Postemergence (POST) herbicides that control troublesome weeds during hybrid bermudagrass establishment via sprigs are limited due to potential turfgrass phytotoxicity and herbicide-resistant weeds. Research experiments were conducted in Blacksburg, VA, and Hope, AR, in 2016 and 2023 to evaluate herbicide programs to control goosegrass and smooth crabgrass and the response of hybrid bermudagrass sprigs to POST herbicides applied 3 to 5 wk after establishment (WAE). Another study was conducted to assess the tolerance of ‘Latitude 36’, ‘Tahoma 31’, and ‘TifTuf’ hybrid bermudagrass sprigs to POST herbicides applied 4 to 5 WAE. Thiencarbazone + foramsulfuron + halosulfuron did not injure hybrid bermudagrass > 6% across four cultivars and a total of 10 site-yr but reduced goosegrass and smooth crabgrass cover equivalent to the best-performing treatments. Topramezone + metribuzin injured turfgrass > 25% at 14 d after treatment (DAT), but tank mixing with thiencarbazone + foramsulfuron + halosulfuron reduced injury by 5% to 22%. Quinclorac injured hybrid bermudagrass 17% to 58%, depending on site, which was more than most other treatments. Mesotrione-, quinclorac-, or topramezone-based programs injured hybrid bermudagrass and also reduced turfgrass cover, the dark green color index, and the normalized difference vegetation index, but turfgrass recovered by 28 DAT. Results suggest that turfgrass managers have a variety of herbicides that can control smooth crabgrass and goosegrass during hybrid bermudagrass sprig establishment, but the margin of selectivity is relatively low for mesotrione, quinclorac, and topramezone and may be dependent on herbicide rate or hybrid bermudagrass cultivar.

Two separate field studies were conducted at two locations near Crowley, Louisiana, to evaluate early season applications of florpyrauxifen and a prepackaged mixture of halosulfuron plus prosulfuron in water-seeded rice production. In each study, florpyrauxifen and halosulfuron plus prosulfuron were applied at two rates and either applied to the soil surface 48 h before the seeding flooding and seeding, directly onto the pregerminated seed 24 h following seeding and immediately after removal of the seeding flood (SEED), and at pegging. Data suggest that both florpyrauxifen and halosulfuron plus prosulfuron have a role to play in water-seeded rice production. Crop injury of 19% was observed from applications of florpyrauxifen applied directly to pregerminated SEED. Additionally, 28% crop injury was observed when halosulfuron plus prosulfuron was applied directly to SEED. Due to crop injury observations, both herbicides should be avoided when the pregerminated seed is exposed to the soil surface after removing the seeding flood. These data suggest that florpyrauxifen may be a better option for postemergence application, whereas halosulfuron plus prosulfuron may be a better preemergence option in water-seeded rice production. Overall, the findings show that both herbicide technologies will provide adequate early-season weed control in water-seeded rice production.

Weed management in cantaloupe and other melon crops is important to maximize fruit yield; however, there are few registered herbicides available in California. Several independent herbicide trials were conducted at University of California field stations in Davis (Yolo County), Five Points (Fresno County), and Holtville (Imperial County) from 2013 to 2019 to evaluate both registered and unregistered herbicides and incorporation methods (sprinklers, cultivation, or none) for crop safety and weed control in melons. Although specific treatments varied among locations depending on local practice and research objectives, ethalfluralin and halosulfuron were used in all experiments, and bensulide and S-metolachlor were evaluated in 4 of 6 site-years. Additional herbicides included clethodim, clomazone, DCPA, napropamide, pendimethalin, sethoxydim, and sulfentrazone. Among registered herbicides, halosulfuron, halosulfuron + ethalfluralin, and ethalfluralin + bensulide combinations provided consistently beneficial weed control across all site-years compared to the nontreated control. S-metolachlor performed as well as the best of the registered herbicides tested at each site-year; although moderate injury was noted at the Davis location, this did not reduce melon yield. The method used to incorporate preplant herbicides had a significant impact on weed control efficacy but varied by location. Mechanical incorporation of preplant herbicides resulted in improved weed control and yield compared to sprinklers. Early-season weed control, whether by herbicides or hand weeding, resulted in significant yield increase in most site-years.

