Pest Notes: Introduction

Bermudagrass (Cynodon dactylon) is a perennial, warm-season plant that can be used as turfgrass but can also be an invasive weed. It can grow in a wide range of environmental and drought stress conditions. Bermudagrass was introduced from Africa (not Bermuda) in 1751 and is widely spread throughout the southwest and southern United States. It is found in most areas of California at elevations below 3,000 feet. Also called couchgrass, devilgrass, wiregrass, or dogtooth grass, bermudagrass is commonly found in gardens, landscapes, orchards, roadsides, vineyards, and industrial areas.

Bermudagrass often invades areas where desired turfgrass species are grown, reducing overall turf quality and decreasing the long-term sustainability of turfgrasses. In cool-season turfgrasses, bermudagrass may be considered an aesthetic problem because it goes dormant (turns brown) in the fall, making the lawn unattractive.

Identification and Biology

Bermudagrass is a low-growing, wiry perennial that has two types of creeping shoots: those aboveground (stolons or prostrate stems) and those belowground (rhizomes). The stolons and rhizomes are capable of rooting at the nodes and creating new plants as they grow out from the original plant. Fragments of stolons and rhizomes can also root and regrow if cut and left on or in moist soil. In areas where the soil has not been disturbed, rhizomes are usually shallow (1 to 6 inches). But where the soil has been spaded or tilled deeper than 6 inches, or in sandy soil, under sidewalks, and against solid structures such as building foundations or walls, the rhizomes may be deeper than 6 inches.

Bermudagrass leaves are generally smooth and pointed, with a conspicuous ring of white hairs at the junction of the blade and sheath. The stolons typically have a papery leaf sheath at each node. The stems root at the nodes in moist soil. Flowering stems are upright and bear a terminal group of three to seven spikelike branches, usually originating in a single whorl on the tip of the stem. Individual spikes on the seedhead of bermudagrass originate at the same point, are 1 to 2 inches long, and bear two rows of spikelets along one side of a flattened rachis (the central stem of the spike). The seedhead is similar to that of crabgrass (Digitaria spp.), but the spikelike branches on crabgrass usually originate about 1/8 to 1/4 inch apart at the end of the stem.

Bentgrass (Agrostis spp.), which also occurs as a patch or large mat in a lawn, may be confused with bermudagrass. Creeping bentgrass (A. stolonifera), the species most common in turf, has very fine leaves, stems, and stolons, but no rhizomes. Bermudagrass may also be misidentified as other grass species, such as nimblewill (Muhlenbergia shreberi) and zoysiagrass (Zoysia spp.). However, in comparison, bermudagrass can be distinguished by its hairy ligules while creeping bentgrass has tall membranous ligules, nimblewill has short membranous ligules, and zoysiagrass has ligules that are fringes of hairs.

Management

Bermudagrass is not an easy weed to control; the aggressive stolons and rhizomes make bermudagrass extremely difficult to control selectively in turfgrass, garden, or landscaped areas. It can be managed nonchemically with a persistent program of removal, or over large areas by cultivation and by withholding water during the summer to desiccate the stolons and rhizomes. Mulches of black plastic or geotextile landscape fabric can also be effective over large areas if light is excluded. Control with herbicides (Table 1) requires careful timing and often more than one application.

Cultural Control

Although bermudagrass tolerates some drought, it grows best when irrigated. If the area where the bermudagrass is growing can be dried without injuring any nearby ornamentals, withhold water to dry the stems and rototill or spade the area two or three times during summer months. This will bring rhizomes to the surface where they dry out. Raking to remove rhizomes and stolons will also help. If water is applied during the process or it happens to rain, the remaining bermudagrass is likely to regrow from fragments. A single, deep (down to 6 inches) cultivation may be adequate to bring most shoots to the surface, but the time required to dry the remaining rhizomes still buried in the soil will add additional weeks to months. Be careful not to cultivate bermudagrass if the soil is moist or the weed will spread, because cultivation chops the stems into segments and some of these segments could root and become new plants. While cultivating and drying can effectively kill established plants and rhizomes, these practices do not kill bermudagrass seeds in the soil.

Bermudagrass growth can be reduced by increasing shade from trees and tall shrubs. Shaded growth will be fine and spindly; plants are easier to remove than those growing in full sun. Shade from short shrubs or ground covers will not be effective; the bermudagrass will simply grow up through these plants. Because bermudagrass can spread vegetatively and by seed, it may be spread by clippings resulting from mowing. If such lawn clippings are to be used in the landscape, they should be thoroughly composted to kill seeds, rhizomes, and stolons to reduce the spread of this weed.

Mulching and Solarization

Mulch can be used in a variety of ways to manage bermudagrass. Black polyethylene film applied over bermudagrass to prevent sunlight from reaching the plant can effectively control established plants. Mow and irrigate the grass, place the plastic over the plants, and leave it for at least 6 to 8 weeks in summer. Placing plastic mulch over bermudagrass in winter will not control it due to its seasonal dormancy. Be sure that the plastic remains intact without holes, or bermudagrass will grow through the holes and survive. Bermudagrass control will be reduced if other plants are planted in holes made in the plastic.

