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Aaron J. Patton, David W. Williams, and Zachary J. Reicher

Zoysiagrass (Zoysia japonica Steud.) requires few inputs and provides high-quality turf in the transition zone, but is expensive to sprig or sod. Establishment by seed is less expensive than vegetative establishment, but little is known about renovation of existing turf to zoysiagrass using seed. Two experiments were performed to determine effects of herbicides and seeding rates on establishment of zoysiagrass in Indiana and Kentucky. In the first experiment, interseeding zoysiagrass into existing perennial ryegrass (Lolium perenne L.) without the use of glyphosate before seeding resulted in 2% zoysiagrass coverage 120 days after seeding (DAS). In plots receiving glyphosate before seeding, zoysiagrass coverage reached 100% by 120 DAS. In the second experiment, MSMA + dithiopyr applied 14 days after emergence (DAE) or MSMA applied at 14+28+42 DAE provided the best control of annual grassy weeds and the greatest amount of zoysiagrass establishment. Applying MSMA + dithiopyr 14 DAE provided 7% less zoysiagrass coverage compared to MSMA applied 14 DAE at one of the four locations. Increasing the seeding rate from 49 kg·ha-1 to 98 kg·ha-1 provided 3% to 11% more zoysiagrass coverage by the end of the growing season at 3 of 4 locations. Successful zoysiagrass establishment in the transition zone is most dependent on adequate control of existing turf using glyphosate before seeding and applications of MSMA at 14+28+42 DAE, but establishment is only marginally dependent on seeding rates greater than 49 kg·ha-1. Chemical names used: N-(phosphonomethyl) glycine (glyphosate); monosodium methanearsenate (MSMA); S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(triflurormethyl)-3,5-pyridinedicarbothioate (dithiopyr).

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B. Jack Johnson

Three field experiments were conducted to determine if several preemergence and postemergence herbicides were safe to apply to creeping bentgrass (Agrostis stolonifera L. `Penncross') maintained at putting green height. When dithiopyr was applied at preemergence in late February or early March, the emulsifiable concentrate formulation (≤1.7 kg·ha-1) and granular formulation (≤1.1 kg·ha-1) did not reduce the quality or cover of creeping bentgrass. Applied at preemergence, bensulide plus oxadiazon at 6.7 + 1.7 kg·ha-1 and 13.4 + 3.4 kg·ha-1 reduced turfgrass quality for 2 to 3 weeks and 8 weeks after treatment, respectively. When MON 12051 and monosodium salt of methylarsonic acid (MSMA) (≤0.14 and ≤2.2 kg·ha-1, respectively) were applied at postemergence to creeping bentgrass in early June, the reduction in turfgrass quality varied from slight to moderate for 1 to 2 weeks, but turfgrass fully recovered with no effect on turfgrass cover. Quinclorac applied at postemergence in early June at ≥0.6 kg·ha-1 severely reduced creeping bentgrass quality and cover for ≥8 weeks. Diclofop at 0.6 kg·ha-1 applied to creeping bentgrass in June, July, or August maintained consistently higher quality and cover ratings than when applied at ≥1.1 kg·ha-1. Diclofop applied at 0.6 kg·ha-1 in June and repeated at the same rate in July reduced quality of creeping bentgrass less than when applied at 1.1 kg·ha-1 at any date. Chemical names used: O,O-bis (1-methylethyl) S-{2-[(phenylsulfonyl)amino]ethyl} phosphorodithioate (bensulide); (±)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid (diclofop); S,S-dimethyl-2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate (dithiopyr); methyl-5-{[(4,6-dimethoxy-2-pyrimidinyl)amino] carbonylaminosulfonyl}-3-chloro-1-methyl-1-H-pyrazol-4-carboxylate (MON 12051); 3-[2,4-dicloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); 3,7-dicloro-8-quinolinecarboxylic acid (quinclorac).

