" Buffalograss Tolerance to Postemergence Herbicides"

HORTSCIENCE 27(8):898-899. 1992. bicides for grass, broadleaf, and sedge weed control. Experiments were conducted near Braden- Buffalograss Tolerance to ton, Fla., at a commercial sod production farm on a Myakka fine sand (sandy, sili- Postemergence Herbicides ceous, hyperthermic Typic Psammaquets). Buffalograss was maintained at a moderate Lambert B. McCarty and Daniel L. Colvin to high maintenance level with a mowing Department of Environmental Horticulture, University of Florida, height of 3.8 cm, N (sources varied) appli- -1 Institute of Food and Agricultural Sciences, Fifield Hall, Box 110670, cations of 49 kg·ha every 6 to 8 weeks, Gainesville, FL 32611-0670 and irrigation to prevent drought stress. Ma- ture ‘Prairie’ and ‘Oasis’ buffalograss were Additional index words. Buchloe dactyloides, turf, weed control subjected to the herbicide treatments listed in Table 1. Experiments involving the two Abstract. Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a turfgrass species cultivars were initiated in June 1991, and the traditionally adapted to low-rainfall areas that may incur unacceptable weed encroach- test was repeated in Aug. 1991 on an adja- ment when grown in higher rainfall areas such as Florida. An experiment was per- cent site. Herbicides were applied with a CO2- formed to evaluate the tolerance of two new buffalograss cultivars, ‘Oasis’ and ‘Prairie’, powered backpack sprayer calibrated to de- to postemergence herbicides commonly used for grass, broadleaf, and sedge weed liver 187 liters·ha-1. Crop-oil concentrate was control. Twenty to 40 days were required for each cultivar to recover from treatment added at 1.25% (v/v) to all treatments, ex- with asulam, MSMA, and sethoxydim (2.24, 2.24, and 0.56 kg-ha-l, respectively). cept for those commercial formulations with Other herbicides used for postemergence grass weed control (metsulfuron, quinclorac, -1 premixed oil. Plots measuring 3 x 3 m were and diclofop at 0.017, 0.56, and 1.12 kg·ha , respectively) did not cause unacceptable arranged in a randomized complete-block buffalograss injury. Herbicides used for postemergence broadleaf weed control, triclo- -1 design with four replicates. pyr, 2,4-D, sulfometuron, dicamba (0.56, 1.12, 0.017, and 0.56 kg·ha , respectively), Buffalograss quality following application and a three-way combination of 2,4-D + dicamba + mecoprop (1.2 + 0.54 + 0.13 -1 of herbicides was assessed visually using a kg·ha ), caused 20 to 30 days of unacceptable or marginally acceptable turfgrass 1 to 9 scale, where best turf was rated 9 and quality, while 20 days were required for ‘Prairie’ buffalograss to recover from atrazine 6.5 was considered the minimum acceptable treatments. ‘Oasis’ buffalograss did not fully recover from 2,4-D or 2,4-D + dicamba turf quality level in terms of turf color, shoot + mecoprop through 40 days after treatment. Herbicides used for postemergence sedge density, and uniformity. Data were subjected control, bentazon and imazaquin, caused slightly reduced, but acceptable, levels of to analysis of variance to test for interactions turf quality in both cultivars throughout the experiment. Chemical names used: 6- within and between experiments, cultivars, chloro-N-ethyl-N’-(1-methylethyl)-1,3,5-triazine-2,4-diamine (atrazine); methyl[(4- and herbicide treatments. Treatment means aminophenyl)sulfonyl]carhamate (asulam); 3-(1-methylethyl)-(1H)-2,1,3-benzothiadi- were separated by Waller-Duncan’s k = 100 azin-4(3H)-one 2,2-dioxide (bentazon); 3,6-dichloro-2-methoxybenzoic acid (dicamba); t test at P = 0.05. (±)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid (diclofop); 2-[4,5-dihydro-4- Cultivar interactions were significant; methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imaza- however, experiment interactions were not. quin); (±)-2-(4-chloro-2-methylphenoxy)propanoic acid (mecoprop); 2-[[[[(4-methoxy- Therefore, data were separated by cultivar 6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]benzoic acid (metsulfuron); and combined over experiments. monosodium salt of methylarsonic acid (MSMA); 2-[1-(ethoxyimino)butyl]-5-[2-(ethyl- ‘Oasis’. Unacceptable turf quality 10 days thio)propyl]-3-hydroxy-2-cyclohexen-1-one(sethoxydim); 2-[[[[(4,6-dimethylethyl-2- after treatment (DAT) followed application pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid (sulfometuron); [(3,5,6-trich- of asulam, dicamba, sethoxydim, sulfome- loro-2-pyridinyl)oxy]acetic acid (triclopyr); (2,4-dichlorophenoxyl)acetic acid (2,4-D); turon, triclopyr, 2,4-D, and the three-way 3,7-dichloro-8-quinolinecarboxylic acid (quinclorac). combination of 2,4-D + dicamba + mecoprop (Table 1). Turf was unaffected at this Buffalograss is a warm-season, stolon- when buffalograss is maintained under man- time