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Ethan T. Parker, J. Scott McElroy, and Michael L. Flessner

Smooth crabgrass and goosegrass are problematic weeds in creeping bentgrass in the transition zone, an area that rests between the southern United States where warm-season grasses dominate, and the northern United States where cool-season grasses

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James T. Brosnan, Gregory K. Breeden, and Patrick E. McCullough

Smooth crabgrass [ Digitaria ischaemum (Schreb) Schreb. ex Muhl.] infestations are common in golf course, athletic field, and landscape turf ( McCarty et al., 2005 ). Smooth crabgrass is similar to large crabgrass ( Digitaria sanguinalis L. Scop

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P.H. Demoeden, M.J. Mahoney, and M.J. Carroll

Fenoxaprop (0.027, 0.036, and 0.045 kg·ha-1) was field-applied at either of 2-, 3-, or 4-week intervals to perennial ryegrass (Lolium perenne L.) naturally infested with smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl.] in Maryland (Easton and Silver Spring) during 1989 and 1990. In 1989, fenoxaprop applied at 2- or 3-week intervals at 0.027 kg·ha-1 provided fair (>74%) to good (>80%) smooth crabgrass control. Fenoxaprop applied at 0.036 or 0.045 kg·ha-1 at 2- or 3week intervals provided good to excellent (> 90%) smooth crabgrass control. Four-week intervals generally provided control that was inferior to the shorter application intervals at Silver Spring but not at Easton. In 1990, all rates provided good to excellent smooth crabgrass control when applied at 2- or 3-week intervals in Easton. At Silver Spring, where smooth crabgrass levels were very high, >88% control was provided by 0.036 kg·ha-1 applied at a 2-week interval and by 0.045 kg·ha-1 applied at either a 2- or 3-week interval. Chemical name used: [±]-2-[4-[(6 chloro-2 benzoxazolyl)oxy]phenoxy] propanoic acid (fenoxaprop).

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Peter H. Dernoeden, Cale A. Bigelow, John E. Kaminski, and John M. Krouse

Smooth crabgrass [Digitaria ischaemum (Schreber) Schreber ex Muhlenb.] is an invasive weed of cool-season turfgrasses. Previous research has demonstrated that quinclorac is an effective postemergence herbicide for crabgrass control, but performance has been erratic in some regions. Furthermore, quinclorac may elicit objectionable levels of discoloration in creeping bentgrass (Agrostis stolonifera L.). The objectives of this 3-year field study were to determine optimum rates and timings of quinclorac applications that provide consistent levels of effective crabgrass control and to assess creeping bentgrass quality responses to quinclorac. To evaluate crabgrass control, quinclorac was applied in early-, mid- and late-postemergence timings at various rates to a perennial ryegrass (Lolium perenne L.) turf. Similar treatments were applied to creeping bentgrass to determine if application timing and rate influenced the level and duration of discoloration. Quinclorac was applied alone or was tank-mixed with either urea (N at 6.1 kg·ha-1) or chelated iron (Fe)+nitrogen (N) (FeSO4 at 1.1 kg·ha-1+N at 2.2 kg·ha-1) to determine if they would mask discoloration. Crabgrass control generally was more effective in the early- and midpostemergence application timings. A single application of quinclorac (0.84 kg·ha-1) was effective where crabgrass levels were moderate, but sequential (i.e. multiple) applications were required where crabgrass levels were severe. The most consistent level of crabgrass control where weed pressure was severe occurred with three, sequential quinclorac (0.37 or 0.42 kg·ha-1) applications. Creeping bentgrass exhibited 2 to 11 weeks of unacceptable discoloration in response to sequential quinclorac applications. Chelated Fe+N was more effective than urea in masking discoloration. In general, chelated Fe+N tank-mixed with quinclorac masked discoloration and turf had quality equivalent to untreated bentgrass on most, but not all rating dates. Chemical names used: 3,7,-dichloro-8-quinolinecarboxylic acid (quinclorac).