Laboratory and greenhouse studies were conducted to evaluate the effects of chemical treatments applied to Palmer amaranth seeds or gynoecious plants that retain seeds to determine seed germination and quality. Treatments applied to physiologically mature Palmer amaranth seed included acifluorfen, dicamba, ethephon, flumioxazin, fomesafen, halosulfuron, linuron, metribuzin, oryzalin, pendimethalin, pyroxasulfone, S-metolachlor, saflufenacil, trifluralin, and 2,4-D plus crop oil concentrate applied at 1× and 2× the suggested use rates from the manufacturer. Germination was reduced by 20% when 2,4-D was used, 15% when dicamba was used, and 13% when halosulfuron and pyroxasulfone were used. Use of dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D resulted in decreased seedling length by an average of at least 50%. Due to the observed effect of dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D, these treatments were applied to gynoecious Palmer amaranth inflorescence at the 2× registered application rates to evaluate their effects on progeny seed. Dicamba use resulted in a 24% decrease in seed germination, whereas all other treatment results were similar to those of the control. Crush tests showed that seed viability was greater than 95%, thus dicamba did not have a strong effect on seed viability. No treatments applied to Palmer amaranth inflorescence affected average seedling length; therefore, chemical treatments did not affect the quality of seeds that germinated.

Herbicide management information is lacking for recently developed turf-type bahiagrass germplasm. The objective of this study was to evaluate the herbicide tolerance of nine experimental bahiagrass genotypes compared to the industry standard ‘Argentine’. The experimental entries included Argentine and ‘Wilmington’ mutants, and wild-type breeding lines. Plants were grown under greenhouse conditions, and 12 herbicides were applied at 1× and 2× labeled rates. Bentazon, bromoxynil, carfentrazone + 2,4-D + MCPP + dicamba, and carfentrazone were classified as safe. Fluroxypyr, halosulfuron, and triclopyr + clopyralid reduced growth >50% when applied at twice the label rate. Fenoxaprop, sulfentrazone + imazethapyr, and thiencarbazone + iodosulfuron + dicamba reduced growth and caused turfgrass injury above an acceptable threshold (≥20%). In general, the Argentine mutants showed greater herbicide injury compared to the Wilmington mutants. However, metsulfuron exceeded the acceptable injury threshold and stopped growth in all the genotypes, Argentine and genotype WT6 were the least injured by this herbicide. The experimental genotype WT6 consistently showed the greatest herbicide tolerance. Except for one genotype (WT4), the experimental genotypes responded similarly or better than Argentine to the tested herbicides, except for metsulfuron.

Yellow nutsedge is one of the most widely distributed and troublesome weeds in the world. Field and greenhouse studies were conducted to optimize strategies for increased yellow nutsedge control in turfgrass with halosulfuron and sulfentrazone. In the field study in yellow nutsedge and perennial ryegrass mixture, single or sequential applications (3 wk after initial) of halosulfuron or sulfentrazone were made on June 3, June 23, July 15, or August 5 in 2013, 2014, 2015, and 2016. Percent yellow nutsedge control was rated within the same growing season on September 17 and the following year on June 3 for carryover control. Field and greenhouse studies confirm that sequential applications of halosulfuron with a 3-wk interval resulted in >95% control in a yellow nutsedge–turfgrass mixture. In a greenhouse study, both herbicides reduced yellow nutsedge root and rhizome dry mass from 39% to 98%, reduced number of new tubers and tuber fresh weight from 38% to 100%, and prevented re-emergence. Sequential applications of either herbicide within a 3-wk interval early postemergence is recommended for optimal control. Herbicide application to yellow nutsedge using halosulfuron and sulfentrazone should be made as early as possible postemergence, preferably at the three- to five-leaf stage or 200 to 250 growing degree days (GDD, 10 C base). Mowing can be an effective method to reduce yellow nutsedge growth. Mowing at 7.6 cm weekly reduced yellow nutsedge rhizome dry mass by 55% and number of new tubers formed by 63% in the greenhouse study. Physical removal of yellow nutsedge plants such as hand-pulling can be an effective method to manage yellow nutsedge and is most effective at the three- to five-leaf stage (200 to 250 GDD). End-users can maximize yellow nutsedge control by integrating early herbicide treatments and cultural practices such as mowing and hand-pulling.