by bentazon, diclofop, and metsulfuron iferous turfgrass native to the Great Plains agement regimes that are more intense than treatments. Turf quality at 20 DAT was ac- of North America from Montana to Mexico the natural adaptation of the grass, problems ceptable for all treatments, except sethoxy- (Duble, 1989). Desirable buffalograss char- may occur (Duble, 1989; Riordan, 1991). If dim, sulfometuron, triclopyr, and 2,4-D + acteristics include excellent drought resis- buffalograss is overwatered, overfertilized, dicamba + mecoprop. Asulam- and 2,4-D- tance and the ability to produce acceptable or exposed to excessive traffic, stand density treated turf was marginally (6.5-6.9) ac- turf in subhumid and semiarid regions that and vigor are often reduced, leading to open ceptable at 20 DAT. Turfgrass quality at 30 received an average annual rainfall of 300 to niches where weeds can easily become es- DAT was acceptable for all treatments, ex- 560 mm. These characteristics have created tablished. Currently, extensive breeding ef- cept for 2,4-D and 2,4-D + dicamba + me- interest in the possibility of growing buffa- forts are concentrated on producing improved coprop. Although acceptable, triclopyr-treated lograss outside its native habitat, in areas varieties that tolerate intensive maintenance turf exhibited marginal phytotoxicity at 30 that are facing increasing water shortages. A practices and much traffic. ‘Prairie’ and ‘Oa- DAT. At 40 DAT, buffalograss had re- low water-requiring and aesthetically ac- sis’ are two recently released buffalograss covered to acceptable levels, except for those ceptable turfgrass would be ideal for low- cultivars that exhibit improved turf quality, plots treated with 2,4-D and 2,4-D + di- maintenance areas such as roadsides, golf recuperative potential, and extended fall camba + mecoprop. course roughs, utility rights-of-way, and greenness (Riordan, 1991). These cultivars ‘Prairie’. Buffalograss quality 10 DAT was playgrounds. likely will be used successfully outside the reduced, relative to the control, by all treat- Researchers, however, have noted that Great Plains in states east of the Mississippi ments except the bentazon, imazaquin, met- River. To our knowledge, no research has sulfuron, and quinclorac treatments (Table been conducted on buffalograss concerning 1). At 10 DAT, turf quality was unaccept- its tolerance to postemergence herbicides. able for plots treated with 2,4-D, asulam, Received for publication 13 Dec. 1991. Accepted Given the possibility of buffalograss having atrazine, dicamba, MSMA, sethoxydim, for publication 27 Mar. 1992. Florida Agr. Expt. greater weed invasion problems when grown sulfometuron, and 2,4-D + dicamba + me- Sta. J. series no. R-02045. The cost of publishing this paper was defrayed in part by the payment of outside the Great Plains, research was con- coprop. At 20 DAT, unacceptable turf qual- page charges. Under postal regulations, this paper ducted at the Univ. of Florida to determine ity was present on plots treated with asulam, therefore must be hereby marked advertisement the tolerance of ‘Prairie’ and ‘Oasis’ buffa- sethoxydim, and sulfometuron, with only solely to indicate this fact. lograss to currently used postemergence her- marginal quality exhibited by turf treated with HORTSCIENCE, VOL. 27(8), AUGUST 1992 Table 1. Quality rating of ‘Oasis’ and ‘Prairie’ buffalograss at given day after treatment (DAT) with selected herbicides. zRated visually on a scale of 1 to 9, where 9 = best turf and 6.5 = minimum acceptability. yMSD = minimum significant difference according to the Waller-Duncan k ratio t test; data are the means of two separate experiments with four observations per experiment. triclopyr, 2,4-D, dicamba, and 2,4-D + di- 2.2, and 4.5 kg·ha-1) to mature buffalograss Treatment with other herbicides used for camba + mecoprop. None of the other treat- reduced turf quality through 40 DAT. Buf- postemergence broadleaf and sedge weed ments had reduced turf quality at an unac- falograss treated with high rates of these her- control (atrazine, imazaquin, and bentazon) ceptable level 20 DAT. Turf quality 30 DAT bicides did not recover through 70 days. did not reduce turf quality to an unacceptable was acceptable for all treatments except se- In this study, herbicides used for post- level throughout the experiments with either thoxydim. By 40 DAT, buffalograss quality emergence grass weed control (MSMA, asu- cultivar. Both of them exhibited acceptable was acceptable for all treatments. Herbicide lam, and sethoxydim) induced initial moderate tolerance to metsulfuron and quinclorac, two treatments providing ratings similar to the to severe damage on ‘Prairie’ and ‘Oasis’ relatively new herbicides with postemergence untreated

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