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The use of Enlist®, XtendFlex®, and LibertyLink® cropping systems are effective tools to facilitate weed management in cotton (Gossypium hirsutum L.). These technologies enable farmers to use 2,4-D, dicamba, or glufosinate over the top of cotton in season. However, the incidence of Palmer amaranth (Amaranthus palmeri S. Wats.) escapes demonstrates the importance of surveilling the spread of herbicide resistance. Therefore, this study aimed to evaluate herbicide resistance in Palmer amaranth accessions collected after glufosinate and auxin mimic herbicides (2,4-D or dicamba) were applied for weed control. A total of 22 accessions from eastern Arkansas were collected in the 2021 growing season. Herbicide treatments were equivalent to 0.5× or 1× rate of 2,4-D (Enlist One®) at 0.48 and 0.95 lb ae/ac, dicamba (XtendiMax®) at 0.25 and 0.5 lb ae/ac, and glufosinate (Liberty®) at 0.29 and 0.58 lb ai/ac, respectively. All treatments were applied to greenhouse-grown Palmer amaranth plants with 5 to 6 leaves, and 2 runs of 50 plants per accession were sprayed per treatment. Plant mortality (%) was assessed 21 days after treatment. Treatments with 2,4-D, dicamba, and glufosinate at 0.5× resulted in 80% or less mortality to 18, 13, and 6 accessions, respectively. Treatments with a 1× rate provided more than 80% control to all accessions treated with dicamba; meanwhile, only 18 and 21 accessions treated with 2,4-D and glufosinate, respectively, resulted in the same level of mortality. 2 accessions that resulted in less than 60% mortality after treatment with a 1× rate of 2,4-D were further evaluated, and resistance to 2,4-D was confirmed. These findings demonstrate the importance of monitoring weed survival in production fields. Implementing integrated weed management strategies to reduce selective pressure over current herbicide options could help mitigate herbicide resistance cases. [ABSTRACT FROM AUTHOR]

Resistance to glufosinate in Palmer amaranth (Amaranthus palmeri S. Wats.) was first reported in 2021 in Arkansas. Alternative chemical control methods are highly sought to avoid the spread of this problematic herbicide-resistant weed across the southern region of the United States. This study aimed to determine the effectiveness of herbicides labeled for preplant or preemergence applications in cotton (Gossypium hirsutum L.) and soybean (Glycine max L.) to control glufosinate-resistant Palmer amaranth. The preemergence (PRE) treatments were imazaquin (0.12 lb ai/ac), pendimethalin (1 lb ai/ac), diuron (1 lb ai/ac), metribuzin (0.67 lb ai/ac), flumioxazin (0.063 lb ai/ac), saflufenacil (0.045 lb ai/ac), fomesafen (0.25 lb ai/ac), trifludimoxazin (0.045 lb ai/ac), acetochlor (1.124 lb ai/ac), S-metolachlor (1.24 lb ai/ac), pyroxasulfone (0.129 lb ai/ac), and fluridone (0.15 lb ai/ac). Irrigation in the amount of 1 inch was applied after application to ensure the activation of herbicides. A postemergence (POST) treatment with glufosinate at 0.585 lb ai/ac was applied twenty days after preemergence treatments to confirm the presence of a glufosinate-resistant accession in the trial site. A randomized complete block design with 4 replicates was used with a nontreated control for comparison. Visual control (%) was rated, and aboveground biomass was collected 6 weeks after PRE treatments. Biomass reduction (%) was calculated in comparison to the nontreated control. The lowest visual control and biomass reduction were observed in treatments that received only glufosinate POST or imazaquin preemergence due to resistance to these herbicides. Low control and biomass reduction were also detected following the treatment with pendimethalin. Besides the herbicides mentioned above, visual control and biomass reduction rates were similar for all other herbicides. Although most of the tested herbicides provided acceptable Palmer amaranth control, overlapping multiple effective residual herbicides and POST-applied options are crucial to controlling glufosinate-resistant populations. [ABSTRACT FROM AUTHOR]

