Conservation tillage adoption continues to be threatened by glyphosate and acetolactate synthase–resistant Palmer amaranth and other troublesome weeds. Field experiments were conducted from autumn 2010 through crop harvest in 2013 at two locations in Alabama to evaluate the effect of integrated management practices on weed control and seed cotton yield in glyphosate-resistant cotton. The effects of a cereal rye cover crop using high- or low-biomass residue, followed by wide or narrow within-row strip tillage and three PRE herbicide regimens were evaluated. The three PRE regimens were (1) pendimethalin at 0.84 kg ae ha−1 plus fomesafen at 0.28 kg ai ha−1 applied broadcast, (2) pendimethalin plus fomesafen applied banded on the row, or (3) no PRE. Each PRE treatment was followed by (fb) glyphosate (1.12 kg ae ha−1) applied POST fb layby applications of diuron (1.12 kg ai ha−1) plus monosodium methanearsonate (2.24 kg ai ha−1). Low-residue plots ranged in biomass from 85 to 464 kg ha−1, and high-biomass residue plots ranged from 3,119 to 6,929 kg ha−1. In most comparisons, surface disturbance width, residue amount, and soil-applied herbicide placement did not influence within-row weed control; however, broadcast PRE resulted in increased carpetweed, large crabgrass, Palmer amaranth, tall morning-glory, and yellow nutsedge weed control in row middles compared with plots receiving banded PRE. In addition, high-residue plots had increased carpetweed, common purslane, large crabgrass, Palmer amaranth, sicklepod, and tall morning-glory weed control between rows. Use of banded PRE herbicides resulted in equivalent yield and revenue in four of six comparisons compared with those with broadcast PRE herbicide application; however, this would likely result in many between-row weed escapes. Thus, conservation tillage cotton would benefit from broadcast soil-applied herbicide applications regardless of residue amount and tillage width when infested with Palmer amaranth and other troublesome weed species.

During 2016 and 2017, four field experiments were conducted at Huron Research Station near Exeter, ON, to evaluate the sensitivity of dry bean grown under a strip-tillage cropping system, to potential herbicides for the control of glyphosate-resistant (GR) horseweed. At 8 wk after emergence (WAE), saflufenacil, metribuzin, saflufenacil+metribuzin, 2,4-D ester, flumetsulam, cloransulam-methyl, and chlorimuron-ethyl caused 13% to 32%, 8% to 52%, 32% to 53%, 5% to 7%, 13% to 21%, 16% to 29%, and 23% to 43% visible injury in dry beans, respectively. Saflufenacil decreased aboveground biomass 65% in kidney bean and 80% in white bean. Metribuzin decreased biomass 82% in kidney bean and 50% in white bean. Saflufenacil+metribuzin decreased biomass 88% in kidney bean, 68% in small red bean, and 80% in white bean. Chlorimuron-ethyl decreased biomass 40% in white bean. There was no decrease in dry bean biomass with the other herbicides evaluated. Metribuzin and saflufenacil+metribuzin reduced kidney bean seed yield 72% and 76%, respectively. Saflufenacil+metribuzin, flumetsulam, cloransulam-methyl, and chlorimuron-ethyl reduced small red bean seed yield 39%, 27%, 30%, and 54%, respectively. Saflufenacil, metribuzin, saflufenacil+metribuzin, flumetsulam, cloransulam-methyl, and chlorimuron-ethyl reduced seed yield of white bean 52%, 32%, 62%, 33%, 42%, and 62%, respectively. There was no decrease in dry bean yield with the other herbicides evaluated. Among herbicides evaluated, 2,4-D ester caused the least crop injury with no effect in dry bean seed yield.