Clear plastic mulching (solarization) is effective for eradication of bermudagrass plants and seed if it is applied during periods of high solar radiation. For instance, in California’s Central Valley, this means during June to August, whereas in coastal areas the best time may be August to September or May to June when fog or wind is most likely to be at a minimum.

Before applying the plastic, closely mow the bermudagrass, remove the clippings, and water the area well. Although it is not necessary to cultivate before solarization, shallow cultivation may improve control. Place clear, ultraviolet (UV)-protected polyethylene over the area; the clear film allows solar radiation to heat the soil and retains thermal energy, maintaining high temperatures for longer periods of time. The plastic should extend roughly 2 feet beyond the bermudagrass stolons to make sure the infested area is covered; it must be maintained intact for 4 to 6 weeks. Shade will reduce the effectiveness of solarization because it limits the amount of absorbed radiation.

Solarization works most effectively when there is no slope in the land or, if there is, the slope has a south or southwest exposure, thereby increasing the heat from the sun. Soil temperatures do not get as high under plastic placed on a north-facing slope; consequently, weed control will not be as effective. After solarization, do not cultivate the area deeper than 3 inches to avoid bringing weed seed into the upper soil layer. (See Pest Notes: Soil Solarization in Gardens & Landscapes).

It is important to highlight that suboptimal solarization treatments applied in early spring during low solar radiation and low soil and air temperature can actually promote bermudagrass growth.

Mulching with products such as wood chips is not effective against bermudagrass because the weed can push up through this mulch. If landscape (geotextile) fabrics are used under the mulch, however, control can be achieved. The fabric must be overlapped so the stolons do not grow between the fabric sheets. If there are holes or gaps in the fabric, control will be reduced because bermudagrass can grow through the holes.

Chemical Control

In most cases, bermudagrass can be controlled in ornamental landscapes and turf using postemergence herbicides. The best time to apply a particular herbicide depends on the type of herbicide and the situation where the weedy bermudagrass is growing. Postemergence herbicides are applied to actively growing bermudagrass foliage and stems during spring and summer. There are two basic types of herbicides that can kill mature bermudagrass: nonselective herbicides that kill most plant species and grass-selective herbicides that only kill plants in the grass family (Poaceae). In addition, there are some herbicides that will suppress bermudagrass, which might give a desirable turf species a chance to outcompete the weed.

Table 1. Herbicides registered in California for bermudagrass control.

Preemergence Synthetic Herbicide
Active Ingredient	Consumer Use
dithiopyr	Yes
oryzalin	Yes
pendimethalin	Yes
prodiamine	Yes
trifluralin	Yes

Postemergence Synthetic Herbicide
Active Ingredient	Consumer Use
clethodim	No
diquat	Yes
fluazifop-p-butyl	Yes
glyphosate	Yes
glufosinate-ammonium	Yes
sethoxydim	Yes
topramezone	No
triclopyr	Yes
pelargonic acid	Yes

Postemergence Naturally Derived Herbicide
Active Ingredient	Consumer Use
ammonium nonanoate	Yes
caprylic acid + capric acid	Yes
acetic acid	Yes
d-limonene	Yes
clove oil	Yes
fatty acids	Yes

Preemergence Synthetic Herbicides

Bermudagrass seedlings may emerge in turfgrass, garden, or landscaped areas that have been treated with postemergence herbicides because these herbicides do not control the seed or seedlings that have not yet emerged. Preemergence herbicides that affect new plants shortly after seed germination, such as trifluralin (Trifluralin 4EC), pendimethalin (Pendulum 3.3 EC), oryzalin (Surflan AS Specialty Herbicide), dithiopyr (Dimension Ultra 40WP and Dithiopyr 2EW), and prodiamine (Prodiamine 65 WDG), may be available to licensed pesticide applicators or consumer use, and can be used in established turf or landscape ornamentals.

Although preemergence herbicides are available to suppress bermudagrass germination from seeds, preemergence herbicide use is generally not a practical approach to controlling bermudagrass in turfgrass. The preemergence herbicide has the potential to suppress grass and broadleaf weeds germination, and to slow the encroachment of bermudagrass in turfgrass systems and landscape ornamentals. Repeated applications are often required for consistent control because bermudagrass seed is viable in the soil for multiple years. To control new seedlings more effectively, apply these herbicides before the seeds germinate. Do not use preemergence herbicides just before seeding or sodding a new lawn because they will negatively affect germination and root growth of the desired grass species. Always read the herbicide label recommendations.

Postemergence Synthetic Herbicides

Selective Herbicides. Selective postemergence herbicides to control or suppress bermudagrass include the active ingredients sethoxydim (Grass Getter), fluazifop (Fusilade II Turf & Ornamental Herbicide and Ornamec 170 Grass Herbicide), clethodim (Envoy Plus Herbicide), triclopyr (Turflon Ester Ultra), and topramezone (Pylex). Clethodim and topramezone are only available for sale to licensed pesticide applicators; the other active ingredients may be available for consumer use with different trade names in most retail garden outlets. This is not a complete list of all retail products; look for similar herbicides with the same active ingredient (See: Pesticide Active Ingredient Database).