Diflufenican is a new herbicide to be labeled, potentially, for soybean [Glycine Max (L.) Merr] production in the United States. Diflufenican is an Herbicide Resistance Action Committee/Weed Science Society of America group 12 herbicide, the first group 12 herbicide labeled for use in soybean production. Soybean producers need new chemistries to help control Palmer amaranth (Amaranthus palmeri S. Wats.). Palmer amaranth has evolved resistance to 9 modes of action; therefore, diflufenican is being evaluated for its control. Two field experiments were conducted at the University of Arkansas System Division of Agriculture's Milo J. Shult Agricultural Research and Extension Center in Fayetteville, Arkansas, to evaluate the tolerance of soybean and associated weed control with various rates and application timings of the diflufenican mixture. For the tolerance trial, the diflufenican mixture was applied at 1 and 2 times the anticipated 1X labeled rates at 14- and 7-day preplant, preemergence, and 3 days after planting (DAP). The diflufenican mixture was applied 14- and 7-day preplant, preemergence, and 3 DAP at a 1X labeled rate for the weed control trial. Injury 14 DAP ranged from 2% to 20% for the 1X rate of the herbicide and 6% to 32% for the 2X rate. By 28 DAP, injury decreased for both herbicide rates, with the most injury being observed at the 3 DAP application timing for both rates. Grain yield was collected at maturity, and no difference was observed between application timings and herbicide rates. Palmer amaranth and common lambsquarters (Chenopodium album L.) control was greater than 97% for all application timings, except the 14-day preplant timing 21 DAP. By 42 DAP, the application timing of preemergence and 3 DAP provided greater than or equal to 90% control of the 2 weeds. Grain yield increased the closer the herbicide application was made to planting and soybean emergence due to improved weed control. [ABSTRACT FROM AUTHOR]

Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] has become more problematic and difficult to control because it is resistant to multiple herbicides. Fall-applied residual herbicides have effectively controlled other winter annual weeds and could be another option in controlling Italian ryegrass. The objective of this study was to evaluate multiple residual herbicides for the control of Italian ryegrass in the fall and the following spring before planting soybean [Glycine max (L.) Merr.]. Before any weed emergence, a field experiment was initiated at the University of Arkansas System Division of Agriculture's Jackson County Extension Center near Newport, Ark., in the fall of 2021. Treatments in this experiment consisted of Anthem® Flex (4 fl oz/ac), Command® (20 fl oz/ac), Dual Magnum® (1.33 pt/ac), Outlook® (16 fl oz/ac), Prowl® (2.1 pt/ac), Treflan® (2 pt/ac), Warrant® (2.5 pt/ac), Warrant® (5 pt/ac), and Zidua® SC (3.75 fl oz/ac). Initial visual control of Italian ryegrass 14 days after application (DAA) (28 Oct. 2021) exceeded 95% for every herbicide treatment except for Prowl and the low rate of Warrant. Only Zidua SC, Anthem Flex, and Dual Magnum retained effective residual control at 60 DAA (13 Dec. 2021) (>95%) and 166 DAA (29 March 2022) (>90%). Overall, using Zidua SC, Anthem Flex, and Dual Magnum herbicides were the most effective options to control Italian ryegrass in the fall and following spring before planting soybean. These fall-applied treatments would improve overall Italian ryegrass management and delay the evolution of resistance to postemergence herbicides. [ABSTRACT FROM AUTHOR]

Palmer amaranth (Amaranthus palmeri S. Watson), commonly known as Palmer pigweed, is problematic for soybean production throughout the mid-South. Palmer amaranth rapidly evolves resistance to herbicides; thus, alternative management tools are urgently needed. This project focused on identifying, optimizing, and commercializing bioherbicides derived from naturally occurring Palmer amaranth pathogens. In previous work, we identified 2 fungal pathogens (isolates AF22 and AF24) that were highly virulent on juvenile and adult Palmer amaranth plants. In the current study, we created a novel competition screen to identify additional candidate bioherbicide organisms. Seventy-seven taxonomically diverse Palmer amaranth pathogens (strains PWA1-PWA77) were applied simultaneously to soil containing germinating pigweed seeds. Pathogens were re-isolated from diseased pigweed seedlings, and their virulence on adult pigweed plants was evaluated individually. Strain PWA43 and re-isolated strains PWA78, PWA87, PWA98, and PWA110 consistently ranked among the most virulent strains in multiple assays. Morphologically, all 5 strains were highly similar, suggesting that PWA78, PWA87, PWA98, and PWA110 were re-isolations of strain PWA43. The genomes of strains PWA43 and PWA98 were sequenced and analyzed, which confirmed that PWA98 was a re-isolation of PWA43. PWA43 represents a novel bioherbicide candidate taxonomically distinct from previously identified candidates AF22 and AF24. The genomic resources created in this study will accelerate the optimization and commercial development of PWA43 as a bioherbicide for Palmer amaranth. [ABSTRACT FROM AUTHOR]

