Bermudagrass

Images above: Left: Bermudagrass growth habit (Jack Clark, University of California). Right: Bermudagrass shoots growing from stolons (University of California Division of Agriculture and Natural Resources).

Identification

Other common names:  scutch-grass, dogs-tooth grass, wire-grass, couchgrass

Family:  grass family, Poaceae

Habit:  Long-lived, prostrate, fine-leaved perennial grass that spreads by runners and rhizomes (Holm et al. 1977).

Description:  Leaf sheaths and collars are smooth in the young seedlings.  Leaves are rolled in the bud, smooth on both surfaces.  The ligule is membranous, fringed, and very short.  Auricles are absent.  The mature plant has erect stems up to 1.6 ft (49 cm) tall that arise from stolons and rhizomes.  Leaves are linear, 2-6.3” (5-16 cm) long by 0.08-0.2” (0.2-0.5 cm) wide, sometimes lightly hairy on the upper surface, and hairy on the lower surface.  The collar region has an inconspicuous membranous ligule with a fringe of 0.01” (0.025 cm) long hairs.  Sheaths are sometimes hairy on lower leaves, and have long, tufted hairs on their margins in the collar region.  The root system is rhizomatous and stoloniferous, with fibrous roots branching from nodes.  Inflorescences are located at the end of stems in an arrangement of 3 to 9, 1.2-4” (3-10 cm) long spikes.  Spikelets are 0.08-0.1” (0.2-0.3 cm) long and awnless; they consist of one flower that produces one light brown, egg-shaped seed.

Similar species:  Creeping bentgrass (Agrostis stolonifera L.) also spreads through stolons and rhizomes.  However, it can be distinguished by its long, membranous ligules, smooth leaves and sheaths, and dense, open panicles.

Management

Bermudagrass is considered the worlds worst grass weed that infests 40 crops in over 80 countries (Holm et al. 1977).  The tenacity with which it survives inhospitable conditions have led to its development as a forage and turfgrass species as well as to its success as a weed (Mitich 1989).  Management generally requires considerable effort and persistence since intermittent tillage only serves to spread the extensive network of rhizomes and stolons (Mitich 1989).  Consequently, preventing its invasion into non-infested fields is critical, for example, by cleaning machinery before entering a field and digging out any clumps when they first appear.

Near the northern limits of its range where the soil freezes in winter, plow the field in the fall and work the rhizomes to the soil surface where they will freeze (Muenscher 1980).  Plants will emerge from rhizomes that escape, but this can reduce the infestation.  In regions with predictable drought, moldboard plow during drought, leaving a rough surface so that air penetrates the soil.  One plowing during a protracted drought period will substantially reduce bermudagrass (Phillips 1993).  For a more rapid and thorough kill, repeat tillage at 4-7 day intervals until the soil is completely dry to the full depth of plow layer, and then continue this for at least an additional two weeks.  This will kill rhizomes to the depth of tillage.  When rains return or the field is irrigated, follow up with cultivation and hand hoeing in the row to eliminate sprouts from deep rhizomes. 

Competitive cover crops are effective for suppressing bermudagrasss.  Plant a dense stand of rye, winter oats or winter barley in the fall.  Harvest this for grain or forage and plow under the stubble.  Plant a highly competitive summer cover crop like cowpea or velvetbean.  The one year of dense shade and early summer soil disturbance will greatly suppress bermudagrass (Muenscher 1980).  Heavy competition from taller plants is particularly useful against bermudagrass due to its short stature.  Also, the shade will lower leaf and soil temperatures, which will slow growth of this heat loving species.  High density planting of the cover crops is critical to ensure rapid canopy closure and dense early shade.

Ecology

Origin and distribution:  Bermuda grass is native to tropical Africa or possibly southern Asia, but now occurs in most places between 45° N and 45° S latitudes (Holm et al. 1977).  It occurs throughout the U.S.A. except for some of the most northern parts of the Midwest and New England (USDA Plants), but it is a serious weed primarily in the southern half of the country.

Seed weight:  0.31-0.36 mg (Keeley and Thullen 1989); 0.23 mg (Holm et al 1977).

Dormancy and germination:  Removing bermudagrass hulls increases germination.  Seeds sold for forage seedings in Texas had 6-9% germination with hulls but 24-31% with the hulls removed (Holt et al. 1951).  Bermudagrass has negligible germination in the dark at any constant temperature.  Fluctuating temperatures promote germination, and day/night temperature differences of more than 30 °F (17 °C) are more effective than more moderate fluctuations.  Light and nitrate further increase germination in a fluctuating temperature environment but are ineffective if the temperature is constant.  Seeds will germinate in anaerobic conditions if other factors are favorable (Morinaga 1926).

Seed longevity:  No information on survival of bermudagrass seeds could be located.  If the species is like most perennial grasses, the seeds disappear from the soil within a few years (Lewis 1973, Rampton and Ching 1970).

Season of emergence:  In a California study, shoots began emerging from culm plugs when soil temperature at 2” (5 cm) reached 63 °F (17 °C).  The rate of shoot emergence was slow in March and April but increased rapidly after mid-May (Keeley and Thullen 1989).