A field study was conducted in 2017 and 2018 at the Louisiana State University Agricultural Center H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the impact of reduced rates of halosulfuron on quizalofop activity in Louisiana rice production. Halosulfuron and a prepackaged mixture of halosulfuron plus thifensulfuron were evaluated at 0, 17, 35, or 53 g ai ha−1 and 34 or 53 g ai ha−1, respectively, in a mixture with quizalofop at 120 g ai ha−1. Control of barnyardgrass, red rice, and two non-acetyl-CoA carboxylase resistant rice lines, CL-111 and CLXL-745, were recorded at 14 and 28 d after treatment (DAT). The red rice, CL-111, and CLXL-745 represented a weedy rice population. Across all species evaluated at 14 DAT, all mixtures containing halosulfuron and halosulfuron plus thifensulfuron resulted in antagonism with an observed control of 79% to 90%, compared with an expected control of 96% to 99%. At 28 DAT, all mixtures containing halosulfuron resulted in neutral interactions for barnyardgrass control. Quizalofop mixed with halosulfuron plus thifensulfuron at the lower rate of 34 g ha−1 was able to overcome the antagonism compared with the higher rate of 53 g ha−1 for barnyardgrass control at 28 DAT. Both the high and the low rate of halosulfuron plus thifensulfuron resulted in antagonistic interaction for red rice, CL-111, and CLXL-745 control at 28 DAT. This research suggests that mixing quizalofop with halosulfuron plus thifensulfuron should be avoided, especially at the higher rate of 53 g ha−1.

Purple nutsedge is a troublesome weed in tomato grown in plasticulture systems. Field trials were conducted in the fall of 2017 and spring of 2018 at Balm, FL, to evaluate multiple herbicide programs applied pretransplanting (pre-T), post-transplanting (post-T), and pre-T followed by (fb) post-T for purple nutsedge control in plasticulture tomato. Pre-T treatment of sulfentrazone or S-metolachlor alone were ineffective and did not decrease purple nutsedge density compared with the nontreated control. Post-T application of halosulfuron did not reduce purple nutsedge density at 12 wk after initial treatment (WAIT) in fall 2017 but reduced the purple nutsedge density at 17 WAIT in both seasons. Pre-T sulfentrazone or S-metolachlor application fb halosulfuron applied post-T were the most effective treatments and consistently reduced purple nutsedge population in both seasons. Herbicide treatments did not injure or reduce tomato height or yield. Overall, these results suggest sequential herbicide programs, including pre-T application of sulfentrazone or S-metolachlor fb post-T application of halosulfuron generally resulted in greater purple nutsedge control compared with pre-T or post-T application only. Halosulfuron applied post-T is critical to provide season-long purple nutsedge control in plasticulture tomato.

Nutsedge species are problematic in plastic-mulched vegetable production because of the weed’s rapid reproduction and ability to penetrate the mulch. Vegetable growers rely heavily on halosulfuron to manage nutsedge species; however, the herbicide cannot be applied over mulch before vegetable transplanting due to potential crop injury. This can be problematic when multiple crops are produced on a single mulch installation. Field experiments were conducted to determine the response of broccoli, cabbage, squash, and watermelon to halosulfuron applied on top of mulch prior to transplanting. Halosulfuron at 80 g ai ha−1 was applied 21, 14, 7, and 1 d before planting (DBP), and 160 g ai ha−1 was applied 21 DBP. In all experiments, extending the interval between halosulfuron application and planting reduced crop injury. For squash and watermelon, visual injury, plant diameters/vine runner lengths, marketable fruit weights, and postharvest plant biomass resulted in similar values when applying 80 g ha−1 21 DBP and with the nontreated weed-free control. Reducing this interval increased injury for both crops. Visual crop injury and yield reductions up to 40% occurred, with halosulfuron applied 14, 7, or 1 DBP in squash and 1 DBP in watermelon. Broccoli and cabbage showed greater sensitivity, with injury and plant diameter reductions greater than 15%, even with halosulfuron applied at 80 g ha−1 21 DBP. Experimental results confirm that halosulfuron binds to plastic mulch, remains active, and is slowly released from the mulch over a substantial period, during rainfall or overhead irrigation events. Extending the plant-back interval to at least 21 d before transplanting did overcome squash and watermelon injury concerns with halosulfuron at 80 g ha−1, but not broccoli and cabbage. Applying halosulfuron over mulch to control emerged nutsedge before planting squash and watermelon would be beneficial if adequate rainfall or irrigation and appropriate intervals between application and planting are implemented.