In a flooded Arkansas rice system, producers and consultants identified the most problematic weed they face is barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.]. Due to the evolution of herbicide resistance and the overall hardiness of the weed, other control measures are needed for barnyardgrass in rice. The objective of this study was to evaluate the influence of rice cultivars and the manipulation of drill row width for barnyardgrass control in rice. Field experiments were conducted at the University of Arkansas System Division of Agriculture's Pine Bluff Small Farm Outreach Center, near Lonoke, Arkansas, Pine Tree Research Station, near Colt, Arkansas, and the Rohwer Research Station, near Watson, Arkansas in 2021 and 2022. The experiments were designed as randomized complete block split-plot designs (16 treatments) replicated 4 times with 4 nontreated controls for each drill width spacing. Each trial consisted of a whole plot factor of 4 drill row width spacings: 5, 7.5, 10, and 15 in. The subplot factor consisted of 4 cultivars: medium-grain inbred (CLM04), long-grain inbred (CLL16), long-grain hybrid (RT 7301), and FullPage long-grain hybrid (RT 7521 FP). Results indicated no interaction of drill row width spacing and rice cultivar for any response variables. A decrease in barnyardgrass density was observed for the 7.5-in. spacing compared to the 15-in. spacing across site-years for the 5- to 6-leaf (preflood) and preharvest rice stages. A 43% decrease in barnyardgrass density was observed for the hybrid cultivars compared to the inbred at the preharvest timing. Based on small unmanned aerial system (sUAS) imagery at panicle differentiation, there was a 20 percentage point decrease in canopy coverage from the 7.5 in. drill row width to the 15 in. width. This research provides insights on alternative weed management efforts through more precise drill row width spacing and cultivar selection in an Arkansas flooded rice system. [ABSTRACT FROM AUTHOR]

Postemergence management of barnyardgrass [Echinochloa crus-galli (L.) P. Beauv] with evolution of resistance to acetyl-CoA carboxylase (ACCase) inhibitors is a challenging task. In a previous study, we confirmed several barnyardgrass accessions resistant metabolically to both the ACCase inhibitor cyhalofop-butyl (CyB; Clincher) and the synthetic auxin herbicide florpyrauxifen-benzyl (Loyant). The current study was performed to investigate effects of malathion (cytochrome P450 inhibitor) and/or 4-chloro-7-nitrobenzofurazan (NBD-Cl; glutathione S-transferase inhibitor) on metabolism of CyB in the resistant barnyardgrass accessions. Both malathion and NBD-Cl were not effective in restoring sensitivity of resistant barnyardgrass accessions to CyB (0.3 lb ai/ac). Rather, treatment with malathion followed by (fb) CyB antagonized the CyB's efficacy. Absorption of CyB in both CyB-susceptible (S) and resistant (R) barnyardgrass accessions was not influenced by malathion pretreatment. The consumption of CyB in S and R accessions decreased 1.5- to 10.5 times by pretreatment of malathion. However, production of cyhalofop-acid, the active herbicide form, was similar between treatments with CyB alone (1.8% to 17.3%) and treatments with malathion fb CyB (1.0% to 19.3%). Conclusively, malathion can antagonize CyB in barnyardgrass by contributing to reduced metabolism of CyB but not to its conversion to cyhalofop-acid. [ABSTRACT FROM AUTHOR]