Emergence depth:  Seedlings emerge best from about 0.25” (0.6 cm) but emerge reasonably well from the top 1” (2.5 cm).  None emerge from deeper than 2” (5.1 cm) (Keeley and Thullen 1989).  The rhizomes can occur as deep as 40” (1 m) and shoots can emerge from rhizomes below the plow layer (Holm et al. 1977).  However, shoots are less likely to emerge from rhizome fragments below 6” (15 cm) than from rhizome fragments at 2-4” (5-10 cm) (Phillips 1993).

Photosynthetic pathway:  C4  (Elmore and Paul 1983).

Sensitivity to frost:  Bermudagrass grows poorly in cold weather, and quickly ceases growth after frost (Keeley and Thullen 1989).  Exposed rhizomes are killed by freezing (Muenscher 1980).  In contrast, the species thrives in climates where the temperature commonly reaches 100 °F (38 °C) (Holm et al. 1977).

Drought tolerance:  Bermudagrass becomes dormant during extended droughts and then sprouts from rhizomes when moisture is again available (Holt et al. 1951).  However, its productivity and rate of clonal expansion respond strongly to water availability (De Abelleyra et al. 2008).  Patch expansion is linearly related to the plant available water, which is the ratio of volume of water in the soil to the water storage capacity of the soil (De Abelleyra et al. 2008).  Rhizomes can recover from short periods of low soil moisture, but will not resprout after seven days of desiccation in completely dry soil.  The species can also survive prolonged flooding (Holm et al. 1977, Mitich 1989).

Mycorrhiza:  Bermudagrass is mycorrhizal (Wu et al. 2011).

Response to fertility:  Bermudagrass is capable of surviving low fertility conditions.  However, the growth of plants establishing from seeds respond strongly to N, P or K applied alone, and growth is even more rapid if the fertility is balanced.  Established plants respond strongly to N fertilizers but respond to P and K only if N is not limiting (Holt et al. 1951).

Soil physical requirements:  Bermudagrass can grow on any soil type from sand to heavy clay, but it grows best on medium to heavy textured soils that are well drained but remain moist (Holm et al. 1977, Mitich 1989). 

Response to shade:  Bermudagrass does not tolerate shade.  In a series of experiments, the size of bermudagrass clones increased exponentially in response to the amount of sunlight received (De Abelleyra et al. 2008). 

Sensitivity to disturbance:  Bermudagrass can withstand frequent, intensive defoliation, and selections of the species are used for golf greens which are mowed daily to less than 3/8” (1 cm) (McCarty and Miller 2002).  In temperate regions of the U.S.A., carbohydrate reserves in the rhizomes increase through the fall, reach a peak in winter, decline in the spring with the rapid production of new shoots, and reach a low in midsummer (Holm et al. 1977).  Consequently, the species is most sensitive to disturbance of the rhizomes during midsummer.

Time from emergence to reproduction:  Small sod plugs, similar to what might be dispersed by tillage machinery, produced flowers in 10-15 weeks when planted in March to May in southern California.  Those planted in June through September 1 flowered in as little as 4 weeks and produced seed within 8 weeks.  A planting October 1 did not flower (Keeley and Thullen 1989).

Pollination:  Bermudagrass is wind pollinated (Wilken and Hannah 1998).

Reproduction:  Most reproduction is by fragmentation of rhizomes and runners during tillage (Mitich 1989).  Small 4-node rhizome fragments buried at about 2.5" (6 cm) in the spring produced 3.3-6.6 ft (1-2 m) of runners and 12-28” (30-70 cm) of rhizome in four weeks.  These had approximately 20-40 runner nodes and 10-23 rhizome nodes.  Runner fragments with 4 nodes tended to produce more runners and fewer rhizomes than rhizome fragments, but produced a roughly similar number of total nodes.  Heavier 4-node fragments of both types produced a greater length of runners and rhizomes (Fernandez 2003).  Small sod plugs planted 8” (20 cm) apart in a row in southern California produced up to 85 rhizome nodes/ft2 (916 nodes/m2) with the greatest density produced by plantings in March and July.  Plugs planted in March produced 6,800 seeds/ft2 (73,000 seeds/m2), with seed production declining with later plantings through the spring and summer (Keeley and Thullen 1989).

Dispersal:  The seeds can survive at least 50 days submerged in water (Holm et al. 1977).  They disperse in irrigation water (Kelley and Bruns 1975) and probably also by overland flow and in streams.  Seeds pass through cattle and are spread with the manure (Burton 1948, Cudney et al. 1992).  The small seeds of bermudagrass can lodge in the fur of animals and thereby be dispersed over large areas (Radosevich and Holt 1984).  Seeds do not shatter easily and are moved about with hay (Holm et al. 1977).  Most dispersal, however, occurs by movement of vegetative parts.  Tillage implements can drag rhizome and runner fragments long distances within fields (Guglielmini and Satorre 2004).   Rhizomes and runners get carried in mud on cattle and on farm machinery.  Pieces of sod can float down streams.  Runner fragments may be included in hay or lawn clippings used as mulch. The species has been dispersed between ports in ship's ballast and in packing materials (Holm et al. 1977). 