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Robert Andrew Kerr, Lambert B. McCarty, Philip J. Brown, James Harris, and J. Scott McElroy

, reduced performance by certain herbicides (e.g., foramsulfuron), cancellation of goosegrass-specific herbicides (e.g., diclofop-methyl), and cancellation and/or severe use reductions of other herbicides (e.g., MSMA) have limited the options end users have

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B. Jack Johnson

Low rates of preemergence herbicides were applied with postemergence herbicides as sequential applications or as tank-mixed applications for large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass [Eleusine indica (L.) Gaertn.] control in Kentucky bluegrass (Poa pratensis L.). In 1991, a higher percentage of large crabgrass control (83%) was obtained in late August from sequential applications of oxadiazon at 2.2 kg·ha-1 applied in early March and followed by fenoxaprop at 0.20 kg·ha-1 in June than when oxadiazon (62%) or fenoxaprop (11%) was applied alone. During this period, sequential applications of oxadiazon at 2.2 kg·ha-1 and monosodium salt of MAA (MSMA) at 2.2 kg·ha-1 achieved 79% control of large crabgrass, while the control was at ≤46% when MSMA or fenoxaprop was applied to plots previously treated with pendimethalin at 1.7 kg·ha-1 or dithiopyr at 0.28 kg·ha-1. There was no advantage from sequential applications of preemergence and postemergence herbicides for large crabgrass control in 1992, when compared with postemergence herbicides applied alone. Large crabgrass control in late August was higher over 2 years from tank-mixes of pendimethalin at 1.7 kg·ha-1 with fenoxaprop at 0.14 kg·ha-1 (80%) than when pendimethalin (28%) or fenoxaprop (55%) was applied alone at the same rates. The control was also higher from tank-mixes of pendimethalin at 1.7 kg·ha-1 with MSMA at 2.2 kg·ha-1 (92%), when compared with MSMA (77%) alone. The response was similar from tank-mixes of dithiopyr at 0.28 kg·ha-1 with fenoxaprop at 0.14 kg·ha-1 (98%) or with MSMA at 2.2 kg·ha-1 (98%), when compared with dithiopyr applied alone (81%) at the same rate. Quinclorac applied alone at 0.84 kg·ha-1 controlled large crabgrass as effectively as when applied to plots previously treated with preemergence herbicides or when applied tank-mixed with preemergence herbicides. None of the preemergence herbicides applied at low rates with postemergence herbicides (fenoxaprop, MSMA, or quinclorac) controlled goosegrass. Chemical names used: S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate (dithiopyr); (±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]-phenoxy]propanoic acid (fenoxaprop); 3-[2,4-dichloro-5-(1-methylethoxy)-phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzen-amine (pendimethalin); and 3,7-dichloro-8-quinoline-carboxylic acid (quinclorac).

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E.T. Pippin, E.W. Bush, D.J. Lee, and R.E. Strahan

Weeping lovegrass (Eragrostis curvula) is commonly used in native areas bordering golf courses in the Southeastern United States. These areas do not receive significant levels of maintenance, thus weed encroachment is a problem that can negatively impact the functional and aesthetic values of the golf course. The objectives of this study is to determine which selective postemergent herbicides labeled for use on golf courses can remove weeds from Weeping Lovegrass and to determine the level of phytotoxicity. Herbicides included monosodium methane arsenate (MSMA 6.0) applied at 3.0 lb/acre a.i., sulfosulfuron (Certainty) at 0.047 lb/acre a.i., metribuzin (Sencor 75 DF) at 0.5 lb/acre a.i., and imazaquin (Image 70 DG) at a rate of 0.5 lb/acre a.i.. Treatments were applied on July 20, 2004 to 9.6 × 9.6 plots arranged in a randomized complete block design (RCBD) using Teejet 8005 nozzles at 40 psi calibrated to deliver 40 ga/acre. Plots were monitored daily and data was collected 0, 7, 14, 21, 28, 35, and 42 DAT. Sulfosulfuron and MSMA provided the highest level of weed control 35 DAT. Metribuzin and imazaquin provided limited weed suppression compared to the control. Initial phytotoxic damage to the Lovegrass was observed in all herbicide treatments. The highest level of phytotoxic damage was observed in the MSMA and Metribuzin treatments; however there was no apparent damage at 42 DAT. Herbicide applications of sulfosulfuron and MSMA are effective in reducing weed populations with acceptable levels of phytotoxicity to the Lovegrass.

