Bermudagrass Control in Southern Lawns Patrick McCullough, Extension Specialist Bermudagrass is a warm-season perennial widely used Bermudagrass Identification for lawns in the southeastern United States. Although Bermudagrass has prolific rhizomatous and stolonifer- improved common (Cynodon dactylon (L.) Pers.) and ous growth during summer months that contributes to hybrid bermudagrasses (Cynodon dactylon x C. trans- persistence and competition with turfgrasses. Ber- vaalensis Burtt-Davy) have desirable qualities as turf- mudagrass leaves are folded in the bud with strongly grasses for heat, drought and wear tolerance, bermu- compressed, sparsely hairy sheaths. Leaf blades are dagrass is a problematic weed when grown in mixed generally short (0.125 to 0.25 inches wide), rough stands with other turf species. Centipedegrass (Er- along the edges and sharply pointed at the tips. Ber- emochloa ophiuroides (Munro) Hack), St. Augustine- mudagrass ligules have a fringe of hairs with a narrow grass (Stenotaphrum secundatum (Walt.) Kuntze), tall collar covered with long hairs (Figure 2). Seedheads fescue (Festuca arundinacea Shreb.) and zoysiagrass have three to five slender spikes that join at the top of (Zoysia spp.) lawns are often unable to compete with the main stem (Figure 3). bermudagrass populations during summer months. Selective control of bermudagrass is difficult but often warranted in order to maintain acceptable quality of the desired turfgrass species (Figure 1). Figure 2. Hairy ligules of Figure 3. Bermudagrass bermudagrass. plants. (Photo: P. McCullough.) (Photo: P. McCullough.) Preemergence Herbicide Control Preemergence herbicide use is generally not a practi- cal approach to controlling bermudagrass in mature turfgrasses. Siduron (Tupersan) is a preemergence herbicide for use during cool-season turf establishment for control of crabgrass and grassy weeds. Siduron has the potential to slow the encroachment of bermu- Figure 1. Bermudagrass in a tall fescue lawn. (Photo: P. McCullough.) dagrass in cool-season turfgrasses but often requires repeat applications for consistent control (Johnson and Carrow, 1989). Other preemergence herbicides have the potential to injure bermudagrass runners bordering a lawn (i.e., dinitroanilines) but turf managers should combination with atrazine to control bermudagrass not rely on the efficacy of these herbicides to prevent (Table 1). Ethofumesate is an unclassified herbicide bermudagrass encroachment. that has postemergence activity for grassy and broad- leaf weed control in nonresidential St. Augustinegrass Postemergence Herbicide Control and cool-season grasses. Ethofumesate has several Postemergence herbicides may be applied to suppress toxic effects in susceptible species, such as bermudag- bermudagrass populations and reduce competition rass, but arrested cell division appears to be the pri- with desirable turfgrasses. Repeat applications of se- mary mechanism of selectivity (Senseman, 2007). lective herbicides are needed for best results but may be injurious to the desirable species. Furthermore, tol- Atrazine inhibits photosynthesis in susceptible weeds erance to herbicides may vary by turfgrass cultivar and and is in the triazine herbicide family. Triazines inter- end-users should consult with local Extension special- fere with electron transport during photosynthesis and ists for application rates and recommendations. eventually leads to cell membrane destruction and cel- lular leakage. Susceptible weeds initially exhibit chlo- Bermudagrass Control in Centipedegrass rosis on leaf margins. Actively growing bermudagrass Centipedegrass is a popular low-maintenance lawn is sensitive to atrazine applications and its addition to species in Georgia. Centipedegrass generally has slow- ethofumesate treatments provides postemergence and er growth than bermudagrass with less potential for some residual control of bermudagrass. Atazine alone competition during the summer. Clethodim (Envoy, may provide some bermudagrass suppression but does others) and sethoxydim (Segment, others) are cyclo- not provide long-term control. hexenadione herbicides that inhibit lipid synthesis in grassy weeds. Sensitive species exhibit leaf injury Applications of ethofumesate with atrazine should be with reddish discoloration before significant necrosis. initiated during bermudagrass spring greenup (Mc- Carty, 1996). Herbicide regimens that begin on ac- Bermudagrass is sensitive to both clethodim and tively growing bermudagrass in summer will likely sethoxydim and repeat applications may suppress be ineffective. St. Augustinegrass often responds to populations in centipedegrass (Cox et al., 1999). Turf applications with stunted growth and discoloration. managers should schedule applications