Living mulches can provide many sustainability benefits. However, living mulch–cash crop competition and unreliable weed control are major challenges in living mulch systems. In this study, we evaluated the potential of herbicides used at reduced rates in combination with living mulch to suppress weeds, while simultaneously reducing living mulch vigor. Herbicide treatments were a combination of two POST applications, each consisting of a single, different herbicide. Field trials were conducted in Freeville, NY, USA, using: fresh market field tomato as cash crop; sesbania and sunn hemp as living mulch; and the herbicides fomesafen, halosulfuron, metribuzin, and rimsulfuron. In 2015, when water was not limiting, tomato yield and living mulch biomass were positively correlated. This relationship was negative in 2016, likely because of drought during the growing season. Compared with the untreated living mulch check, using the herbicide treatments in combination with living mulch reduced tomato yield losses by up to 71% in 2015 and 51% in 2016. In these herbicide plus living mulch plots, weed biomass was reduced by up to 97%, compared with the weedy check. Living mulch in herbicide treatments generated up to 2500 kg ha−1 of dry matter during both 2015 and 2016, with an average ground cover of 63% in 2015 and 85% in 2016. A predominantly PRE herbicide with residual soil activity (metribuzin), followed by a herbicide with greater POST activity (halosulfuron/rimsulfuron) was the most effective herbicide application sequence. Results from our study indicate that well-designed herbicide applications may enhance the practicability of living mulch systems.

Residual herbicides are routinely applied to control troublesome weeds in pumpkin production. Fluridone and acetochlor, Groups 12 and 15 herbicides, respectively, provide broad-spectrum PRE weed control. Field research was conducted in Virginia and New Jersey to evaluate pumpkin tolerance and weed control to PRE herbicides. Treatments consisted of fomesafen at two rates, ethalfluralin, clomazone, halosulfuron, fluridone, S-metolachlor, acetochlor emulsifiable concentrate (EC), acetochlor microencapsulated (ME), and no herbicide. At one site, fluridone, acetochlor EC, acetochlor ME, and halosulfuron injured pumpkin 81%, 39%, 34%, and 35%, respectively, at 14 d after planting (DAP); crop injury at the second site was 40%, 8%, 19%, and 33%, respectively. Differences in injury between the two sites may have been due to the amount and timing of rainfall after herbicides were applied. Fluridone provided 91% control of ivyleaf morningglory and 100% control of common ragweed at 28 DAP. Acetochlor EC controlled redroot pigweed 100%. Pumpkin treated with S-metolachlor produced the most yield (10,764 fruits ha–1) despite broadcasting over the planted row; labeling requires a directed application to row-middles. A separate study specifically evaluated fluridone applied PRE at 42, 84, 126, 168, 252, 336, and 672 g ai ha–1. Fluridone resulted in pumpkin injury ≥95% when applied at rates of ≥168 g ai ha–1; significant yield loss was noted when the herbicide was applied at rates >42 g ai ha–1. We concluded that fluridone and acetochlor formulations are unacceptable candidates for pumpkin production.

Reductions in MSMA use for weed control in turfgrass systems may have led to increased common carpetgrass infestations. The objective of our research was to identify alternative POST herbicides for control of common carpetgrass using field and controlled-environment experiments. Field applications of MSMA (2.2 kg ai ha−1) and thiencarbazone + iodosulfuron + dicamba (TID) (0.171 kg ai ha−1) resulted in the greatest common carpetgrass control 8 wk after initial treatment (WAIT): 94% and 91%, respectively. Thiencarbazone + foramsulfuron + halosulfuron (TFH) (0.127 kg ai ha−1) applied in the field resulted in 77% control 8 WAIT, whereas all other treatments were ≤19% effective at 8 WAIT. All treatments resulted in greater common carpetgrass control when applied in the greenhouse. Applications of MSMA, TFH, and TID resulted in the highest common carpetgrass control in the greenhouse 8 WAIT: 94%, 94%, and 91%, respectively. Control with nicosulfuron (0.035 kg ai ha−1) and trifloxysulfuron (0.028 kg ai ha−1) (81% and 75%, respectively) was greater in the greenhouse than observed in the field 8 WAIT. Sequential applications of foramsulfuron (0.058 kg ai ha−1) resulted in only ≤11% common carpetgrass control 8 WAIT, regardless of application site. All herbicide treatments in the greenhouse resulted in reduced aboveground common carpetgrass biomass 8 WAIT compared to the nontreated control (12.9 g). Aboveground biomasses of common carpetgrass in response to MSMA, TID, TFH, nicosulfuron, and trifloxysulfuron were 1.6 to 2.1 g, regardless of treatment. Reduced efficacy of foramsulfuron was reflected in greater biomass (4.7 g) in response to treatments. Thiencarbazone + iodosulfuron + dicamba may be an alternative to MSMA for common carpetgrass control; however, long-term assessment may be warranted to evaluate treatment effectiveness. Further investigation into application timing may be necessary to enhance the efficacy of TFH for the control of common carpetgrass.

