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In those situations, selective herbicides have been developed to control weeds of warm-season turfgrasses. Inorganic chemicals (ammonium sulfate, urea, and tricalcium arsenate) were the first turfgrass weed control chemicals (Hansen, 1921). Their effectiveness was very limited. Auxin growth regulators (e.g., 2,4-D; dicamba; mecoprop; and related compounds) were the first synthetic organic herbicides. Developed secretly during World War II, they became widely used in 1947 as postemergence herbicides against broadleaf (dicotyledonous) weeds. Auxin growth regulators are generally destructive to St. Augustinegrass and centipedegrass. Symmetrical triazine herbicides (e.g., atrazine) were adopted by Florida sod growers about 1958 as the main postemergence herbicides for broadleaf weed control in St. Augustinegrass and centipedegrass (White and Busey, 1987). Because of its high potential for leaching into the surficial aquifer, atrazine cannot necessarily be depended on for future weed control in Florida turfgrass. It was supplemented in the late 1970's by asulam (Asulox) (Neel et al., 1979). Asulam may be used for grassy weed control, but it requires multiple applications, and the manufacturer has since backed off from supporting it's use in sod. Alligatorweed is normally an aquatic plant under biocontrol by the alligatorweed flea beetle, Agasicles hygrophila Selman and Vogt, but it has become a sod production problem without a good chemical control. Metsulfuron-methyl (Escort, DMC), which was effective, was removed from turf use about 1994, after only about 3 years on the market, but has recently been granted a 24-C labeling through Third Party Registration. The auxin growth regulators (e.g., 5 oz. 2,4-D/acre) give only fair results at rates which are not damaging to the St. Augustinegrass. Blanket crabgrass and smallflowered Alexandergrass are other serious sod weed problems in need of control. Chemical weed control in bermudagrass is based on postemergence compounds: auxin growth regulators, e.g., phenoxy herbicides such as 2,4-D, for broadleaf weeds and repeat applications of organic arsenicals, e.g., MSMA, for grassy weeds, supplemented by metribuzin (Fermanian et al., 1980; Johnson, 1975a; Johnson, 1980) as a "kicker" for hard-to-control goosegrass. At the same time, soil pH must not be too high, or else the metribuzin can be very harmful. The goosegrass must not be mature or else metribuzin efficacy is reduced. Because of seasonal use, the control of goosegrass on athletic fields is very difficult. Athletic field managers attempt to reduce the use of herbicides during seasons of player activity, thus there is a brief treatment window. Diclofop-methyl (Illoxan) is a postemergence control of goosegrass labeled for golf courses only (Murdoch and Nishimoto, 1982; McCarty, 1991; McCarty et al., 1991). Fluazifop (Fusilade) (Johnson, 1992) and fenoxaprop-ethyl (Acclaim) (Dernoeden, 1989) are useful in bermudagrass suppression in zoysiagrass.
Preemergence chemicals show less specificity among turfgrass species than do postemergence herbicides. Those which are the safest and most effective are oxadiazon (bermudagrass, St. Augustinegrass, and zoysiagrass only) which can even be used on newly sprigged bermudagrass, prodiamine (season-long control, Bingham and Shaver, 1981), and pendimethalin (Pre-M). The latter severely inhibits St. Augustinegrass roots (McCarty et al., 1995b) but is less harmful to bermudagrass roots than dithiopyr (Dimension) or prodiamine (Barricade) (Fishel and Coats, 1993). Pronamide (Kerb) is used for control of annual bluegrass in overseeded golf course greens (Reilly, 1971). Dithiopyr has been developed more recently; it has some postemergence efficacy, but has reportedly yielded inconsistent results on annual bluegrass. Bensulide (Betasan, etc.) was previously more widely used for preemergent weed control, but has largely been replaced by other products. These compounds have generally replaced the dinitroaniline