Broadleaf Signalgrass Control Research Articles

Weed Management in Strip-tilled Irish Potato and Sweetpotato Systems

Experiments were conducted to evaluate the effect of tillage systems and weed management on weed suppression and potato yield. Strip-tillage (ST) and conventional-tillage (CT) systems produced equal yields of Irish potato (Solanum tuberosum L.) or sweetpotato [Ipomoea batatas (L.) Lam.] when herbicide treatments were applied. Weeds in the nontreated control reduced yield of Irish potato and prevented storage root growth in sweetpotato. Excellent control of broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash], henbit (Lamium amplexicaule L.), prickly sida (Sida spinosa L.), and common ragweed (Ambrosia artemisiifolia L.) was obtained with metribuzin + metolachlor applied preemergence at Irish potato planting, followed by sethoxydim + crop oil applied postemergence in ST and CT systems. Redroot pigweed (Amaranthus retroflexus L.) control was >98% at 4 weeks after treatment but was 73% to 84% at harvest across all herbicide treatments in both tillage systems. In sweetpotato, control of black mustard [Brassica nigra (L.) W.J.D. Koch], goosegrass [Eleusine indica (L.) Gaertn.], and fall panicum [Panicum dichotomiflorum Michx.] was >95% throughout the growing season for all herbicide treatments in both ST and CT.

Weed Control with Bromoxynil Applied Alone and with Graminicides

Experiments were conducted in 1991 and 1992 to evaluate annual grass and broadleaf weed control with bromoxynil applied alone and with graminicides. Bromoxynil controlled velvetleaf better than entireleaf morningglory and controlled both species better than sicklepod. Mixing bromoxynil with fluazifop-P, quizalofop-P, and sethoxydim reduced control of barnyardgrass, green foxtail, large crabgrass, and shattercane. Control of broadleaf signalgrass with quizalofop-P was reduced by bromoxynil. Annual grass control with clethodim was not affected by bromoxynil.

Postemergence Grass Control in Sweet Potatoes (Ipomoea batatas)

Fluazifop-P, sethoxydim, and quizalofop were evaluated over two years for postemergence annual grass control in sweet potatoes. All treatments controlled broadleaf signalgrass and large crabgrass, but in 1987 only rates of at least 0.14 kg/ha of fluazifop-P and quizalofop and 0.28 kg/ha of sethoxydim controlled large crabgrass. No. 1 grade and total yield were greater from plots treated with herbicides compared with the weedy check in 1986. In 1987, No. 1 grade and total yield were greater in plots treated with fluazifop-P at 0.14 kg/ha or higher and sethoxydim or quizalofop at 0.28 kg/ha or higher.

Interactions of DPX-PE350 with Fluazifop-P, Sethoxydim, Clethodim, and Quizalofop-P

Interactions of fluazifop-P, sethoxydim, clethodim, and quizalofop-P with DPX-PE350 were evaluated. DPX-PE350 at 110 g ae ha−1reduced control of large crabgrass when mixed with all graminicides and control of broadleaf signalgrass when mixed with fluazifop-P or quizalofop-P. Increasing the rate of graminicide reduced or eliminated antagonism. Applying sethoxydim and DPX-PE350 sequentially eliminated antagonism on large crabgrass. Control of seedling johnsongrass by the graminicides was not reduced by DPX-PE350. DPX-PE350 reduced control of rhizomatous johnsongrass by sethoxydim. Graminicides had no effect on entireleaf morningglory control with DPX-PE350.