A study was conducted at the Louisiana State University Agricultural Center’s H. Rouse Caffey Rice Research Station in 2017 and 2018 to evaluate a prepackaged mixture of clomazone plus pendimethalin applied delayed preemergence (DPRE) or POST within an herbicide residual overlay with saflufenacil, clomazone, or quinclorac. POST applications included penoxsulam or halosulfuron in combination with the second residual application. No differences were observed in barnyardgrass control (92% to 98%) at 14 days after treatment (DAT). At 42 DAT, barnyardgrass treated with clomazone plus pendimethalin in combination with either clomazone or quinclorac at either timing was controlled 95% to 96%. However, when saflufenacil was applied PRE, regardless of the POST herbicide or when saflufenacil was applied POST with halosulfuron, barnyardgrass control was reduced to 78% to 81%, compared with 95% to 96% with the control with all other residual combinations. Yellow nutsedge and rice flatsedge control increased when treated with halosulfuron compared with penoxsulam across all evaluation dates. At 28 and 42 DAT, texasweed treated with saflufenacil PRE, regardless of POST applications, was controlled 83% and 87%, respectively, and this was greater control than provided by clomazone or quinclorac applied PRE regardless of POST herbicide program.

Herbicides are the foundation for row-middle weed control in Florida plasticulture production. Paraquat is commonly used as a burndown herbicide, and resistance issues have subsequently developed. Halosulfuron is mixed with PRE and POST herbicides to provide additional control of nutsedge. The objective of the study was to determine glufosinate efficacy on weeds emerging in the row-middle and suitability in mixture with halosulfuron for nutsedge control. For total weed control, the high dose of glufosinate (983 g ai ha–1) gave the highest overall control (98% and 64% at 4 wk after treatment for experiments 1 and 2, respectively), and the low rate of glufosinate (656 g ha–1) (67% and 39%) gave results comparable to paraquat (57% and 44%). The high glufosinate dose and paraquat gave comparable control of Brazil pusley (74% to 77% control). Glufosinate + halosulfuron mixture had lower efficacy on Brazil pusley than halosulfuron + paraquat mixture. Glufosinate application reduced grass densities, whereas paraquat did not. Increasing the glufosinate dose did not further decrease grass densities. Similar trends in grass control were also demonstrated in their respective mixtures. Mixing halosulfuron with glufosinate or paraquat did not provide consistent reductions in nutsedge densities, nor did adding paraquat or glufosinate further reduce densities compared with halosulfuron alone for the 4-wk study period. Both paraquat and glufosinate antagonized halosulfuron and reduced efficacy on nutsedge. Compared to controls, there was a reduction between expected and actual nutsedge control for paraquat and glufosinate (25% and 36%), respectively. For total weed control, glufosinate is a suitable alternative to paraquat for row-middle weed management in vegetable production.

A 3-yr watermelon experiment was established in fall 2013 to evaluate cover crop, polyethylene mulch, tillage, and herbicide application components for weed control, yield, and profitability. Conservation tillage, either with a cereal rye cover crop alone or integrated with polyethylene mulch, was compared to the standard industry practice of conventional tillage with bedded polyethylene mulch. The study also used a non-bedded conventional tillage system without polyethylene to determine polyethylene and cover crop residue effects. Within each of the four systems, herbicide treatments comprised halosulfuron applied (1) at 26.3 g ai ha–1 PRE, (2) at 26.3 g ai ha–1 POST, or (3) sequentially at 26.3 g ai ha–1 PRE and POST. Each system also had a nontreated control. In addition, clethodim was applied in all plots twice POST at 140 g ai ha–1, except for nontreated in each system. In 2014, polyethylene or cereal rye cover crop effectively controlled tall morningglory, coffee senna, and carpetweed early season in nontreated plots, whereas the integration of the two was effective at controlling common purslane. Tall morningglory and purslane control was insufficient late season regardless of production system and herbicide application. In 2015, polyethylene effectively controlled cutleaf eveningprimrose, sicklepod, and arrowleaf sida early season in nontreated plots. Yellow nutsedge control was insufficient late season regardless of production system and herbicide application. Utilizing sequential halosulfuron applications did not increase weed control over PRE or POST alone in all years. Polyethylene use resulted in yields higher than systems without in all years. Across all 3 yr, net returns were highest for polyethylene mulch systems. The results of this experiment underscore the need for more progress in developing integrated conservation systems for watermelon production. Effective herbicides, low-disturbance cultivation, and/or hand weeding are most likely the key to success in conservation specialty crop systems.