Navua sedge is a creeping perennial sedge commonly found in tropical environments and is currently threatening many agroecosystems and ecosystems in Pacific Island countries and northern Queensland, Australia. Pasture and crop productions have been significantly impacted by this weed. The efficacy of halosulfuron-methyl on Navua sedge plants with and without well-established rhizomes was evaluated under glasshouse conditions. Halosulfuron-methyl was applied to plants with established rhizomes at three stages; mowed, pre-flowering, and flowering growth stages, whereas plants without established rhizomes were treated at seedling, pre-flowering and flowering growth stages. At each application time, halosulfuron-methyl was applied at four dose rates of 0, 38, 75, and 150 g ai ha−1. Mortality of 27.5%, 0%, and 5% was recorded in rhizomatous Navua sedge when treated with 75 g ai ha−1 of halosulfuron-methyl at the mowed, pre-flowering stage and flowering stages, respectively. At 10 wk after treatment (WAT), there were no tillers in surviving plants treated at any of the application times. By 16 WAT, the number of tillers increased to 15, 24, and 26 in mowed, pre-flowering, and flowering stages, respectively. Although halosulfuron-methyl is effective in controlling aboveground growth, subsequent emergence of new growth from the rhizome confirms the failure of the herbicide to kill the rhizome. Application of 75 g ai ha−1 of halosulfuron-methyl provided 100% mortality in plants treated at seedling and pre-flowering stages, and 98% mortality when treated at flowering stage in non-rhizomatous plants. A single application of halosulfuron-methyl is highly effective at controlling Navua sedge seedlings but not effective at controlling plants with established rhizomes.

Cholla infestations can be problematic on rangelands in North America, Australia, Africa, and Europe, and treatment options for this plant are limited because of its ability to resprout from broken stem fragments. We investigated dragged-rail treatments, where iron rails are dragged across the rangeland by tractor and knock plants over while uprooting them, as a treatment option for tree cholla in southeast New Mexico. Railing effectively controlled tree cholla plants over 0.5 m tall, but did not effectively control plants smaller than 0.5 m. Nevertheless, treatment did effectively reduce overall cholla density: Treated areas averaged 40 to 50 plants ha−1, whereas nontreated areas averaged over 350 plants ha−1. Railing can be an effective means of cholla control, especially if followed by another treatment, such as prescribed fire, that is known to be effective against the smaller sizes of cholla.

The continued phase-out of methyl bromide (MBr) challenges vegetable growers' abilities to control weeds in plasticulture production. Herbicides, such as EPTC (S-ethyl dipropylthiocarbamate), may be needed as part of a MBr alternative system. An experiment was conducted during the springs of 2008 and 2009 in Ty Ty, GA, to determine tomato, pepper, eggplant, and watermelon tolerance to EPTC applied under mulch. Treatments consisted of a factorial arrangement of four rates of EPTC (0, 2, 3, or 4 kg ai ha−1) and two plastic mulch types (low density polyethylene [LDPE] mulch or a high barrier mulch [HBM]). Each crop was planted 28 d after applying herbicides and laying mulch. EPTC, regardless of rate, applied under LDPE mulch did not impact plant growth, fruit number produced, or fruit weights for any crop. Conversely, pepper, tomato, and eggplant heights were reduced 65 to 72%, 30 to 75%, and 9 to 32%, respectively, by EPTC at 2 to 4 kg ai ha−1 when applied under HBM. Similar trends were observed for crop yield; fruit number and weight were reduced by 71 to 84% for pepper, 36 to 76% for tomato, and 7 to 15% for eggplant when EPTC was applied at 2 to 4 kg ai ha−1 as compared to the no EPTC HBM control. Watermelon stem lengths, fruit number, and fruit weights were not impacted by EPTC applied under HBM mulch. It appears as though HBMs reduce the loss of EPTC through volatilization, thereby increasing the dose present at time of planting. EPTC could be included as part of a MBr alternative system for tomato, pepper, eggplant, and watermelon when applied under LDPE mulch, and may also be applied at labeled rates with the HBM utilized in this experiment for watermelon.

Macartney rose is an aggressive, thorny shrub that suppresses forage production and strongly hinders cattle grazing in southern pastures. Previous studies have found this weed to be extremely difficult to control with most pasture herbicides. We conducted two studies in central Alabama to assess several new herbicide chemistries applied at spring, early fall, and late fall timings. In the first study, we compared aminocyclopyrachlor, tank mixed with either 2,4-D, triclopyr, metsulfuron, or chlorsulfuron, with the commercial standard, picloram + 2,4-D. In the second study, we compared aminopyralid, tank mixed with either 2,4-D or metsulfuron and triclopyr + fluroxypyr, to the commercial standard, picloram + 2,4-D. Aminocyclopyrachlor + chlorsulfuron or metsulfuron and aminopyralid + 2,4-D or metsulfuron provided acceptable control and were comparable to picloram + 2,4-D at the early fall timing. Macartney rose control with treatments applied at the late fall timing tended to be less than commercially acceptable levels. We found that no herbicide treatment controlled Macartney rose at the spring timing. In addition, triclopyr + fluroxypyr did not control Macartney rose at any application timing. These results indicate that the early fall timing was optimal and that both aminocyclopyrachlor and aminopyralid can provide good Macartney rose control when mixed with certain other herbicides, including metsulfuron.