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Kenneth Cropper, Gregg Munshaw, and Michael Barrett

Smooth crabgrass ( Digitaria ischaemum ) is a common summer annual weed found throughout much of the United States. Its long leaves and prostrate growth give it the potential to become a serious problem in both closely mowed areas such as greens or

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Charles L. Webber III, Merritt J. Taylor, and James W. Shrefler

initial applications, smooth crabgrass was 8 to 15 cm tall, cutleaf groundcherry was 5 to 8 cm tall, and spiny amaranth was 5 to 8 cm tall. Smooth crabgrass represented 60% of the weed cover, whereas cutleaf groundcherry and spiny amaranth represented 36

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Charles L. Webber III, Merritt J. Taylor, and James W. Shrefler

applications. At the time of initial applications, smooth crabgrass was 8 to 10 cm tall, cutleaf groundcherry was 5 cm tall, spiny amaranth was 8 to 10 cm tall, and yellow nutsedge was 10 to 15 cm tall. Smooth crabgrass represented 60% of the weed cover, while

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M.J. Carroll, P.H. Dernoeden, and J.M. Krouse

Sprigs of `Meyer' zoysiagrass (Zoysia japonica Steud.) were treated with urea nitrogen, a biostimulator, and one of three preemergence herbicides or one of two postemergence herbicides to hasten establishment in two field studies. Monthly application of N at 48 kg·ha–1 during the growing season had no influence on sprig establishment the first year, but slightly increased (+5%) zoysiagrass cover the second year. Presoaking sprigs in a solution containing (mg·L–1) 173 auxin and 81 cytokinin, and iron at 1.25 g·L–1 before broadcasting of sprigs, and biweekly sprays (g·ha–1) of 53 auxin and 24 cytokinin, and iron at 0.2 g·L–1 or (g·ha–1) 68 auxin and 36 cytokinin, and iron at 1.45 g·L–1 after broadcasting sprigs had no effect on zoysiagrass cover or rooting. Preemergence and postemergence herbicide use generally enhanced zoysiagrass cover by reducing smooth crabgrass competition [Digitaria ischaemum (Schreb. ex Schweig) Schreb. ex Muhl]. Oxadiazon enhanced zoysiagrass coverage more than dithiopyr, pendimethalin, quinclorac, or fenoxaprop. Oxadiazon and dithiopyr provided similar levels of crabgrass control, but dithiopyr reduced `Meyer' zoysiagrass midsummer root growth. Chemical names used: 3,5,-pyridinedicarbothioic acid, 2-[difluromethyl]-4-[2-methyl-propyl]-6-(trifluoromethyl)-S,S-dimethyl ester (dithiopyr); [±]-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy] propanoate (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-dinitrobenzenamine (pendimethalin); 3,7-dichloro-8-quin-olinecarboxylic acid (quinclorac).

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Katie J. Kammler, S. Alan Walters, and Bryan G. Young

( Setaria faberi Herrm.), redroot pigweed ( Amaranthus retroflexus L.), and stinkgrass [ Eragrostis cilianensis (All.) Vign. ex Janchen], were detected at low densities compared with large and smooth crabgrass. Crabgrass species control was visually

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P.H. Dernoeden and M.A. Fidanza

Fenoxaprop is used on turfgrasses to control smooth crabgrass [Digitaria ischaemum (Schreb. ex Sweib.) Schreb. ex Muhl.] and other annual grass weeds. Our objective was to determine if a broadleaf weed herbicide (BWH = 2,4-D + mecoprop + dicamba) would affect fenoxaprop activity. The BWH was applied several days or weeks before and after fenoxaprop was applied. Smooth crabgrass control by fenoxaprop was reduced significantly when the BWH was applied ≤14 days before fenoxaprop was applied. Extremely poor crabgrass control occurred when fenoxaprop was tank-mixed with the BWH. There was no reduction in crabgrass control when the BWH was applied 21 days before or ≥3 days after fenoxaprop. Chemical names used: ethyl ester of (±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid (fenoxaprop); 2,4-dichlorophenoxy acetic acid (2,4-D); (+)-2-(4-chloro-2-methylphenoxy)propanoic acid (mecoprop); 3,6-dichloro-2-methoxybenzoic acid (dicamba).