Control of broadleaf weeds in caladium is difficult due in part to a lack of selective POST herbicides. Cultivation is not an option due to the dense canopy and potential for tuber injury. As a result, growers currently rely on preemergence (PRE) herbicide and hand-weeding. The objective of this research was to evaluate the control of four common broadleaf weeds of field grown caladium with POST applications of halosulfuron, thifensulfuron-methyl, and trifloxysulfuron, and determine the tolerance of caladium cultivars ‘Florida Fantasy’ and ‘Florida cardinal’ to POST applications of halosulfuron. At 4 weeks after treatment (WAT), thifensufluron-methyl at 28 g ai ha−1 and trifloxysulfuron at 84 g ai ha−1 provided approximately 90 and 70% common purslane control, respectively, while halosulfuron at 210 g ai ha−1 provided 55% suppression. Trifloxysulfuron controlled ≥90% spotted spurge at 42 g ha−1, whereas the highest rate of halosulfuron and thifensulfuron-methyl only achieved 60% suppression. In field experiments, the evaluated sulfonylurea (SU) herbicides were less efficacious on hairy indigo and sharppod morningglory as control never exceeded 65 and 50%, respectively. In greenhouse experiments, the evaluated halosulfuron rates ranging from 26 to 420 g ha−1 did not significantly reduce caladium tuber weight from the nontreated control. Averaged over halosulfuron rates, ‘Florida Fantasy’ damage was 5 and 6% at 2 and 4 WAT, respectively, while ‘Florida Cardinal’ damage was 11%. We conclude that none of the herbicide treatments effectively controlled all species evaluated. Sequential treatments, higher rates, or tank-mixtures may be necessary to adequately control these species. We also conclude that caladium cultivars ‘Florida Fantasy’ and ‘Florida Cardinal’ have acceptable tolerance to POST applications of halosulfuron. Further research is needed to evaluate caladium tolerance to other SU herbicides.

Tropical signalgrass (TSG) is one of the most problematic weeds found on golf courses, sports fields, and sod farms in south Florida. The recent ban of monosodium methane-arsonate (MSMA), an organic arsenical herbicide, from urban areas in Florida has left turfgrass managers searching for effective management options. In an effort to avoid relying solely on POST chemical control, this research examined the effect of combining a cultural practice, verticutting, along with PRE and POST herbicides as an integrated weed management approach to controlling TSG in hybrid bermudagrass. Field experiments were conducted at multiple locations over 2 yr in south Florida to: (1) determine whether verticutting before herbicide applications increases TSG control and (2) identify herbicide programs that effectively control TSG. No interactions between verticutting and herbicide programs were detected, but verticutting consistently provided a slight reduction (8% averaged across herbicide treatments) in TSG cover. Treatments containing a PRE herbicide resulted in a significant reduction (20% to 50%) in TSG cover at 52 wk after initial treatment (WAIT), while some POST herbicide treatments reduced TSG cover to <20% at 52 WAIT. A study was conducted to determine which POST herbicide combinations were most efficacious in controlling TSG. Amicarbazone alone provided ≤35% TSG control at 8 and 12 WAIT, but synergistic responses were observed between amicarbazone and mesotrione, trifloxysulfuron, and thiencarbazone+foramsulfuron+halosulfuron. Two- and three-way combinations of amicarbazone with these POST herbicides resulted in >80% TSG control at 4, 8, and 12 WAIT, with some reaching 100% TSG control at 4 WAIT. Based on these data, verticutting may provide limited complementary control, but certain combinations of POST herbicides exhibited excellent (>95%) TSG control.