compounds such benefin (Balan) developed in the 1960's. There have been many reports of goosegrass resistance to dinitroanilines (e.g., Mudge et al., 1984). Another fairly recent preemergence herbicide is metolachlor (Pennant), which does affect St. Augustinegrass sod regrowth (McCarty et al., 1995a), but is effective in controlling some sedges and red sprangletop. Isoxaben (Gallery) is useful against broadleafs, and has no rooting effect on St. Augustinegrass (McCarty et al., 1995a). Other herbicides have been developed for special situations in turfgrass: methyl bromide for preplant fumigation; paraquat (Evers, 1977; Johnson, 1983), glyphosate (Roundup) (Burt, 1980; Johnson and Ware, 1978; Murdoch and Nishimoto, 1974; and Whitwell and Santelman, 1978), and imazapyr (Arsenal) (Griffin et al., 1994) for edging and turfgrass renovation; ethofumesate (Prograss) + atrazine for common bermudagrass, Cynodon dactylon (L.) Pers., control in St. Augustinegrass (McCarty, 1996); and quinclorac (Facet, Drive) + MSMA in split applications for torpedograss control in bermudagrass (McCarty et al., 1993). There is considerable concern that the scheduled phaseout of methyl bromide by the year 2001 will disrupt the quality of turfgrass vegetative planting stock. This could be quite critical unless alternative strategies are developed for preplant weed control, specifically to cover the problem of off-type bermudagrass. Steam sterilization and other unconventional approaches should be investigated for greens reconstruction. The dynamics of bermudagrass infestation should also be investigated. The method of procedure would be to artificially contaminate experimental golf course greens, and then measure the rate of expansion and the probability of detection for off-types. This fundamental work would strongly support (but not guarantee) the maintenance of contamination-free bermudagrass greens. The use of turfgrass herbicides in mixed landscape communities is a challenge, because desirable broadleaf species such as oak trees (Quercus spp.) are sometimes damaged by grass herbicides, e.g., hexazinone (Velpar). The availability of present turf herbicides cannot be assumed for the future. Continued registration of several important herbicides such as atrazine and members of the auxin growth regulator (e.g., 2,4-D) and arsenical (e.g., MSMA) families is in doubt (Johnson and Murphy, 1993). Concerns about leaching and human carcinogenesis exist for several herbicides. The Environmental Protection Administration has prohibited all methyl bromide production after the year 2000, due to its effect in depleting ozone. Other herbicides useful in turfgrass, such as metsulfuron-methyl (Escort, DMC), asulam (Asulox), and atrazine, have recently had restrictive changes in labeling and/or manufacturer support. References Bingham, S. W. and R. L. Shaver. 1981. Goosegrass (Eleusine indica) control during bermudagrass (Cynodon dactylon) establishment. Weed Science 29:11-16. Burt, E. O. 1980. Glyphosate for torpedograss and bermudagrass control. pp. 257-262 In: Beard, J. B. (ed.). Proceedings of the Third International Turfgrass Research Conference, Munich, West Germany. 11 Jul. 1977. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, and the International Turfgrass Society. Madison, WI. Coats, G. E., R. F. Munoz, D. H. Anderson, D. C. Heering, and J. W. Scruggs. 1987. Purple nutsedge (Cyperus rotundus) control with imazaquin in warm-season turfgrasses. Weed Science 35:691-694. Dernoeden, P. H. 1989. Bermudagrass suppression and zoysiagrass tolerance to fenoxaprop. pp. 285-290 In: Takatoh, H. (ed.). Proceedings of the Sixth International Turfgrass Research Conference, Tokyo, Japan. 31 Jul. 1989. International Turfgrass Society and the Japanese Society of Turfgrass Science. Tokyo, Japan. Evers, G. W. 1977. Use of paraquat in establishing dallisgrass and bahiagrass. Agron. J. 69:505-508. McCarty, L. B. 1996. Selective control of common bermudagrass in St. Augustinegrass. Crop Sci. 36:694-698. Fermanian, T. W., W. W. Huffine, and R. D. Morrison. 