Resistance to quizalofop-p-ethyl is the newest herbicide tolerance technology in rice fields. This technology provides resistance to the herbicides Provisia® and Highcard™ and adds a new mode of action for weedy rice control to the rice weed control portfolio. However, using additional chemistries is essential to ensure the prolonged viability of this technology and avoid weed resistance. Therefore, this study evaluated how benzobicyclon (Rogue®) fits into a Max-Ace® rice system where Highcard is used for weedy rice (Oryza spp.) and barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] control. The experiment was conducted in 2022 in Stuttgart, Arkansas, and organized in a two-factor randomized complete block with a split-plot setup. The whole-plot factor was with or without benzobicyclon postflood (POSTF), and the sub-plot factor was herbicide programs: 1) no herbicide, 2) quizalofop sprayed at early postemergence (EP) and preflood (PREF), 3) quizalofop sprayed at EP and POSTF, 4) quizalofop sprayed at PREF, and 5) quizalofop sprayed at POSTF, respectively. Weedy rice and barnyardgrass control was visually rated 4 weeks after POSTF treatments. Rough rice yields were obtained at the end of the season. For both weeds evaluated, the lowest control levels were obtained when quizalofop was only sprayed POSTF without benzobicyclon. Barnyardgrass and weedy rice control were above 95% whenever repeated herbicide applications of quizalofop were present, independently of benzobicyclon. The lowest yield was obtained in the treatment with a single application of quizalofop POSTF. The highest yields were obtained when treatments included benzobicyclon POSTF, or when quizalofop was sprayed twice in the season without benzobicyclon. The alliance of Max-Ace rice systems with an alternative herbicide like benzobicyclon is a potent weed control option to reduce the development of herbicide resistance throughout the years. [ABSTRACT FROM AUTHOR]

EnlistTM corn is a newly commercialized hybrid allowing the use of 2,4-D and quizalofop-methyl herbicides. Knowledge of Enlist corn tolerance to these labeled herbicides as well as other herbicides within the same mode of action (MOA) is not well established. Four site-year field experiments were conducted at Fayetteville (2021 and 2022) and Tillar (2020 and 2021) sites, in Arkansas, to evaluate Enlist corn response to postemergence applications of herbicides from two MOAs, synthetic auxin or acetyl-CoA carboxylase (ACCase)-inhibitors, that are common in Midsouthern crop production systems. A non-Enlist corn hybrid was used along with the Enlist corn for each herbicide treatment for comparison. Enlist corn showed injury to applications of florpyrauxifen-benzyl (>10%), fluazifop-P-butyl and quizalofop-P-ethyl (>5%), and clethodim and sethoxydim (>75%) 1 week 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 on non-Enlist corn with ACCase-inhibiting herbicides 1 or 2 WAA was >80%, resulting in a proportionate yield reduction. Florpyrauxifen-benzyl caused more initial injury in non-Enlist corn; however, yield reduction in non-Enlist corn was occasionally less than in Enlist corn, with both hybrids experiencing >75% yield reduction. In summary, Enlist corn may occasionally show transient injury even to labeled herbicides, and injury from florpyrauxifen-benzyl may result in serious yield loss. [ABSTRACT FROM AUTHOR]

Drought events are predicted to increase in the future. Evaluating the response of herbicide-resistant and -susceptible weed ecotypes to progressive drought can provide insights into whether a resistance trait affects the fitness of resistant weed populations. Two experiments were conducted in a greenhouse between January and May 2021 to evaluate drought tolerance differences between Palmer amaranth (Amaranthus palmeri S. Wats.) accessions resistant to S-metolachlor (Dual Magnum®) or glyphosate (Roundup PowerMax™ II) and their susceptible counterparts. The accessions used were: S-metolachlor-resistant (17TUN-A), a susceptible standard (09CRW-A), and glyphosate-resistant and glyphosate-susceptible plants from accession 16CRW-D. The daily transpiration of each plant was measured. The daily transpiration rate was converted to normalized transpiration ratio (NTR) using a double-normalization procedure. The daily soil water content was expressed as a fraction of transpirable soil water (FTSW). The threshold FTSW (FTSWcr), after which NTR decreases linearly, was estimated using two-segment linear regression analysis. A greater FTSWcr means early stomatal closure with respect to the initiation of water deficit. The data showed differences between S-metolachlor-resistant and -susceptible accessions (P = 0.05). The FTSW remaining in the soil at the breakpoint for the S-metolachlor-susceptible accession (09CRW-A) was 0.17 ± 0.007. The FTSW remaining in the soil at the breakpoint for the S-metolachlor-resistant accession (17TUN-A) was 0.23 ± 0.004. The FTSW remaining in the soil at the breakpoint for the glyphosate-resistant and glyphosate-susceptible plants (16CRW-D) were 0.25 ± 0.007 and 0.25 ± 0.008, respectively. Although the mechanism endowing resistance to S-metolachlor might have contributed to increased drought tolerance, follow-up experiments are needed to verify this finding. Increased EPSPS copy number did not improve drought tolerance of Palmer amaranth. As droughts are predicted to increase in frequency and severity, these results suggest that S-metolachlor-resistant and glyphosate-resistant Palmer amaranth populations will not be at a competitive disadvantage compared to susceptible genotypes. Alternative and diverse management strategies will be required for effective Palmer amaranth control regardless of herbicide resistance status. [ABSTRACT FROM AUTHOR]

