The effects of sethoxydim {2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexene-1-one} rate, order, and timing of sequential herbicide applications, and the addition of oil concentrate on sethoxydimbentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H-one 2,2-dioxide] antagonism were studied on broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash. ♯3 BRAPP], fall panicum (Panicum dichotomiflorum Michx. ♯ PANDI), and large crabgrass [Digitaria sanguinalis (L.) Scop. ♯ DIGSA] in field experiments during 1980 and 1981. Tank-mixing bentazon with sethoxydim reduced control of these species compared to applications of sethoxydim alone. Sequential applications of the herbicides prevented the antagonism. Variations in time between and order of sequential applications had no consistent effect on efficacy. Increases in sethoxydim rate reduced the severity of the antagonism in some cases, while the addition of oil concentrate had no effect.

Greenhouse studies were conducted to determine host status of weed species for Rhizoctonia solani AG-1, which causes Rhizoctonia foliar blight of soybean. Weed species were barnyardgrass, broadleaf signalgrass, common cocklebur, entireleaf morningglory, hemp sesbania, itchgrass, johnsongrass, large crabgrass, northern jointvetch, prickly sida, purple nutsedge, redweed, sicklepod, and smooth pigweed. Seedling weeds were inoculated with suspensions containing intraspecific group IA and IB isolates of the fungus. In the first study, sclerotia of IA were recovered from tissue of all weeds except smooth pigweed, and mycelia of IA were recovered from all except smooth pigweed and redweed. In that study, neither microsclerotia nor mycelia of IB were recovered from sicklepod, barnyardgrass, or large crabgrass, and only microsclerotia were recovered from itchgrass and purple nutsedge. In the second study, sclerotia of IA, microsclerotia of IB, and mycelia of each isolate were recovered from all weed species. In other studies, R. solani spread from at least six of seven weed species to a noninfected soybean plant growing in close proximity. These studies emphasize the importance of weed control, not only for reducing plant competition and increasing yield, but also for the potential impact on development of RFB.

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.

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 hirsutum L.) 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 sanguinalis L. # 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 dichotomiflorum Michx. # 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.

A 3-yr study was initiated in 1982 to determine the effects of herbicides and crop rotations on large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] and broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash # BRAPP] population dynamics. Regardless of the crop rotation sequence, broadleaf signalgrass immediately became the predominant weed where standard herbicide programs were used. Large crabgrass became the predominant species after two growing seasons if no herbicides were applied. Domination by large crabgrass appeared to be due to greater seed production. The domination by broadleaf signalgrass in plots treated with herbicides was attributed to its tolerance to the primary grass herbicide alachlor [2-chloro-N-(2,6-diethylphenyl)-N-methoxymethyl)acetamide]. Broadleaf signalgrass emergence from soil treated with 2.2 kg ai/ha was not statistically different from that in untreated soil, while large crabgrass and fall panicum [Panicum dichotomiflorum (L.) Michx. # PANDI] emergence was significantly reduced at the same rate.

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.

Chlorimuron antagonized the activity of quizalofop on broadleaf signalgrass when applied in greenhouse studies as a postemergence tank mix. In vitro leaf disc assays utilizing 14C-acetate or 14C-pyruvate as substrates were conducted to ascertain the effect of clorimuron and quizalofop on fatty acid biosynthesis and to determine if antagonism between the two herbicides occurs at the biochemical sites of action. Incorporation of 14C-acetate in control treatments was linear with time to 120 min. Acetate incorporation in the presence of quizalofop (1.1 μM) was also linear but was inhibited 30 min after initialization of the reaction. The concentration of quizalofop that inhibited 14C-acetate incorporation 50% (I50) was 0.54 μM. Chlorimuron, up to 155 μM, had no effect on 14C-acetate incorporation. A mixture of quizalofop (1.1 μM) and chlorimuron (4.8 μM) inhibited 14C-acetate incorporation similar to that of quizalofop alone at 1.1 μM. Quizalofop I50 for incorporation of 14C-pyruvate was 1.1 μM, and clorimuron at 4.8 μM decreased incorporation 15%. Excess unlabeled pyruvate (5 μM) had no effect on either 14C-acetate or 14C-pyruvate incorporation in the presence of both herbicides. It is believed that antagonism of quizalofop by clorimuron is not due to an excess pool of pyruvate resulting from inhibition of acetolactate synthase by chlorimuron.