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Billy J. Johnson, Robert N. Carrow, and Tim R. Murphy

Field experiments were conducted to determine the effects of foliar iron (Fe) applied with postemergence herbicides on injury, color, and quality of `Tifway' bermudagrass [Cynodon transvaalensis Burtt-Davy × Cynodon dactylon (L.) Pers.]. Iron significantly decreased injury and improved quality and color of `Tifway' bermudagrass in conjunction with herbicide treatment. Turf injury was less for 4 to 18 days after the initial MSMA application when Fe was added. Injury was also less from sequential Fe treatment with MSMA + metribuzin (up to 4 days) and MSMA + imazaquin (from 4 to 10 days) compared to the respective herbicides applied alone. There was no difference in turf injury from Fe when imazaquin at 1.3 kg·ha-1 was applied as a single treatment. However, turf treated with Fe and two applications of imazaquin (9- to 10-day interval) recovered from herbicide injury faster than when treated only with the herbicide. Iron did not prevent immediate 2,4-D + mecoprop + dicamba injury to the bermudagrass, but did hasten turf recovery from injury at 26 days after treatment. With a few exceptions, `Tifway' bermudagrass quality was higher and color improved when Fe was added. However, injury expressed as loss of shoot density was not affected by Fe and only injury expressed as color loss was improved by Fe. Chemical names used: 3,6-dichloro-2-methoxybenzoic acid (dicamba), 2-[4,5-dihydro-4-methyl)-4-(1-methylethyl)-5-oxo-1H-imidazol-2yl]-3-quinolinecarboxylic acid (imazaquin), (±)-2-(4-chloro-2-methylphenoxy)propanoic acid (mecoprop), 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one (metribuzin), monosodium salt of MAA (MSMA), and (2,4-dichlorophenoxy)acetic acid (2,4-D).

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A. James Downer, D.W. Cudney, M. Henry, V. Gibeault, and S. Cockerham

Kikuyugrass (Pennisetum clandestinum Hochst.) an aggressive weed of cool season turfgrass in coastal California, Spreads rapidly by growth of robust stolons and seedlings. Kikuyugrass competition was studied by placing plugs of six turfgrasses in a kikuyugrass sward. Plug diameters increased when triclopyr (.56kg ai/ha) or quinclorac (.74kg ai/hg) were repeatedly applied (4 times) in combination with MSMA (2.2kg ai/ha). These herbicide combinations also eradicated kikuyugrass in lawns of cool season turfgrass. Kikuyugrass density was reduced from 75% of the turfgrass sward to 0%. Resurgence of kikuyugrass has not exceeded 5% 4 months posttreatment.

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Bielinski M. Santos and Jose P. Morales-Payan

Trials were conducted under controlled conditions to determine the tolerance of young papaya plants (15 cm tall) to postemergence herbicides. Herbicides used were paraquat (1.68 Kg ai/Ha), MSMA (2.24 Kg ai/Ha), 2,4-D (4.26 Kg ai/Ha), bromoxynil (0.28 Kg ai/Ha), cyanazine (1.12 Kg ai/Ha), dimethenamid (1.12 Kg ai/Ha), endothal (0.56 Kg ai/Ha), imazameth (0.067 Kg ai/Ha), imazethapyr (0.028 Kg ai/Ha) lactofen (0.12 Kg ai/Ha), oxyfluorfen (0.03 Kg ai/Ha), acifluorfen (0.28 Kg ai/Ha), atrazine (2.24 Kg ai/Ha), and bentazon (1.12 Kg ai/Ha) as well as the untreated control. Atrazine, bentazon, cyanazine, imazemeth, imazethapyr, and dimethenamid did not cause phytotoxicity at the rates used and were equal to the untreated control. Other herbicides caused severe injuries followed by total death at 10 days after treatment.