Herbicide resistance has become increasingly problematic in production agriculture, creating a great demand for alternative control options. Field studies were conducted at the University of Arkansas System Division of Agriculture's Jackson County Extension Center near Newport, Ark. and the Rohwer Research Station near Rohwer, Ark. to evaluate postemergence (POST) herbicide tank-mixtures in an Enlist® E3 soybean [Glycine max (L.) Merr.] system. Treatments consisted of Enlist One® (2,4-D choline) alone and in combination with other products, including Roundup PowerMax® II (glyphosate), Moccasin® (S-metolachlor), Liberty® (glufosinate), and Reflex® (fomesafen). Visual estimations of weed control and soybean crop injury were collected 14 and 21 days after application (DAA) of the initial POST treatment, which was made to 4-to 6-in.ch weeds. At the Jackson County location, soybean was drilled in 7.5-in. row widths, and at the Rohwer location, soybean was planted in 38-in. row widths. Visual control of Palmer amaranth (Amaranthus palmeri S. Wats.) was 100% at Jackson County across all rating timings; however, there was more variability between treatments at the Rohwer location. These data demonstrate the capability of reduced row spacing to aid in successful weed management efforts. Results from the Rohwer location highlight the importance of combining a non-selective herbicide such as Roundup PowerMax II or Liberty with Enlist One to provide excellent control (= 90%) of barnyardgrass (Echinochloa crus-galli P. Beauv.), as well as adding an overlapping residual herbicide to the tank-mixture to provide weed control throughout the season. [ABSTRACT FROM AUTHOR]

A field experiment was conducted in 2021 to evaluate the preemergence activity of metribuzin (group 5) and pyroxasulfone (group 15) herbicide combinations in the control of several weed species and to determine their effectiveness as preemergence options in soybean [Glycine max (L.) Merr.] weed management systems. All treatments provided nearly ideal control of Palmer amaranth [Amaranthus palmeri (S.) Wats.] (99%), pitted morningglory [Ipomoea lacunosa (L.)] (better than 95%), and prickly sida [Sida spinosa (L.)] (better than 97%) by 35 days after preemergence application (DA PRE). No significant impact of preemergence treatments was observed on stand loss. Overall, preemergence treatments resulted in less than 6% chlorosis and necrosis by 35 DA PRE. Additionally, only treatments with Glory® at 1.25 lb/ac (metribuzin) or 5.75 fl oz/ac of Zidua® (pyroxasulfone) plus Glory at 1.25 lb/ac resulted in 7% and 5% of crop stunting, respectively, by 35 DA PRE. In contrast, other treatments resulted in less than 1% visible stunting. Therefore, all herbicide treatments tested resulted in desirable weed control and minimal impact on early crop development. Utilizing a combination of herbicide sites of action could minimize the expansion of herbicide resistance. Generally, preemergence treatments do not provide robust weed control persisting for the entire critical weed-free period of soybean (from emergence to V4). Therefore, timely postemergence applications should be recommended to reduce possible yield impacts. [ABSTRACT FROM AUTHOR]

Palmer amaranth [Amaranthus palmeri (S.) Wats.] is one of the most troublesome soybean weeds [Glycine max (L). Merr.]. Chemical control options are limited with the evolution of resistance to 9 herbicide sites of action (SOAs) in Palmer amaranth. In 2021, a greenhouse experiment was conducted at the University of Arkansas System Division of Agriculture's Milo J. Shult Agricultural Research and Extension Center in Fayetteville, Ark., to evaluate the response of Arkansas Palmer amaranth populations to commonly used row crop herbicides with differing SOAs. Two experimental runs were conducted as a completely randomized design with 3 spatial replications. Three difficult-to-control accessions (A2019, A2020, and B2020) along with 1 standard susceptible accession (SS2001) were treated with 10 different herbicide SOAs, including pendimethalin and S-metolachlor as a preemergence application and imazethapyr, 2,4-D, dicamba, atrazine, diuron, glyphosate, glufosinate, fomesafen, paraquat, mesotrione, and tembotrione as a postemergence application. All difficult-to-control accessions were observed to have at least 20 percentage points less mortality than a susceptible standard to 5 herbicide SOAs. Mortality of A2019 accession was at least 20 percentage points less than the susceptible standard to herbicides from 9 differing SOAs. Additionally, A2020 and B2020 showed reduced sensitivity to 5 herbicide SOAs. Furthermore, atrazine and paraquat provided >86% mortality and are still viable options for controlling challenging Palmer amaranth populations. [ABSTRACT FROM AUTHOR]