Field experiments evaluated barnyardgrass, broadleaf signalgrass, and rhizomatous johnsongrass control with sethoxydim, clethodim, fluazifop-P, quizalofop-P, and fenoxaprop applied alone and with bentazon or chlorimuron when crop oil concentrate or BCH 815 was used. Bentazon strongly antagonized sethoxydim and clethodim. BCH 815 partially reduced the antagonism with sethoxydim and clethodim compared with crop oil concentrate. Chlorimuron was most antagonistic towards fluazifop-P, fenoxaprop, and quizalofop-P, and BCH 815 did not reduce antagonism. Additional experiments evaluated Italian ryegrass control with diclofop applied alone and with bromoxynil, metribuzin, 2,4-D amine, or tribenuron plus thifensulfuron with these adjuvants. The amine formulation of 2,4-D and tribenuron plus thifensulfuron reduced Italian ryegrass control with diclofop, irrespective of the adjuvant.

Cloransulam-methyl applied postemergence (POST) following various preplant-incorporated (PPI) herbicides was evaluated in four experiments for weed control in North Carolina soybean over a 2-yr period at three locations. Acifluorfen plus bentazon or chlorimuron alone applied POST injured soybean more than cloransulam-methyl when following any soil-applied herbicide. When following trifluralin PPI, cloransulam-methyl controlled common ragweed, entireleaf morningglory, and pitted morningglory comparable to acifluorfen plus bentazon or chlorimuron. Common lambsquarters and prickly sida control was higher when acifluorfen plus bentazon was applied POST following trifluralin PPI compared to trifluralin PPI followed by cloransulam-methyl or chlorimuron. Acifluorfen plus bentazon or chlorimuron POST controlled yellow nutsedge and smooth pigweed more than cloransulam-methyl POST when following trifluralin PPI. When trifluralin was applied PPI in mixtures with chlorimuron plus metribuzin, flumetsulam, or imazaquin, control of most species was similar regardless of POST treatment used. Soybean treated with cloransulam-methyl yielded 250 kg/ha more than treatments with chlorimuron when these herbicides followed trifluralin plus flumetsulam or trifluralin plus imazaquin. Net returns with different herbicide systems followed trends similar to soybean yield.

Field experiments evaluated barnyardgrass, broadleaf signalgrass, and rhizomatous johnsongrass control with clethodim applied with Agri-Dex® crop oil concentrate at 1.0% v/v, the adjuvant Dash® at 1.0% v/v, the methylated seed oil Sun-It II® at 1.0% v/v, a blend of silicone surfactant plus methylated seed oil (Dyne-Amic® at 0.5% v/v) or nonionic surfactant (Kinetic® HV at 0.125% v/v), two silicone surfactants (Sylgard® 309 and Silwet L-77® surfactant) at 0.125% v/v, two other conventional nonionic surfactants (Latron AG-98™ and Induce®) at 0.25% v/v, and the acidified soya phospholipid LI-700®. When compared with the conventional nonionic or silicone-based surfactants and LI-700, clethodim at 70 g ai/ha controlled barnyardgrass more effectively when applied with Dash or Sun-It II. Broadleaf signalgrass and rhizomatous johnsongrass were controlled more effectively when clethodim was applied with Agri-Dex, Dash, Sun-It II, or Dyne-Amic. Clethodim at 70 g/ha applied with Dash or Sun-It II controlled grasses equally or greater than clethodim at 140 g/ha.

Thiazopyr at 0.14, 0.28, and 0.42 kg ai/ha and pendimethalin at 1.1 kg ai/ha applied preemergence (PRE) were compared as components in weed management systems for no-till cotton. Mid- and late-season control of mixtures of large crabgrass, goosegrass, and fall panicum by thiazopyr at 0.28 kg/ha was 89 to 97% and 11 to 50%, respectively, compared with 11 to 38% midseason and 0 to 5% late-season control by pendimethalin. Thiazopyr at 0.42 kg/ha and pendimethalin controlled broadleaf signalgrass 44 and 0%, respectively, late in the season. Adding fluometuron PRE at 1.7 kg ai/ha had little to no effect on large crabgrass, goosegrass, and fall panicum control but increased broadleaf signalgrass control 47 to 79 percentage points compared with thiazopyr or pendimethalin alone. Late-season control of annual grasses by thiazopyr or pendimethalin plus fluometuron PRE followed by methazole plus MSMA early postemergence (POST)-directed and cyanazine plus MSMA late POST-directed was at least 95% at two locations and 80% at the third location. Common lambsquarters was controlled 54 and 95% in systems without and with fluometuron PRE, respectively. Acceptable control of ivyleaf, pitted, and tall morningglories at all locations and smooth pigweed at two of three locations was achieved only in systems with POST-directed herbicides. Adding POST-directed herbicides to systems with thiazopyr or pendimethalin plus fluometuron PRE increased cotton yield at two of three locations. Treatments had no effect on fiber quality.