In the southeastern United States, growers often double-crop soft red winter wheat with peanut. In some areas, tobacco is also grown as a rotational crop. Pyrasulfotole is a residual POST-applied herbicide used in winter wheat, but information about its effects on rotational crops is limited. Winter wheat planted in autumn 2014 was treated at Feekes stage 1 or 2 with pyrasulfotole at 300 or 600 g ai ha−1. Wheat was terminated by glyphosate at Feekes stage 3 to 4. Peanut was planted via strip tillage, while tobacco was transplanted into prepared beds after minimal soil disturbance. Peanut exhibited no differences in stand establishment, growth, or yield, and tobacco stand, growth, and biomass yields were not different from the nontreated control for any pyrasulfotole rate or treatment timing.

If registered for use on vegetable soybean, pyroxasulfone would expand the options for weed management systems in the crop. In order to determine the potential crop injury risk of pyroxasulfone on vegetable soybean, the objective of this work was to quantify vegetable soybean tolerance to pyroxasulfone applied PRE and EPOST. Twenty-one vegetable soybean and two grain-type soybean cultivars were treated with pyroxasulfone at 417 gaiha−1 (twice the recommended field use rate) PRE, EPOST, or not treated. Plant population density was unaffected by pyroxasulfone. Only low levels (<10%) of crop injury were observed within a few weeks after PRE and EPOST treatments. Soybean cultivars were not differentially affected by pyroxasulfone, as evidenced by the lack of interactions between cultivar and treatment for any crop response variable. The low amount of risk of crop injury associated with pyroxasulfone is no different for vegetable soybean cultivars grown in the US for commercial production than grain-type soybean.

A study was conducted at three locations in Louisiana to evaluate the interactions of imazamox at 44 g ai ha−1 mixed with propanil, thiobencarb, or with a prepackaged mixture of propanil plus thiobencarb. A synergistic response was observed for red rice control for all treatments at 14 days after treatments (DAT); however, at 21 DAT a neutral response was observed for imazamox mixed with propanil or thiobencarb. A synergistic response occurred for red rice control when imazamox was mixed with propanil plus thiobencarb at 3360 g ai ha−1 for all evaluation dates; however, imazamox mixed with propanil plus thiobencarb at 1680 g ha−1 resulted in synergism at the same evaluations except at 35 DAT with neutral response. Synergism was observed for barnyardgrass control with imazamox mixed with propanil plus thiobencarb at 3360 g ha−1 at 35 and 49 DAT. The only antagonism observed for barnyardgrass control was at 42 DAT with imazamox plus propanil at 840 and 1680 g ha−1 or mixed with the prepackage mixture at 1680 g ha−1. Rice treated with imazamox mixed with propanil plus thiobencarb at 3360 g ha−1 yielded 5770 kg ha−1.

Only four herbicides are registered for smooth crabgrass or goosegrass control on creeping bentgrass golf putting greens. None of the four herbicides control weedy grasses for the entire season or control weeds postemergence when applied once at labeled rates. Three of the product labels prohibit repeated use or application during stressful summer conditions. We hypothesized frequently applying herbicides at low doses could provide season-long control of summer grasses while minimizing turf injury. Seven field experiments were conducted on creeping bentgrass putting greens to evaluate various herbicides applied monthly, biweekly, or weekly for postemergence and residual control of goosegrass and smooth crabgrass as well as creeping bentgrass putting green tolerance. Metamifop applied twice monthly at 200 g ai ha−1, topramezone applied eight times weekly at 1.5 g ae ha−1, and siduron applied weekly at 5.6 kg ai ha−1 or four times biweekly at 11 kg ha−1 did not injure creeping bentgrass greater than 10% and maintained creeping bentgrass quality and cover equivalent to nontreated turf. Weekly or biweekly programs of fenoxaprop or quinclorac caused unacceptable injury and quality decline. Metamifop applied monthly and either fenoxaprop program controlled both smooth crabgrass and goosegrass by 97% to 99% throughout the growing season. Programs containing either quinclorac or siduron controlled smooth crabgrass by 99% to 100% but did not control goosegrass greater than 39%. All topramezone programs controlled smooth crabgrass by 69% to 77% and goosegrass by 93% to 98%. In additional studies, siduron applied five times biweekly did not injure creeping bentgrass on putting greens and controlled smooth crabgrass by more than 90% at seasonal, cumulative rates between 17 and 65 kg ai ha−1. This method of frequent, low-dose herbicide treatment to control smooth crabgrass and goosegrass on golf putting greens is novel and currently could be legally implemented with siduron.