Palmer amaranth (Amaranthus palmeri S. Watson), commonly known as Palmer pigweed, is a highly invasive weed that affects row crop production throughout Arkansas. Palmer pigweed has evolved resistance to most herbicide chemistries, and thus new technologies are urgently needed to control existing populations and curb the further spread. Bioherbicides-weed control agents derived from living organisms-have the potential advantages of being highly effective, specific, and environmentally friendly. However, to date, bioherbicides targeting Palmer pigweed have not been developed. This project's overarching goal is to utilize Palmer pigweed's fungal pathogens to create novel bioherbicides. In previous work, fungal pathogens of Palmer pigweed were isolated and cataloged from symptomatic plants collected throughout Arkansas. In this report, we utilized a greenhouse screening assay to identify highly virulent pathogens of Palmer pigweed. In addition, in a complementary approach, the most virulent pathogens identified in the greenhouse assay were evaluated for the production of phytotoxins (secondary metabolites produced by fungi that are toxic to Palmer pigweed). This approach identified 2 previously undescribed fungal isolates (AF22 and AF24) that are virulent on Palmer pigweed plants and produce 1 or more phytotoxins that induce wilting, charring, necrosis, and plant death. These 2 isolates have the potential to be utilized as biological control products, and the phytotoxin(s) produced by these strains could be developed into chemical bioherbicide products. [ABSTRACT FROM AUTHOR]

Widespread herbicide resistance is an issue in rice (Oryza sativa L.) due to the difficult control of the resistant weeds, making weed management challenging for farmers. Therefore, research of new modes of action to control herbicide-resistant weeds must also include evaluations of crop safety. Fluridone was tested for potential weed control in rice; however, little is known regarding the optimum application timing to reduce crop response. Therefore, this study aimed to evaluate the influence of fluridone application timing on rice tolerance. The experiment was conducted in 2022 at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center near Stuttgart, Ark. The experiment was organized as a randomized complete block with 10 application timings and 4 replications. The application timings were: 22 and 11 days preplant, preemergence (PRE), delayed-preemergence (DPRE), 1-leaf, 2-leaf, 3-leaf, 4-leaf, preflood, and immediately after flood establishment (post-flood). Nontreated control plots were included for comparison. Fluridone was applied at 0.15 lb/ac in all treatments. Visual rice injury and ground cover were collected 35 and 70 days after emergence (DAE), and rough rice yield was collected at maturity. At 35 DAE, PRE and DPRE treatments caused 13% and 11% visible injury, respectively. However, by 70 DAE, crop injury increased following the establishment of the flood, reaching 40% for both the PRE and DPRE treatments. Canopy loss occurred at 35 and 70 DAE for the PRE treatment compared to the nontreated control. Rice exhibited a high tolerance level to a post-flood fluridone application, comparable to the nontreated control. However, at the application timings PRE, DPRE, and 1-leaf, rough rice yield was lower than in plots where fluridone was not applied. Further research on rice tolerance to fluridone is needed over a wide range of environments as well as quantifying the weed control value of fluridone in drill-seeded rice culture. [ABSTRACT FROM AUTHOR]

Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is a highly problematic weed in flooded rice (Oryza sativa L.) that can result in significant yield losses when left unchecked. New methods of barnyardgrass control will be needed to preserve high yields in Arkansas rice production. S-metolachlor is a chloroacetamide herbicide that provides residual control of grasses and small-seeded broadleaf weeds. An experiment was conducted in Keiser, Ark. to evaluate the efficacy of S-metolachlor in a rice system in conjunction with a fenclorim seed treatment to mitigate the risk of crop injury. Three rates of S-metolachlor (0.5, 1.0, and 1.5 lb ai/ac) were applied delayed-preemergence to 'Diamond' rice that was treated with fenclorim at 0 or 2.5 lb of ai/1000 lb-seed. Visual injury to rice and visual control of barnyardgrass were rated in comparison with the nontreated control and were evaluated throughout the season. Rough rice yield was evaluated after harvest. While visual rice injury was higher on average in the first two weeks after treatment without fenclorim, by 28 days after treatment (DAT) the low rate of S-metolachlor combined with a fenclorim seed treatment caused less than 17% injury. S-metolachlor provided effective visual control of barnyardgrass at all three rates up to 28 DAT that exceeded 90% control. Overall, the presence of fenclorim reduced injury to rice at each rate of S-metolachlor, while not having an impact on weed control. At a rate of 0.5 lb ai/ac of S-metolachlor with a fenclorim seed treatment, rice yield was comparable with the nontreated control. However, increasing rates of metolachlor reduced yield. If S-metolachlor becomes labeled for use in rice, this will provide an alternative site of action for weed control without requiring a herbicide resistance trait. [ABSTRACT FROM AUTHOR]