Common natural enemies:  Domestic cultivars of bermudagrass are attacked by a mirid bug (Trigonotylus doddi) (Buntin 1988), fall armyworm (Spodoptera frugiperda), leafhoppers (mainly Carneocephala flaviceps, Exitianus exitiosus, Graminella nigrifrons, G. sonora, Draeculacephala balli, and Cuerna costalis), and planthoppers (mainly Delphacodes propinqua and Sogatella kolophon) (Lynch and Burton 1994).  The species probably has similar susceptibility when growing as a weed.

Palatability:  Bermudagrass is a high quality forage when young but quality deteriorates substantially as it matures (Holt et al. 1951).  Mature bermudagrass can cause poisoning of cattle, horses and goats, possibly due to a fungal infection in the foliage, but cases are rare (Burrows and Tyrl 2006).

References:

• De Abelleyra, D., A. M. C. Verdú, B. C. Kruk, and E. H. Satorre.  2008.  Soil water availability affects green area and biomass growth of Cynodon dactylon.  Weed Research 48:248-256.
• Buntin, G. D.  1988.  Trigonotylus doddi (Distant) as a pest of bermudagrass: damage potential, population dynamics, and management by cutting.  Journal of Agricultural Entomology 5:217-224.
• Burrows, G. E., and D. J. Tyrl.  2006.  Handbook of Toxic Plants of North America. Blackwell:Ames.
• Burton, G. W.  1948.   Recovery and viability of seeds of cerain southern grasses and lespedeza passed through the bovine digestive tract.  Journal of Agricultural Research 76: 95-103.
• Cudney, D. W., S. D. Wright, T. A. Shultz, and J. S. Reints.  1992.  Weed seed in dairy manure depends on collection site.  California Agriculture 46:31-32.
• Elmore, C. D., and R. N. Paul.  1983.  Composite list of C4 weeds.  Weed Science 31:686-692.
• Fernandez, O. N.  2003.  Establishment of Cynodon dactylon from stolon and rhizome fragments.  Weed Research 43:130-138.
• Guglielmini, A. C., and E. H. Sattore.  2004.  Effect of non-inversion tillage and light availability on dispersal and spatial growth of Cynodon dactylon.  Weed Research 44:366-374.
• Holm, L. G., D. L. Plucknett, J. V. Pancho, and J. P. Herberger.  1977.  The World's Worst Weeds: Distribution and Biology.  The University Press of Hawaii: Honolulu.
• Holt, E. C., R. C. Potts, and J. F. Fudge.  1951.  Bermudagrass research in Texas.  Texas Agricultural Experiment Station Circular 129:5-25.
• Keeley, P. E., and R. J. Thullen.  1989.  Influence of planting date on growth of bermudagrass (Cynodon dactylon).  Weed Science 37:531-537.
• Kelley, A . D., and V. F. Bruns.  1975.  Dissemination of weed seeds by irrigation water.  Weed Science 23:486-493.
• Lewis, J.  1973.  Longevity of crop and weed seeds: survival after 20 years in soil.  Weed Research 13:179-191.
• Lynch, R. E., and G. W. Burton.  1994.  Relative abundance of insects on bermudagrasses and bahiagrasses. Journal of Entomological Science 28:120-129.
• McCarty, L. B., and G. L. Miller.  2002.  Managing Bermudagrass: Selection, Construction, Cultural Practices, and Best Management Strategies.  Wiley: Hoboken, New Jersey.
• Mitich, L.  1989.  Bermudagrass.  Weed Technology 3:433-435.
• Morinaga, T. 1926.  Effect of alternating temperatures upon the germination of seeds.  American Journal of Botany 13:141-158.
• Muenscher, W. C.  1980.  Weeds, Second Edition.  Cornell University Press: Ithaca, New York.
• Phillips, M. C.  1993.  Use of tillage to control Cynodon dactylon under small-scale farming conditions.  Crop Protection 12:267-272.
• Radosevich, S. R., and J. S. Holt.  1984.  Weed Ecology: Implications for Vegetation Management.  Wiley: New York.  p. 57.
• Rampton, H. H., and T. M. Ching.  1970.  Persistence of crop seeds in soil.  Agronomy Journal 62:272-277.
• Wilken, D., and L. Hannah. 1998.  Cynodon dactylon (L.) Pers. (Poaceace): Bermuda Grass.  Santa Barbara Botanic Garden for Channel Islands National Park.  http://www.npwrc.usgs.gov/resource/literatr/aprs/lit/cynodon%20dactylon.doc
• Wu, J., B. Sun, Y. Wang, G. Xin, S. Ye, and S. Peng.  2011.  Arbuscular mycorrhizal fungal colonization improves regrowth of bermudagrass (Cynodon dactylon L.) after cutting.  Pakistan Journal of Botany 43:85-93
• USDA Plants, Natural Resources Conservation Service.  http://plants.usda.gov