A 2-yr study was conducted to evaluate bell pepper response and honeyvine milkweed control from PRE herbicides, clomazone and trifluralin, applied under polyethylene mulch. Clomazone (0.8 and 1.4 kg ai ha−1) and trifluralin (0.7 and 1.1 kg ai ha−1) were applied alone or in combination. Herbicides were applied after beds were made and before polyethylene mulch was laid, followed by transplanting pepper within hours of herbicide application. In both years, initial bleaching of lower leaves was observed; the injury was observed in some treatments, but not others. Honeyvine milkweed, growing in the planting hole, exhibited significant bleaching and stunting in most herbicide treatments. Both clomazone and trifluralin resulted in season-long honeyvine milkweed control in both years. However, the use of clomazone and trifluralin together for control of honeyvine milkweed does not seem justified due to the potential for herbicide antagonism, as indicated in this study. The total number and fresh weight of harvested bell pepper were not affected by the herbicides or rates. All herbicide treatments resulted in about twice the yield (average of 8.8 kg) of the hand-weeded control (4.6 kg) in both years. This study strongly supports the safety and effectiveness of clomazone and/or trifluralin applied pretransplant under polyethylene mulch in bell pepper production for control of honeyvine milkweed.

Experiments were conducted to evaluate the impact of spray volume, nozzle type, adjuvants, the presence of dew, and their interactions on foliar retention of creeping bentgrass. Tartrazine, a common food dye, was used as a tracer in this study. Increasing spray volume from 95 L ha−1 to 1,500 L ha−1 decreased foliar retention efficiency from 98% to approximately 85%. Compared with flat-fan nozzles, air-induction nozzles delivered similar retention efficiency at all spray volumes evaluated. However, flat-fan nozzles provided higher uniformity and more thorough coverage. Adding nonionic surfactants, organosilicone adjuvants, or methylated seed oils at typical concentrations yielded retention efficiency of approximately 90% to 93% regardless of spray volumes. In contrast, with water alone, increasing spray volume reduced retention efficiency from 95.9% to 87.3%. Simulated dew applied at 1,950 L ha−1 increased retention efficiency by approximately 3% when spray application volume was 190 L ha−1, while no difference was observed at 750 L ha−1. The presence of dew reduced the impact of adjuvants on retention efficiency. Large quantities of dew, 3,800 L ha−1, did reduce retention efficiency.

The objective for this study was to determine if POST-directed applications of flumioxazin reduce fruit yield for chile pepper produced on coarse- and fine-textured soils irrigated by furrow. This objective was addressed with a multiyear (2015, 2016, 2017) field study that compared flumioxazin effects on fruit yield against a commercial standard (POST-directed carfentrazone) and the absence of a POST-directed herbicide. The field study occurred at two university research farms that differed in soil texture. On fine-textured soil, treatments included the no POST–directed herbicide control and the following four POST-directed herbicides applied to raised beds: (1) flumioxazin at 107 g ai ha–1 applied 4 wk after crop thinning, (2) carfentrazone at 35 g ai ha–1 applied 4 wk after crop thinning, (3) flumioxazin at 70 g ai ha–1 applied 4 and 6 wk after crop thinning, (4) carfentrazone at 35 g ai ha–1 applied 4 and 6 wk after crop thinning. On coarse-textured soil, treatments included the no POST–directed herbicide control and the following three POST-directed herbicides applied 4 wk after crop thinning: (1) flumioxazin at 107 g ai ha–1 applied to raised beds, (2) flumioxazin at 107 g ai ha–1 applied to furrows, (3) carfentrazone at 35 g ai ha–1 applied to raised beds. On fine-textured soil, treatment did not affect fruit yield. On coarse-textured soil, flumioxazin applied to furrows did not reduce fruit yield, but flumioxazin on raised beds reduced fruit yield of some cultivars in 2015 and 2017. Year-to-year variability in both flumioxazin-induced yield loss and soil characteristics suggested that chile pepper sensitivity to flumioxazin was negatively associated with soil organic matter content. In a follow-up greenhouse study, soil organic matter lessened flumioxazin-induced crop injury. In general, this study indicates that recommendations for POST-directed flumioxazin in New Mexico chile pepper will need to be soil-type specific.