Weedy rice in Arkansas is resistant to HRAC/WSSA group 1 and 2 herbicides that are commonly used for control. The ROXY® Rice Production System (RRPS) provides tolerance to herbicides containing oxyfluorfen. Oxyfluorfen is a Herbicide Resistance Action Committee/Weed Science Society of America (HRAC/WSSA) group 14 herbicide labeled for preemergence (PRE) and postemergence (POST) applications in many crops. Oxyfluorfen currently is not labeled for use in rice; however, the Roxy trait in the RRPS allows for applications of the herbicide. During the 2021 and 2022 growing seasons, two independent field trials were conducted at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center near Stuttgart, Ark. The first experiment was designed to determine if there was a rate response for weedy rice control associated with oxyfluorfen applied POST at the 2-leaf growth stage of weedy rice. The second experiment was designed to determine the optimal rate of oxyfluorfen to use PRE and POST in a sequential program when the maximum annual rate could not exceed 1.5 lb ai/ac. For the rate response experiment, oxyfluorfen (ALB2024) was POST-applied at 0.5, 0.75, 1, 1.25, or 1.5 lb ai/ac when the weedy rice reached the 2-leaf growth stage. In the sequential application experiment, mixtures of clomazone and oxyfluorfen (ALB2023) (0.3 plus 0.5, 0.75, or 1 lb ai/ac, respectively) were applied PRE, followed by a POST application of oxyfluorfen that resulted in the total amount of the herbicide applied being 1.5 lb ai/ac. Weedy rice control for all treatments ranged from 57 to 73% for the rate response experiment at 35 days after treatment. In the sequential application experiment, oxyfluorfen applied PRE resulted in 46 and 70% weedy rice control at the lowest (0.5 lb ai/ac) and highest (1 lb ai/ac) oxyfluorfen rates, respectively. At 14 days after the final treatment, 78 to 81% weedy rice control was observed for all treatments when oxyfluorfen was applied sequentially. Oxyfluorfen could potentially serve to suppress weedy rice in a RRPS; however, oxyfluorfen alone will not be able to achieve complete control. [ABSTRACT FROM AUTHOR]

In recent years, johnsongrass (Sorghum halepense) escapes and infestations have been a growing issue for cotton (Gossypium hirsutum) producers across the mid-South. This could be due to reliance on specific herbicides such as glyphosate and acetyl CoA carboxylase inhibitors. A greenhouse study was conducted in Fayetteville, Arkansas, in 2020 and 2021 to determine the extent of johnsongrass in Arkansas with resistance to aryloxyphenoxypropionate herbicides and glyphosate. Johnsongrass seeds were collected from 63 locations within six counties in eastern Arkansas. These accessions were then seeded in the greenhouse and treated with fluazifop at 0.9 lb ai/ac, quizalofop at 0.04 lb ai/ac, and glyphosate at 0.77 lb ae/ac. Quizalofop was the only herbicide that provided 100% mortality of all accessions. Some plants escaped fluazifop, but all accessions had greater than 90% mortality, except one accession from Crittenden County. Glyphosate resulted in variable levels of mortality, ranging from 10% to 100%. Overall, Arkansas johnsongrass accessions showed high levels of variability in control when treated with glyphosate, while fluazifop and quizalofop applications appeared effective on almost all of the accessions tested. [ABSTRACT FROM AUTHOR]