Triclopyr and topramezone are selective herbicides that are primarily used to control broadleaf plants, but these may also suppress bermudagrass in cool season turfgrasses when label conditions are followed. Sequential applications of topramezone plus triclopyr may increase bermudagrass suppression. The herbicide topramezone has been used as a standard for bermudagrass control and can be applied safely to most cool-season grasses, including Kentucky bluegrass, tall fescue, fine fescue, and perennial ryegrass.

Selective postemergence herbicides can be used safely around most, but not all, ornamental trees, shrubs, and flowers. The product labels include lists of ornamental plants that may be injured by these herbicides. Do not use these herbicides in desired turf or near ornamental grasses.

Early spring is the best time to apply grass-selective herbicides (clethodim, sethoxydim, and fluazifop). For best control with these herbicides, make the first application in spring when new bermudagrass growth is less than 6 inches in length, then re-apply the herbicide before the regrowth reaches 6 inches again. Additional applications on regrowth may be needed through the spring and summer. It is important to be consistent with treating regrowth to eliminate the weed. Read the label of each product for information on the total amount that can be used per year per area. The best control is achieved when the bermudagrass is growing vigorously, with lots of leaf surface and is not drought stressed, dusty, or damaged by insects.

Nonselective Herbicides. Glyphosate is a nonselective herbicide that kills plants by translocating down into the root system, in addition to killing top-growth. For glyphosate to be most effective, it must be applied to bermudagrass that is actively growing, not drought stressed, and has enough leaf surface. Do not mow the weed for 2 to 3 weeks before treating. The best time of the year to apply glyphosate is during late summer when bermudagrass plants are storing carbohydrates in roots. After applying glyphosate, wait at least 7 days before mowing or cultivating the bermudagrass to maximize herbicide movement within the plant. Cultivation will bring the underground parts of the plant to the surface of the soil so they can dry. If left uncultivated, deeper rhizomes and roots may survive the first application and regrow.

Contact Herbicides. Some herbicides will suppress bermudagrass by damaging green stems and leaves through contact activity. Suppressing bermudagrass will not typically eliminate it permanently from an area, because these herbicides do not affect the roots or rhizomes, but it might be enough to foster the growth of a desirable turf species. Rigorous, repeated suppression may eliminate the weed if combined with control of bermudagrass seedlings.

Herbicides that can suppress bermudagrass include nonselective contact herbicides such as diquat (Diquat SPC 2L and Alligare Diquat Herbicide; diquat is commonly sold in formulation combination with other herbicides), glufosinate-ammonium (Finale XL T&O Herbicide), and pelargonic acid (Scythe). Use caution when applying nonselective herbicides as they will also damage desired turf.

Postemergence Naturally Derived Herbicides

There are some nonselective organic-approved and other naturally-derived herbicides available to residents that may suppress bermudagrass. These include ammonium nonanoate (Axxe), caprylic acid + capric acid (Suppress and Homeplate), acetic acid (Vinagreen and Green Gobbler 20% Vinegar Weed & Grass Killer), d-limonene (Avenger Weed Killer Concentrate), clove oil (Weed Zap), nonanoic acid (FireHawk Bioherbicide Concentrate), and fatty acids (Finalsan Herbicidal Soap). These contact herbicides can be used around bedding plants, flowers, ornamentals, turfgrass, landscape, and ornamental trees and shrubs, but they may injure desirable vegetation that they contact. Keep in mind that even naturally-derived herbicides can be harmful to humans and nontarget organisms, so always follow label directions, wear personal protective equipment, and store these herbicides properly.

Following the treatment of established bermudagrass, seed that is present in the soil may still be a source of future weed problems. Bermudagrass seed will not be controlled with any of the previously mentioned treatments except solarization. If bermudagrass seeds germinate in areas around ornamental plantings, the seedlings can be controlled with shallow cultivation, hoeing, or a thin layer of mulch.

References

Gonçalves CG, Brown AM, Basak S, McElroy JS. 2021. Response of seashore paspalum and bermudagrass to topramezone and triclopyr mixtures. Weed Technology, 35:501-508.

McCullough P. 2011. Bermudagrass Control in Southern Lawns. University of Georgia, College of Agricultural and Environmental Sciences, Cooperative Extension, Bulletin 1393

Stapleton JJ, Wilen CA, Molinar RH. 2019. UC IPM Pest Notes: Soil Solarization for Gardens and Landscapes. UC ANR Publication 74145. Oakland, CA.

UC IPM Pest Management Guidelines: Turfgrass.UC ANR Publication 3365-T. Oakland, CA.

Revised based on a previous version authored by DW Cudney, CL Elmore, and CE Bell.

Resources

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