Pigweed is difficult to manage in grain sorghum because of widespread herbicide resistance, a limited number of registered effective herbicides, and the synchronous emergence of pigweed with grain sorghum in Kansas. The combination of cultural and mechanical control tactics with an herbicide program are commonly recognized as best management strategies; however, limited information is available to adapt these strategies to dryland systems. Our objective for this research was to assess the influence of four components, including a winter wheat cover crop (CC), row-crop cultivation, three row widths, with and without a herbicide program, on pigweed control in a dryland system. Field trials were implemented during 2017 and 2018 at three locations for a total of 6 site-years. The herbicide program component resulted in excellent control (>97%) in all treatments at 3 and 8 weeks after planting (WAP). CC provided approximately 50% reductions in pigweed density and biomass for both timings in half of the site-years; however, mixed results were observed in the remaining site-years, ranging from no attributable difference to a 170% increase in weed density at 8 WAP in 1 site-year. Treatments including row-crop cultivation reduced pigweed biomass and density in most site-years 3 and 8 WAP. An herbicide program is required to achieve pigweed control and should be integrated with row-crop cultivation or narrow row widths to reduce the risk of herbicide resistance. Additional research is required to optimize the use of CC as an integrated pigweed management strategy in dryland grain sorghum.

Information on performance of sequential treatments of quizalofop-P-ethyl with florpyrauxifen-benzyl on rice is lacking. Field studies were conducted in 2017 and 2018 in Stoneville, MS, to evaluate sequential timings of quizalofop-P-ethyl with florpyrauxifen-benzyl included in preflood treatments of rice. Quizalofop-P-ethyl treatments were no quizalofop-P-ethyl; sequential applications of quizalofop-P-ethyl at 120 g ha−1 followed by (fb) 120 g ai ha−1 applied to rice in the 2- to 3-leaf (EPOST) fb the 4-leaf to 1-tiller (LPOST) growth stages or LPOST fb 10 d after flooding (PTFLD); quizalofop-P-ethyl at 100 g ha−1 fb 139 g ha−1 EPOST fb LPOST or LPOST fb PTFLD; quizalofop-P-ethyl at 139 g ha−1 fb 100 g ha−1 EPOST fb LPOST and LPOST fb PTFLD; and quizalofop-P-ethyl at 85 g ha−1 fb 77 g ha−1 fb 77 g ha−1 EPOST fb LPOST fb PTFLD. Quizalofop-P-ethyl was applied alone and in mixture with florpyrauxifen-benzyl at 29 g ai ha−1 LPOST. Visible rice injury 14 d after PTFLD (DA-PTFLD) was no more than 3%. Visible control of volunteer rice (‘CL151’ and ‘Rex’) 7 DA-PTFLD was similar and at least 95% for each quizalofop-P-ethyl treatment. Barnyardgrass control with quizalofop-P-ethyl at 120 fb 120 g ha−1 LPOST fb PTFLD was greater (88%) in mixture with florpyrauxifen-benzyl. The addition of florpyrauxifen-benzyl to quizalofop-P-ethyl increased rough rice yield when quizalofop-P-ethyl was applied at 100 g ha−1 fb 139 g ha−1 EPOST fb LPOST. Sequential applications of quizalofop-P-ethyl at 120 g ha−1 fb 120 g ha−1 EPOST fb LPOST, 100 g ha−1 fb 139 g ha−1 EPOST fb LPOST, or 139 g ha−1 fb 100 g ha−1 EPOST fb LPOST controlled grass weed species. The addition of florpyrauxifen-benzyl was not beneficial for grass weed control. However, because quizalofop-P-ethyl does not control broadleaf weeds, florpyrauxifen-benzyl could provide broad-spectrum weed control in acetyl coenzyme A carboxylase–resistant rice.