approximately Repeat applications should be made after 30 days or every three weeks during active growth. For best once turf has recovered from any potential injury. See results, add a nonionic surfactant at 0.25% v/v with the current edition of the Georgia Pest Management clethodim to enhance spray retention and apply no Handbook for rates and further information about ap- sooner than three weeks after spring greenup. Cer- plications for bermudagrass control. tain sethoxydim products (e.g., Segment) may have a built-in adjuvant already mixed in the formulation and Bermudagrass Control in Tall Fescue the addition of a surfactant is not required. For both and Zoysiagrass herbicides, turf managers should avoid mowing one Fenoxaprop and fluazifop are aryloxyphenoxy-propi- week before or after treatment. onate herbicides used for postemergence grassy weed control in tall fescue and zoysiagrass. These herbicides Bermudagrass Control in inhibit lipid synthesis in susceptible grassy weeds St. Augustinegrass similar to cyclohexenadiones. Sensitive weeds exhibit St. Augustinegrass is a major warm-season turfgrass injured leaf tissue with reddish discoloration while used for lawns in southern Georgia. St. Augustine- plant nodes become necrotic and die. Aryloxyphe- grass has desirable heat and drought tolerance but is noxy-propionate herbicides have no activity on broad- sensitive to many herbicides. Selective herbicides for leaf weeds but provide excellent grassy weed control. controlling grassy weeds, such as crabgrass and goose- grass, are limited in St. Augustinegrass lawns. Bermu- Fenoxaprop (Acclaim Extra) and fluazifop (Fusilade) dagrass infestations are also difficult to manage. may be used alone in tall fescue and zoysigrass lawns (Table 1). Fenoxaprop may also be used in residential St. Augustinegrass has good tolerance to ethofume- and nonresidential Kentucky bluegrass (Poa praten- sate (PoaConstrictor, Prograss), which may be used in sis L.), perennial ryegrass (Lolium perenne L.) and Bermudagrass Control in Southern Lawns 2 UGA Cooperative Extension Bulletin 1393 other cool-season turfgrasses. Fluazifop may be used aerification, should be delayed for seven days after in commercial and nonresidential turf. Generally, tall treatment. fescue has good tolerance to these herbicides. There is greater potential for injury on zoysiagrass than on tall Glyphosate requires optimum translocation in order to fescue from fenoxaprop or fluazifop treatments, espe- control bermudagrass rhizomes and plants emerging cially fine-textured varieties.Triclopyr (Turflon Ester, form lateral stems. Perennial grasses generally have Turflon Ester Ulta) at high rates (0.75 to 1 lb ai/acre) greater translocation of photosynthate from leaves to is injurious to bermudagrass, and tank mixtures with stems in fall than spring, which increases glyphosate fluazifop or fenoxaprop have been shown to reduce movement to rhizomes. Fall glyphosate applications tall fescue and zoysiagrass injury without compromis- generally control bermudagrass more effectively than ing control (McElroy and Breeden, 2006). The addi- summer treatments. Numerous glyphosate products tion of an adjuvant to tank mixtures of fluazifop with are available under a wide variety of trade names. new triclopyr formulations (e.g., Turflon Ester Ultra) Table 2 presents examples of glyphosate products, is unnecessary and may increase turf injury. trade names and distributors. See product labels for rates and mixing instructions for spot treatments of In Georgia, initial applications of fenoxaprop or fluazi- glyphosate for postemergence bermudagrass control. fop should be scheduled around June 1 and repeated every 20 to 30 days. Fluazifop alone should be ap- plied with a non-ionic surfactant at 0.25% v/v of spray Literature Cited solution. Acclaim Extra (fenoxaprop) does not require Cox C. J., L. B. McCarty, and J. K. Higingbottom. the addition of an adjuvant. See the current edition of 1999. Envoy (clethodim) for bermudagrass the Georgia Pest Management Handbook for rates and control and centipedegrass tolerance. Proc. South. application comments for fluazifop and fenoxaprop Weed Sci. 52:68. treatments for bermudagrass control in tall fescue. Johnson, B. J. and R. N. Carrow. 1989. Bermudagrass Nonselective Bermudagrass Control encroachment into creeping bentgrass as affected Spot treatments of nonselective herbicides are the by herbicides and plant growth regulators. Crop most effective method for controlling bermudagrass. Sci. 29:1220-1227. Glyphosate is a nonselective herbicide that is widely used for spot treatments of perennial weeds in turf- McCarty, L. B. 1996. Selective control of common grasses. Glyphosate is a foliar-absorbed herbicide that bermudagrass in St. Augustinegrass. Crop