An experiment was conducted at four locations in North Carolina during 1994 and 1995 to evaluate weed control, cotton yield, fiber quality, and net returns in no-tillage bromoxynil-tolerant cotton. The experiment focused on using bromoxynil or pyrithiobac sodium applied early POST over-the-top as alternatives to fluometuron plus MSMA applied early POST directed. Fluometuron plus MSMA was more effective than bromoxynil or pyrithiobac sodium on tall morningglory, large crabgrass, goosegrass, and broadleaf signalgrass. Bromoxynil and fluometuron plus MSMA were similarly effective on common lambsquarters, common ragweed, and eclipta and more effective than pyrithiobac sodium. Pyrithiobac sodium and fluometuron plus MSMA were similarly effective on smooth pigweed and Palmer amaranth and more effective than bromoxynil. Prickly sida control by bromoxynil and pyrithiobac sodium was equal to or greater than control by fluometuron plus MSMA. All early POST herbicides controlled pitted morningglory similarly. Regardless of the early POST herbicides used, fluometuron applied PRE and cyanazine plus MSMA applied late POST directed increased control of most weeds and increased cotton yield and net returns. Bromoxynil and pyrithiobac sodium effectively substituted for fluometuron plus MSMA only in systems that included fluometuron applied PRE and cyanazine plus MSMA applied late POST directed. Effects of herbicide systems on cotton fiber quality were minor.

Greenhouse and field experiments were conducted to evaluate early postemergence (POST) tank mixtures of SAN 582 with fluazifop-P, imazethapyr, or sethoxydim. In the greenhouse, SAN 582 synergistically improved barnyardgrass, broadleaf signalgrass, and johnsongrass control from imazethapyr and sethoxydim. Half-rates of imazethapyr and sethoxydim tank-mixed with SAN 582 controlled grass weeds as well as full rates of either herbicide applied alone. Grass weed control with imazethapyr increased up to 40% with the addition of SAN 582. In field experiments, SAN 582 increased grass control with imazethapyr to a lesser degree than observed in the greenhouse. In a multispecies study, grass weed control increased up to 15% when SAN 582 was tank-mixed with a reduced rate of imazethapyr, although the full rate of imazethapyr applied POST with or without SAN 582 controlled grass weeds 80% or less. The combination of SAN 582 with sethoxydim was synergistic for barnyardgrass and johnsongrass control in this experiment. When applied POST in soybean, SAN 582 plus fluazifop-P or sethoxydim controlled barnyardgrass throughout the season better than a single POST application of a graminicide.

Clomazone was evaluated preplant incorporated (PPI) or post-transplant (PT) for weed control in sweet potatoes. No crop injury by clomazone was detected. Clomazone controlled (≥90%). broadleaf signalgrass, large crabgrass, barnyardgrass, and prickly sida at all rates and methods of application (MOA). Common cocklebur was controlled (≥93%) by clomazone at 1.1 kg ai ha-1 applied PT or at 3.4 kg ai ha-1 PPI in 1988 and at all rates and MOA in 1989. Clomazone did not control carpetweed.

Field experiments were conducted in 1984 and 1985 at Stuttgart, AR, to investigate the interspecific and intraspecific interference of broadleaf signalgrass densities of 0, 10, 50, 100, and 150 plants/m2 with rice. In 1984, significant reductions in rice leaf area index (LAI) occurred 6 weeks after emergence with all broadleaf signalgrass densities. The first reduction in LAI occurred 8 weeks after emergence at the density of 150 plants/m2 in 1985. Densities of 50 plants/m2 or greater reduced rice dry weight 6 weeks after emergence in 1984, and the highest density of 150 plants/m2 reduced rice dry weight 12 weeks after emergence in 1985. Height of rice was reduced by densities of 100 and 150 plants/m2. Linear regression equations indicated that each broadleaf signalgrass plant/m2 reduced rough rice yield 18 kg/ha both years. Growth of broadleaf signalgrass was reduced by interspecific and intraspecific interference. The dry weight of broadleaf signalgrass increased at a decreasing rate at plant densities of 100 to 150/m2 when grown alone in 1984 and 1985, when a quadratic equation best described the response. Regression equations indicated interspecific interference from rice reduced broadleaf signalgrass dry weight an average of 48 and 81% in 1984 and 1985, respectively. The height of broadleaf signalgrass was greater when grown with rice than when grown alone.

CGA 82725 {2-propynyl [2-[4-[(3,5-dichloro-2-pyridinyl)oxy)] phenoxy] propanoate}, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy]phenoxy] propanoic acid}, sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, and fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} were applied postemergence to Texas panicum (Panicum texanum Buckl. # PANTE), large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA], and broadleaf signalgrass [Brachiaria platyphylla (Griseb.)Nash. # BRAPP] in peanut (Arachis hypogaea L. ‘Florunner’). Fluazifop applied at 280 and 410 g ai/ha, sethoxydim at 340 g ai/ha, haloxyfop at 140 g ai/ha, and CGA 82725 at 280 g ai/ha usually gave better control when applied to annual grasses in the two- to four-leaf stage than when applied at the six- to eight-leaf stage. Higher rates of application were required to provide acceptable weed control at the later stage of growth. Peanut yields were usually higher following the early applications, indicating that timing of application is important in obtaining improved yields.