Field studies were conducted in 2014 and 2015 at Pontotoc, MS to evaluate combinations of metam-potassium and S-metolachlor for yellow nutsedge control and sweetpotato crop response. Treatments consisted of a factorial of five metam-potassium rates (0, 149, 261, 372, and 484 kgha−1) by three S-metolachlor rates (0, 0.80, and 1.34 kgha−1). Additionally, a hand-weeded check was included for comparison. Crop injury was limited to ≤4% at 4 weeks after transplanting (WAP) and was transient. At 2 WAP yellow nutsedge control was 58, 74, and 76% in plots treated with S-metolachlor at 0, 0.80, and 1.34 kgha−1, respectively. Nutsedge control in all treatments decreased from 2 to 15 WAP. At 15 WAP, S-metolachlor at 0, 0.80, and 1.34 kg ha−1 provided 35, 68, and 70% yellow nutsedge control, respectively. Metam-potassium rate did not influence yellow nutsedge control after transplanting. Sweetpotato yields in the hand-weeded check were 4,640; 22,180; 7,180; 34,000; and 1,360 kgha−1 for jumbo, no. 1, canner, marketable, and cull grades, respectively. S-metolachlor applied at either 0.80 or 1.34 kgha−1 provided jumbo, no. 1, and marketable sweetpotato yields equivalent to the hand-weeded check. Canner and cull yields were not influenced by S-metolachlor rate. Metam-potassium rates used in the present study resulted in yields equal to or greater than the hand-weeded check.

Inadequate corn stands due to extreme weather conditions may require producers to replant their corn fields. The use of GR corn, however, can result in difficulty in managing replanted corn without experiencing yield loss. Therefore, the objectives of this research were to evaluate the herbicide options for control of GR corn in a corn replant situation and to determine the effect of corn replanted into various initial corn stands on grain yield. Two field studies were conducted to accomplish the objectives. The first experiment was designed to identify the most efficacious herbicide treatment for GR corn removal in a corn replant situation. Clethodim (51 g ai ha−1) applied 6 d prior to replanting, paraquat (700 g ai ha−1) plus metribuzin (160 g ai ha−1) applied at replanting, and glufosinate (450 g ai ha−1) applied at replanting along with a sequential treatment 3 wk later provided 96 to 100% control of the initial corn stand and resulted in the highest yield. If corn from the first planting remains, the interaction between different sized plants can reduce yield of corn. Thus, a second field experiment was conducted to evaluate the influence on grain yield of corn replanted into various initial corn stands. Corn stands of 0, 20,000, 40,000, 60,000, 80,000, and 100,000 plants ha−1 were established and either followed by a corn replant at 80,000 seeds ha−1 or not replanted. Initial stands ≥ 60,000 plants ha−1 did not require a replant to maximize yield. Initial corn stands ≤ 40,000 plants ha−1 required a replant with initial stand control to maximize grain yield. The percent yield contribution from an initial stand of 20,000 plants ha−1 was 20% greater than the same population replanted a few weeks later, which showed the competitive advantage to earlier planting even at the lowest initial corn stand. Because of this competitive advantage, an initial stand must be removed to maximize corn yield in a replant situation.

Praxelis is an annual to short-lived perennial herb in the Asteraceae family and an emerging problematic weed species in Florida nurseries. The objective of these experiments was to determine efficacy of selected PRE and POST herbicides for control of praxelis. An additional experiment was conducted to determine efficacy of the same PRE herbicides for control of bluemink, a weed similar in appearance to praxelis that is also common in Florida. The granular herbicides dimethenamid + pendimethalin, flumioxazin, oxyfluorfen + pendimethalin, oxyfluorfen + prodiamine, and trifluralin + isoxaben were evaluated, along with spray-applied formulations of dimethenamid, indaziflam, and prodiamine + isoxaben. Flumioxazin consistently provided over 90% control of praxelis at both sites. Indaziflam control was inconsistent between the two sites, providing 100% control in Apopka but only a 22% reduction in weed counts in Balm. Oxyfluorfen + pendimethalin, oxyfluorfen + prodiamine, and prodiamine + isoxaben also provided control (57% to 97% reduction in shoot weight), albeit generally to a lesser degree than was observed with flumioxazin. All PRE herbicides provided similar control of both praxelis and bluemink, with the exception of dimethenamid and dimethenamid + pendimethalin, which reduced bluemink shoot weight more than praxelis. Clopyralid, glyphosate, and triclopyr all provided effective POST control of mature and flowering praxelis through 12 wk after treatment (WAT) and resulted in greater praxelis control than glufosinate. Results suggest that many commonly used PRE and POST herbicides would provide control of praxelis, but use of PRE and POST herbicides as well as sequential applications may be needed for long-term management.