Clomazone as a Component in Cotton (Gossypium hirsutum) Herbicide Programs

Efficacy of herbicide programs containing clomazone PPI plus fluometuron PRE or clomazone plus pendimethalin PPI plus fluometuron PRE was compared with that of standard programs of pendimethalin PPI plus fluometuron PRE and norflurazon PPI plus norflurazon and fluometuron PRE. Cotton injury was less than 5% with all treatments when disulfoton or phorate was applied in the seed furrow. Control of fall panicum, goosegrass, large crabgrass, eclipta, entireleaf morningglory, ivyleaf morningglory, pitted morningglory, tall morningglory, prickly sida, redroot pigweed, smooth pigweed, hemp sesbania, spotted spurge, sicklepod, and velvetleaf and cotton yields with 0.8 kg ai ha−1 of clomazone plus fluometuron or 0.6 kg ha−1 of clomazone plus pendimethalin plus fluometuron equalled or exceeded that from the standard herbicide programs. POST-directed application of methazole at 0.8 kg ai ha−1 plus MSMA at 2.2 kg ae ha−1 increased sicklepod and morningglory control and cotton yield. Clomazone applied PRE at 0.6 kg ha−1 with fluometuron controlled broadleaf signalgrass, goosegrass, large crabgrass, prickly sida, and smooth pigweed equally with that of standard treatments of trifluralin or trifluralin plus norflurazon PPI and fluometuron PRE, whereas pitted morningglory control and cotton yield with clomazone plus fluometuron exceeded that with the standards.

Antagonism of Graminicide Activity on Annual Grass Species by Imazethapyr

The interaction of imazethapyr and selected graminicides on annual grass control was studied in field experiments. Tank-mix combinations of imazethapyr with clethodim, fluazifop-P, quizalofop, or sethoxydim resulted in an antagonistic interaction. Control of large crabgrass, fall panicum, and broadleaf signalgrass by each graminicide decreased when tank-mixed with imazethapyr as compared with each graminicide applied alone. Sequential applications of imazethapyr, relative to each graminicide, successfully overcame the antagonism. Imazethapyr applied 5 d before or 1 d after each of the graminicides did not decrease grass weed control compared with each graminicide alone. Imazethapyr applied 3 or 1 d before, or the same day as the graminicides, generally decreased grass weed control.

Annual Grass Control in Cotton (Gossypium hirsutum) with Fluazifop, Sethoxydim, and Selected Dinitroaniline Herbicides

One and two postemergence (POE) applications of the butyl ester of fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy]phenoxy] propanoic acid} or sethoxydim (2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} following preemergence (PRE) application of fluometuron {N,N-dimethyl-N′-[3-(trifluoromethyl)phenyl] urea} were compared to a preplant-incorporated (PPI) application of trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] or pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] plus fluometuron PRE or pendimethalin plus fluometuron PRE for annual grass control in cotton (Gossypium hirsutumL.) and net economic return to land, overhead, and management. One POE application of either fluazifop or sethoxydim following fluometuron PRE resulted in greater control of a high population of broadleaf signalgrass [Brachiaria platyphylla(Griseb.) Nash. # BRAPP] and greater yield and net return than a PPI application of trifluralin or pendimethalin plus fluometuron PRE. A second application of fluazifop or sethoxydim increased late-season control but did not increase yield or net return. In a high population of large crabgrass (Digitaria sanguinalisL. # DIGSA), fluometuron PRE plus two POE applications of fluazifop or sethoxydim resulted in grass control, lint yield, and net return similar to trifluralin or pendimethalin PPI plus fluometuron PRE. No differences in grass control, crop response, or net return were noted between PPI application of trifluralin or pendimethalin. Control of broadleaf signalgrass and large crabgrass with pendimethalin plus fluometuron PRE was less than with pendimethalin PPI plus fluometuron PRE. In fields with a low population of large crabgrass, fall panicum (Panicum dichotomiflorumMichx. # PANDI), and goosegrass [Eleusine indica(L.) Gaertn. # ELEIN], fluometuron PRE provided excellent season-long control. No benefits were obtained from addition of a grass herbicide. No treatments affected cotton maturity or fiber quality.