Studies were conducted to measure the foliar activity of sethoxydim (BAS 9052 OH) {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl-3-hydroxy-2-cyclohexen-1-one} and RO-13-8895 {acetone-O-[D-2-[p-[(α,α,α-trifluoro-p-tolyl)-oxy] phenoxy] propionyl] oxime} as affected by adjuvants, soil moisture, and growth stage of grasses, and to compare the responses of three grass species to these herbicides. The activity of both herbicides was increased by adjuvants. The activity of sethoxydim was not significantly affected by soil moisture. Goosegrass [Eleusine indica (L.) Gaertn. ♯3 ELEIN] and broadleaf signalgrass [Brachiaria platyphylla (Griseb. ♯ BRAPP) Nash] control was greater with RO-13-8895 at the high than at the low soil moisture level. Soil moisture did not influence large crabgrass [Digitaria sanguinalis (L.) Scop. ♯ DIGSA] control, since it was relatively tolerant to RO-13-8895. Both herbicides gave greater control at early than at late growth stages. When averaged over all variables, sethoxydim gave greater large crabgrass control than RO-13-8895, but RO-13-8895 gave greater goosegrass and broadleaf signalgrass control than sethoxydim.

An experiment was conducted at five locations in North Carolina to compare management systems utilizing glufosinate applied postemergence (POST) in glufosinate-resistant corn with standard systems of metolachlor plus atrazine preemergence (PRE) or nicosulfuron plus atrazine POST Glufosinate alone and both standard systems controlled common ragweed and prickly sida at least 98%, whereas sicklepod control was < 20% late in the season. Late-season control of common lambsquarters, smooth pigweed, pitted morningglory, and tall morningglory was generally less with glufosinate alone than with the standard systems. However, late-season control of common lambsquarters, smooth pigweed, pitted morningglory, tall morningglory, and sicklepod by mixtures of glufosinate plus atrazine was at least 99, 100, 89, 93, and 81%, respectively, and was equal to or greater than control by either standard. Broadleaf signalgrass, large crabgrass, and fall panicum were controlled similarly by glufosinate and the standards. Goosegrass control by glufosinate was similar to control by nicosulfuron plus atrazine, but it was less than control by metolachlor plus atrazine. Metolachlor applied PRE or atrazine mixed with glufosinate increased goosegrass control to that achieved with metolachlor plus atrazine. Mixing atrazine with glufosinate did not affect fall panicum control, but metolachlor PRE followed by glufosinate controlled fall panicum as well as the standards. Cultivation or ametryn applied at layby increased control when PRE or POST herbicides alone controlled weeds less than about 90%. Ametryn was generally more effective than cultivation. Glufosinate POST followed by ametryn at layby controlled sicklepod > 90% and other species > 95% late in the season. Corn yield and net returns were similar in the glufosinate and standard systems.

Field experiments were conducted in 1982 and 1983 in cotton (Gossypium hirsutum L.) to evaluate alternatives in grass weed management programs with the use of postemergence herbicides and to assess the economic potential for incorporating the new over-the-top grass weed herbicides into total cotton production practices. Twelve weed management systems using the grass herbicides sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} and fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid} were compared to six standard systems. Differences in cotton production costs among the 18 systems were due to cost differences in total weed management. Equal or greater net return values were obtained when over-the-top herbicides followed fluometuron {N,N-dimethyl-N′-[3-(trifluoromethyl)phenyl)urea} preemergence or when these materials were applied twice compared to the over-the-top materials used in conjunction with trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] preplant incorporated or with directed postemergence materials. High net returns were the result of both high seed cotton yields and low total production costs.

The isopropylamine salt of glyphosate at 420, 560, and 840 g ae/ha applied alone or mixed with the sodium salt of bentazon at 840 g ai/ha, chlorimuron at 9 g ai/ha, the sodium salt of fomesafen at 350 g ai/ha, or the ammonium salt of imazethapyr at 70 g ae/ha was evaluated for control of large crabgrass and broadleaf signalgrass. Neither grass was controlled by bentazon, fomesafen, or chlorimuron. Imazethapyr controlled large crabgrass and broadleaf signalgrass 30 and 72%, respectively, 3 weeks after treatment (WAT). Glyphosate at all rates controlled both grasses 100%. Control 3 WAT was unaffected by mixing bentazon, chlorimuron, fomesafen, or imazethapyr with glyphosate. Broadleaf signalgrass control 1 WAT was reduced 4 to 15% by mixing bentazon with glyphosate.