A field study was conducted in 2015 and 2016 at the H. Rouse Caffey Rice Research Station (RRS) to evaluate antagonistic, synergistic, or neutral interactions of quizalofop when mixed with ALS-inhibiting herbicides labeled in rice production. Quizalofop was applied at 120 g ai ha−1. Mixture herbicides included penoxsulam at 40 g ai ha−1, penoxsulam+triclopyr at 352 g ai ha−1, halosulfuron at 53 g ai ha−1, bispyribac at 34 g ai ha−1, orthosulfamuron+halosulfuron at 94 g ai ha−1, orthosulfamuron+quinclorac at 491 g ai ha−1, imazosulfuron at 211 g ai ha−1, and bensulfuron at 43 g ai ha−1. All ALS herbicides mixed with quizalofop indicated antagonistic responses for red rice, CL-111, CLXL 745, or barnyardgrass control at either 14 or 28 days after treatment (DAT). At 28 DAT, quizalofop mixed with penoxsulam or bispyribac controlled barnyardgrass 34 to 38%, compared with an expected control of 97%. In addition, these same mixtures controlled red rice, CL-111, and CLXL-745 61 to 67% at 28 DAT compared with an expected control of 96 to 97%. A second application of quizalofop at 120 g ha−1 was applied at 28 DAT. At 42 DAT, neutral responses were indicated for all mixtures except with quizalofop mixed with penoxsulam containing products.

Purple nutsedge is difficult to control in vegetable plasticulture due to its ability to penetrate the plastic mulch. Experiments were conducted in Spring 2011 and 2012 at the Plant Science Research and Education Center in Citra, Florida, and in Spring and Fall 2013 at the Gulf Coast Research and Education Center in Balm, Florida. The objective was to determine tomato (cv. Amelia, Charger, and Florida 47) tolerance and purple nutsedge response to herbicides and herbicide tank-mixes applied POST-directed to base of tomato. Chlorimuron-ethyl, flazasulfuron, fomesafen, halosulfuron, imazosulfuron, rimsulfuron, nicosulfuron, and trifloxysulfuron applied POST-directed to the base of the crop did not cause crop damage. Halosulfuron or tank-mixes that contained halosulfuron tended to provide the greatest nutsedge suppression in all experiments. Halosulfuron or nicosulfuron+rimsulfuron applications when tomato (cv. Charger) were flowering reduced marketable yields by 22-28% compared to the nontreated control. No yield reductions occurred with Florida 47 or Amelia cultivars. Flazasulfuron provided similar purple nutsedge suppression to halosulfuron and did not damage tomato. Tank-mixes that contained halosulfuron tended not to provide any added benefit over halosulfuron alone. This research identified herbicides that are safe for use as a POST-directed application in tomato. Additional research is needed to evaluate efficacy of these herbicides on broadleaf weeds.

Palmer amaranth, a dioecious summer annual weed species, is the most troublesome weed in agronomic crop production systems in the United States. Palmer amaranth resistant to photosystem (PS) II- and 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors is of particular concern in south central Nebraska. The objectives of this study were to determine the effect of PRE followed by POST herbicide programs on PS II- and HPPD-inhibitor-resistant Palmer amaranth control, crop yield, and net economic return in conventional corn. A field study was conducted in 2014, 2015, and 2016 in a grower’s field infested with PS II- and HPPD-inhibitor-resistant Palmer amaranth near Shickley in Fillmore County, Nebraska. A contrast analysis suggested that mesotrione+S-metolachlor+atrazine applied PRE provided 83% Palmer amaranth control at 21 d after application compared to 78 and 72% control with pyroxasulfone+fluthiacet-ethyl+atrazine and saflufenacil+dimethenamid-P, respectively. Most of the PRE followed by POST herbicide programs provided ≥85% Palmer amaranth control. Based on contrast analysis, POST application of dicamba+diflufenzopyr provided 93% Palmer amaranth control compared to 87, 79, and 42% control with dicamba, dicamba+halosulfuron, and acetochlor, respectively, at 28 d after POST. All PRE followed by POST herbicide programs, aside from mesotrione+S-metolachlor+atrazine followed by acetochlor (2,530 to 7,809 kg ha−1), provided 9,550 to 10,500 kg ha−1 corn yield compared with 2,713 to 6,110 kg ha−1 from nontreated control. Similarly, PRE followed by POST herbicide programs, except for mesotrione+S-metolachlor+atrazine followed by acetochlor ($191 and $897 ha−1), provided similar net return of $427 to $707 ha−1 and $1,127 to $1,727 ha−1 in 2014 and 2015-16, respectively. It is concluded that herbicide programs based on multiple sites of action are available for control of PS II- and HPPD-inhibitor-resistant Palmer amaranth in conventional corn.