warm-season Bermuda grass, allowing certain herbicides to target only the unwanted grass. The most effective selective post-emergent herbicides are ACCase inhibitors, which disrupt a key enzyme in grassy weeds.
Active ingredients like fluazifop (Fusilade II) and fenoxaprop (Acclaim Extra) are commonly used to suppress Bermuda grass in cool-season lawns. A professional option is topramezone (Pylex), often tank-mixed with triclopyr (Turflon Ester) for enhanced control. These selective applications require multiple treatments, typically three to five applications spaced three to four weeks apart during the active growing season.
Triclopyr, combined with a grass-specific herbicide, improves the overall control of Bermuda grass in cool-season turf. Proper application is necessary, as over-application or use during turf stress can still injure the desirable grass. Always consult the specific product label for the maximum annual application rates to avoid damaging the lawn.
Selective Chemical Strategies for Warm-Season Turf
Selective control of Bermuda grass within other warm-season lawns (e.g., Zoysiagrass and St. Augustinegrass) is difficult because both the desired grass and the weed share similar physiology. In Zoysiagrass, the active ingredients fluazifop and fenoxaprop can be effective. However, Zoysia is more sensitive than cool-season grasses, and applications may cause temporary yellowing or growth reduction.
Including triclopyr in the spray solution can act as a safener, reducing temporary injury to Zoysiagrass while maintaining Bermuda grass control. Sequential applications are required, usually involving a series of treatments applied four weeks apart when the Bermuda grass is actively growing. This multi-application approach targets the extensive underground network of rhizomes.
Selective removal in St. Augustinegrass is exceptionally difficult because it is highly sensitive to most herbicides that kill Bermuda grass. An advanced approach involves tank-mixing fluazifop with a proprietary safener called metcamifen, found in some professional products. This combination allows fluazifop to target Bermuda grass without significant injury to the St. Augustine turf. Without this specialized safener, homeowners often resort to spot-treating with non-selective herbicides like glyphosate, requiring the killing of both grasses, followed by replugging or resodding the treated area.
Maximizing Effectiveness Through Timing and Application
Effective chemical control relies on precise timing; the herbicide must be applied when the Bermuda grass is actively growing and translocating nutrients to its root system. Applications should begin in late spring or early summer when the grass is fully green and growing vigorously, continuing through mid-August. Treating the grass when it is dormant or stressed by drought or heat reduces effectiveness and increases the risk of damaging the desirable turf.
The application technique is equally important, requiring a non-ionic surfactant (NIS) to help the herbicide penetrate the waxy leaf surface. This is necessary because Bermuda grass has a protective coating that can repel the herbicide solution. Best results are achieved using a calibrated sprayer to ensure uniform coverage of the target weed without excessive runoff.
A successful eradication program requires patience, as a single application only kills the exposed leaves and runners. Sequential applications, spaced three to four weeks apart, are necessary to eliminate emerging growth from the extensive rhizomes and stolons. For cool-season lawns, fall applications are often the most impactful because the Bermuda grass is storing energy for winter dormancy, drawing the herbicide deep into its root system.