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Jack D. Fry and Ward S. Upham

In 1992 and 1993, 12 postemergence herbicide treatments were applied to field-grown buffalograss [Buchloe dactyloides (Nutt.) Engelm.] seedlings having 1 to 3 leaves and 2 to 4 tillers, respectively. The only herbicide treatments that did not cause plant injury at 1 or 2 weeks after treatment (WAT) or reduce turf coverage 4 or 6 WAT compared to nontreated plots (in 1992 or 1993) were (in kg·ha–1) 0.6 dithiopyr, 0.8 quinclorac, 2.2 MSMA, and 0.8 clorpyralid. Evaluated only in 1993, metsulfuron methyl (0.04 kg·ha–1) also caused no plant injury or reduction in coverage. Fenoxaprop-ethyl (0.2 kg·ha–1) caused severe plant injury and reduced coverage by >95% at 6 WAT. Dicamba reduced coverage by 11% at 6 WAT in 1992 but not 1993. The chemicals (in kg·ha–1) triclopyr (0.6), 2,4-D (0.8), triclopyr (1.1) + 2,4-D (2.8), 2,4-D (3.1) + triclopyr (0.3) + clorpyralid (0.2), and 2,4-D (2.0) + mecoprop (1.1) + dicamba (0.2) caused plant injury at 1 or 2 WAT in 1992 or 1993, but coverage was similar to that of nontreated turf by 6 WAT. Chemical names used: 3,6-dichloro-2-pyridinecarboxylic acid (clorpyralid); 3,6-dichloro-o-anisic acid (dicamba); (+/–)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid (diclofop); 3,5-pyridinedicarbothioic acid, 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-S,S-dimethyl ester (dithiopyr); 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy] propanoate (fenoxaprop-ethyl); 2-(2,4-dichlorophenoxy)propionic acid (mecoprop); methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-amino]carbonyl]amino]sulfonyl]benzoate (metsulfuron methyl); monosodium salt of methylarsonic acid (MSMA); 3,7-dichloro-8-quinolinecarboxylic acid (quinclorac); [(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid (triclopyr); (2,4-dichlorophenoxy) acetic acid (2,4-D).

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Lambert B. McCarty and Daniel L. Colvin

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a turfgrass species traditionally adapted to low-rainfall areas that may incur unacceptable weed encroachment when grown in higher rainfall areas such as Florida. An experiment was performed to evaluate the tolerance of two new buffalograss cultivars, `Oasis' and `Prairie', to postemergence herbicides commonly used for grass, broadleaf, and sedge weed control. Twenty to 40 days were required for each cultivar to recover from treatment with asulam, MSMA, and sethoxydim (2.24, 2.24, and 0.56 kg-ha-l, respectively). Other herbicides used for postemergence grass weed control (metsulfuron, quinclorac, and diclofop at 0.017, 0.56, and 1.12 kg·ha-1, respectively) did not cause unacceptable buffalograss injury. Herbicides used for postemergence broadleaf weed control, triclopyr, 2,4-D, sulfometuron, dicamba (0.56, 1.12, 0.017, and 0.56 kg·ha-1, respectively), and a three-way combination of 2,4-D + dicamba + mecoprop (1.2 + 0.54 + 0.13 kg·ha-1), caused 20 to 30 days of unacceptable or marginally acceptable turfgrass quality, while 20 days were required for `Prairie' buffalograss to recover from atrazine treatments. `Oasis' buffalograss did not fully recover from 2,4-D or 2,4-D + dicamba + mecoprop through 40 days after treatment. Herbicides used for postemergence sedge control, bentazon and imazaquin, caused slightly reduced, but acceptable, levels of turf quality in both cultivars throughout the experiment. Chemical names used: 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine (atrazine); methyl[(4-aminophenyl)sulfonyl]carhamate (asulam); 3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (bentazon); 3,6-dichloro-2-methoxybenzoic acid (dicamba); (±)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid (diclofop); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imazaquin); (±)-2-(4-chloro-2-methylphenoxy)propanoic acid (mecoprop); 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]benzoic acid (metsulfuron); monosodium salt of methylarsonic acid (MSMA); 2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one(sethoxydim); 2-[[[[(4,6-dimethylethyl-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid (sulfometuron); [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr); (2,4-dichlorophenoxyl)acetic acid (2,4-D); 3,7-dichloro-8-quinolinecarboxylic acid (quinclorac).