Allowing the use of two additional modes of action (MOAs), Enlist™ corn is a novelty in the continuum of herbicide-resistant crop development efforts that have occurred since the 1990s. Knowledge of Enlist corn tolerance to labeled herbicides and other herbicides within the same MOA for various use and/or exposure scenarios is not well established. Four site-year field experiments for preemergence (PRE) and postemergence (POST) applications were conducted at sites in Fayetteville (2021 and 2022) and Tillar (2020 and 2021), Arkansas, to evaluate Enlist corn response following PRE or POST applications of synthetic auxin herbicides or those that inhibit acetyl-CoA carboxylase (ACCase). A non-Enlist and an Enlist corn hybrid were used for each herbicide treatment to establish differential tolerance. Injury response to PRE application varied among site-years; clethodim was the only herbicide that occasionally caused significant (7% to 17%) injury to Enlist corn. None of the PRE treatments affected plant height, stand, or yield of Enlist corn; these responses were generally similar or better for Enlist corn compared to non-Enlist corn. Enlist corn showed significant injury to POST applications of florpyrauxifen-benzyl (>10%), fluazifop-P-butyl and quizalofop-P-ethyl (>5%), and clethodim and sethoxydim (>75%) 1 wk after application (WAA). These initial injury responses to clethodim and sethoxydim were generally reflected in Enlist corn yield; however, the minimal injury from fluazifop-P-butyl and quizalofop-P-ethyl did not affect yield. Injury to non-Enlist corn with POST-applied ACCase-inhibiting herbicides 2 WAA was >80%, resulting in a proportionate yield reduction. Even though florpyrauxifen-benzyl caused more initial injury to non-Enlist corn, yield reduction in non-Enlist corn was occasionally less than of Enlist corn, with both hybrids experiencing >75% yield reduction. In summary, Enlist corn may occasionally show transient injury even to labeled herbicides when applied POST, and even though the injury from florpyrauxifen-benzyl is initially mild, it nonetheless results in substantial yield loss.

A paper-based survey was conducted from 2015 to 2017 among stakeholders of the Texas rice industry on current weed management challenges and factors influencing management decisions. A total of 108 survey questionnaires were completed by stakeholders at the rice Cooperative Extension meetings conducted in the rice-growing counties of Texas. In addition, late-season field surveys were conducted prior to harvest in 2015 and 2016 across the rice-growing counties to understand dominant weed escapes occurring in rice fields. Results from the questionnaire survey revealed that rice–fallow–rice was the most common rotation practiced in Texas rice production. Echinochloa spp., Leptochloa spp., and Cyperus spp. were the top three problematic weed issues faced by the respondents. Among the Leptochloa species, Nealley’s sprangletop, a relatively new species in rice fields, was indicated as an emerging concern. Clomazone was the most frequently used PRE herbicide, whereas quinclorac, propanil, imazethapyr, and cyhalofop were the popular POST herbicides. Most respondents (72%) made weed-control decisions on the basis of economic thresholds, whereas 63% made decisions on the basis of weed problems from previous years. Most respondents (88%) expressed moderate to high concern for herbicide-resistant weeds in their operations. Strategies to manage herbicide-resistant weeds and economical weed management practices were among the top suggested research needs. The field survey revealed that jungle rice, Nealley’s sprangletop, and hemp sesbania were the top three late-season weed escapes in rice production in Texas, with frequencies of occurrence of 28%, 19%, and 13%, respectively. Furthermore, average field area infested by a species was the greatest for jungle rice (13%), followed by hemp sesbania (11%) and weedy rice (11%). Findings from the stakeholder and field surveys help direct future research and outreach efforts for sustainable weed management in Texas rice.