Integrating Sethoxydim into Soybean (Glycine max) Weed Management Systems

On-farm field experiments were conducted in the Piedmont Plateau and Coastal Plain of North Carolina in 1981 and 1982 to investigate the integration of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} with other chemical and cultural weed control tactics into soybean [Glycine max(L.) Merr.] weed management systems. Sethoxydim at 0.2 kg ai/ha provided control of broadleaf signalgrass [Brachiaria platyphylla(Griseb.) Nash. # BRAPP], large crabgrass [Digitaria sanguinalis(L.) Scop. # DIGSA], and fall panicum [Panicum dichotomiflorumMichx. # PANDI) equal to control achieved with registered rates of the soil-applied herbicides alachlor [2-chloro-2’,6’-diethyl-N-(methoxymethyl)acetanilide] and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). Control of broadleaf weed species with the postemergence herbicides bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4-(3H)-one 2,2-dioxide] and acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} equaled or exceeded the control obtained with the soil-applied herbicides linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5-(4H)-one]. Applications of 0.22 kg/ha of sethoxydim 2, 3, 4, and 5 weeks after soybean planting provided season-long control of fall panicum and crabgrass in 1981. In 1982, crabgrass control was 88 to 99% up to 4 weeks after planting. Later applications provided inadequate control of the grass species. Variations in volume and pressure of application had no effect on control of 10-cm goosegrass [Eleusine indica(L.) Gaertn. # ELEIN] or broadleaf signalgrass with 0.2 kg/ha of sethoxydim. Increasing pressure increased control of 30-cm goosegrass and broadleaf signalgrass. Increasing volume increased only control of goosegrass. Bentazon and acifluorfen provided better control of broadleaf weeds when applied early than when applied late. In two of four experiments tank mixtures of sethoxydim and bentazon resulted in an initial decrease in grass control compared to corresponding sequential applications. Soybean yields were comparable, however.

Management of Broadleaf Signalgrass (Brachiaria platyphylla) in Peanuts (Arachis hypogaea) with Herbicides

Field studies were conducted in 1978 and 1979 on broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] management in peanuts [Arachis hypogaea (L.) ‘Florigiant′]. In both years, preplant incorporated applications of benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] provided better than 75% initial control of broadleaf signalgrass. Preemergence applications of alachlor and metolachlor provided 90% or better initial control. Vernolate (S-propyl dipropylthiocarbamate) and diphenamid (N,N-dimethyl-2,2-diphenylacetamide) provided less than 45% initial control. An at-cracking application of dinoseb (2-sec-butyl-4,6-dinitrophenol) plus naptalam (N-1-naphthylphthalamic acid) plus either alachlor or metolachlor increased control over that provided by at-planting herbicides alone and maximum yields were obtained. No at-planting herbicide alone provided better than 60% control at harvest and consequently yields were lower. In three of four experiments, sequential applications of at-planting and at-cracking herbicides provided better than 75% control at harvest. In the fourth experiment, only benefin and metolachlor followed by at-cracking applications provided better than 70% control at harvest.

Molinate and Water Management for Weed Control in Rice

The herbicideS-ethyl hexahydro-1H-azepine-1-carbothioate [molinate] at 0, 3, and 6 lb/A was applied to drill-seeded rice [Oryza sativaL.] into the irrigation water at 8, 13, and 20 days after rice and weed emergence; the plots remained flooded for 2, 7, or 12 days. Three lb/A applied when weeds had 1 to 6 leaves and rice had 2 to 8 leaves controlled barnyardgrass [Echinochloa crusgalli(L.) Beauv.] and broadleaf signalgrass [Brachiaria platyphylla(Griseb.) Nash] and did not injure rice when the water remained for 7 or 12 days. Weed control and yield of rice were reduced when the irrigation water was held for only 2 days. When the weeds were tillering, molinate controlled barnyardgrass better than it controlled broadleaf signalgrass. Molinate at 0, 3, and 6 lb/A was applied to drill-seeded rice into the irrigation water 1 week after rice and weed emergence; 7 days later the water was either left on the plots or was drained for 5, 10, 20, or 29 days. Three lb/A usually prevented reinfestations of barnyardgrass when plots were drained for 5, 10, or 20 days. Barnyardgrass reinfested rice drained for 29 days and reduced yields.