1980. Preemergence weed control in seeded bermudagrass stands. Agron. J. 72:803-805. Fishel, F. M. and G. E. Coats. 1993. Effect of commonly used turfgrass herbicides on bermudagrass (Cynodon dactylon) root growth. Weed Science 41:641-647. Griffin, K. A., R. Dickens, and M. S. West. 1994. Imazapyr for common bermudagrass control in sod fields. Crop Sci. 34:202-207. Hansen, A. A. 1921. The use of chemical weed killers on golf courses. United States Golf Association Bull. 1:128-131. Jackson, N. E., T. E. Duff, J. N. Travers, and J. M. Goette. 1993. Control of purple and yellow nutsedge in turfgrass with MON 12000. International Turfgrass Society Research Journal 7:269-272. Johnson, B. J. 1975a. Postemergence control of large crabgrass and goosegrass in turf. Weed Science 23:404-409. Johnson, B. J. 1975b. Purple nutsedge control with bentazon and perfluidone in turfgrasses. Weed Science 23:349-353. Johnson, B. J. 1980. Postemergence winter weed control in bermudagrass (Cynodon dactylon) turf. Weed Science 28:385-392. Johnson, B. J. 1983. Effects of edging herbicide treatments on bermudagrass (Cynodon dactylon) and woody ornamentals. Weed Science 31:707-711. J Johnson, B. J. 1992. Common bermudagrass (Cynodon dactylon) suppression in Zoysia spp. with herbicides. Weed Technology 6:813-819. Johnson, B. J. and T. R. Murphy. 1993. Current status of warm-season turfgrass weed control and future directions. International Turfgrass Society Research Journal 7:58-68. Johnson, B. J. and G. O. Ware. 1978. Dates of glyphosate treatments on weeds and bermudagrass (Cynodon dactylon). Weed Science 26:523-526. McCarty, L. B. 1991. Goosegrass (Eleusine indica) control in bermudagrass (Cynodon spp.) turf with diclofop. Weed Science 39:255-261. McCarty, L. B., J. M. Higgins, and D. L. Colvin. 1993. Selective torpedograss (Panicum repens) control in bermudagrass (Cynodon spp) turf. Weed Technology 7:911-915. McCarty, L. B., L. C. Miller, and D. L. Colvin. 1991. Bermudagrass (Cynodon spp.) cultivar response to diclofop, MSMA and metribuzin. Weed Technology 5:27-32. McCarty, L. B., D. W. Porter, and D. L. Colvin. 1995a. Sod regrowth of St. Augustinegrass after preemergence herbicide application. Agron. J. 87:503-507. McCarty, L. B., D. W. Porter, D. L. Colvin, D. G. Shilling, and D. W. Hall. 1995b. St. Augustinegrass rooting following preemergence herbicide application. J. Am. Soc. Hort. Sci. 120:374-378. Mudge, L. C., B. J. Gossett, and T. R. Murphy. 1984. Resistance of goosegrass (Eleusine indica) to dinitroaniline herbicides. Weed Sci. 32:591-594. Murdoch, C. L. and R. K. Nishimoto. 1974. Use of glyphosate (N-phosphonomethyl glycine) for edging and controlling weeds in golf course sand traps. HortScience 9:32. Murdoch, C. L. and R. K. Nishimoto. 1982. Diclofop for goosegrass control in bermudagrass putting greens. HortScience 17:914-915. Neel, P. L., E. O. Burt, and S. L. Carlyle. 1979. Tolerance of 5 warm-season turfgrasses and 36 ornamental plant species to asulam. Journal of the American Society for Horticultural Science 104:129-132. Reilly, D. 1971. Control of winter grass in Cynodon dactylon (L.) P turf in New South Wales with pronamide. Journal of the Sports Turf Research Institute 47:26-32. White, R. W. and P. Busey. 1987. History of turfgrass production in Florida. Proceedings of the Florida State Horticultural Society 100:167-174. Whitwell, T. and P. W. Santelmann. 1978. Influence of growth stage and
soil conditions on bermudagrass susceptibility to glyphosate. Agron. J. 70:653-656. 27 October 1998 |
Postemergence control of sedges had long presented an unsolved problem. MSMA
was marginally effective. By the 1970's, bentazon (Basagran, etc.) was shown (Johnson,
1975b) to control sedges (Cyperus spp.), and by the 1980's, imazaquin (Image) became
available for control of purple nutsedge (Coats et al., 1987). In the early 1990's,
halosulfuron-methyl (Manage) was shown to have efficacy against both annual sedges and
purple nutsedge (Jackson et al., 1993).