In United States' cropping systems, Palmer amaranth has become one of the most troublesome weeds, particularly in slow canopying crops such as cotton. A long-term field trial was initiated at the University of Arkansas System Division of Agriculture's Lon Mann Cotton Research and Extension Center, Marianna, Arkansas, to assess the impact of cultural and mechanical weed management strategies on Palmer amaranth over a three-year period. Non-chemical approaches such as tillage, cover cropping with cereal rye, and zero-tolerance were evaluated in combination with two standard weed control systems, one with dicamba used preemergence (PRE) and early postemergence (POST) compared to a program with no dicamba herbicide. The experiment was organized in a randomized complete block design with 16 treatments and four replications. Results showed that adopting a cover crop reduced weed emergence by 82%. The use of the zero-tolerance approach plus dicamba and non-dicamba herbicides showed comparative results, both causing a 63% reduction in Palmer amaranth emergence. A 37% reduction was observed in treatments that included tillage, but statistically, no difference was observed compared to treatments lacking tillage. The adoption of zero-tolerance with dicamba and non-dicamba herbicides plus the use of a cover crop (cereal rye) had a high impact on reducing the number of Palmer amaranth seedlings emerging throughout the trial. In the battle against herbicide resistance, the combination of multiple weed control practices (chemical, cultural, mechanical, and others) is essential to manage resistant weed populations and maintain sustainable cotton production. [ABSTRACT FROM AUTHOR]

Managing emerged weeds that have evolved resistance to herbicides is a challenging task. From dose-response experiments conducted previously, we selected barnyardgrass [Echinochloa crus-galli (L.) P. Beauv] biotypes susceptible (S) and resistant (R) to three aryloxyphenoxypropionate herbicides, namely cyhalofop-butyl (CyB; Clincher), fenoxaprop-ethyl (FeE; Ricestar HT), and quizalofop-ethyl (QuE; Provisia). For these barnyardgrass biotypes, absorption, translocation, and metabolism of CyB and QuE were evaluated to confirm the presence of a non-target-site resistance mechanism. Absorption, translocation, and total metabolism of tested herbicides were similar for S and R biotypes. Significant differences between S and R barnyardgrass were observed in the production of active acid forms of each herbicide (cyhalofop-acid and quizalofop-acid). Production of cyhalofop-acid was less in R barnyardgrass (3% to 8%) for 24 h after herbicide application than in the S barnyardgrass (8% to 16%). Meanwhile, the production of quizalofop-acid was less in R barnyardgrass (0% to 14%) throughout the study period than in the S barnyardgrass (3% to 22%). Overall results show that a non-target-site resistance mechanism altering the production of acid herbicide forms may contribute at least partly to the resistance of the tested barnyardgrass biotypes to CyB and QuE. [ABSTRACT FROM AUTHOR]

The control of barnyardgrass in Arkansas rice (Oryza sativa, L.) systems has plagued growers since the crop was first cultivated in the state. Now resistance to herbicides used in Arkansas production programs has complicated barnyardgrass control, and potential delays in herbicide applications due to weather events have made that control even more difficult. Two studies were conducted at the University of Arkansas at Pine Bluff Small Farm Outreach Center near Lonoke to evaluate potential salvage options for the control of barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] in Arkansas rice production. Ten herbicide treatments were applied at preflood and postflood in two separate trials. Results show that Ricestar HT alone did not control barnyardgrass in a last resort salvage situation. Ricestar HT mixed with several other herbicide options at full rates (Facet L, Regiment, Postscript, and Clincher) provided adequate control of barnyardgrass in this salvage situation when applied both preflood and postflood. Rough rice yields followed barnyardgrass control trends and demonstrated that several salvage treatment options saved yield potential. One aspect that needs to be carefully examined is whether the salvage treatment was economically feasible and whether saving yield potential was profitable to the grower. [ABSTRACT FROM AUTHOR]

The use of preemergence herbicide technology has become increasingly critical in the fight against weeds due to postemergence herbicide resistance. The objective of this study was to evaluate the use of metobromuron for efficacy and crop tolerance in soybean [Glycine max (L.) Merr.], when used alone and in combination with Tricor® (metribuzin) in comparison to Tricor, Linex® (linuron) and Trivence® (chlorimuron-ethyl, metribuzin, and flumioxazin) applied alone. Visual estimations of weed control for Palmer amaranth (Amaranthus palmeri S. Wats.) and soybean crop injury were collected 14, 28, and 35 days after the herbicide application. Weed control ratings ranged from 67.5% for metobromuron (2.11 pt/ac), as the least effective treatment, to 100% for Trivence at 28 days after application. No visual injury was observed on soybean from any treatment. These data demonstrate the importance of including preemergence herbicides in a successful weed management program as well as combining chemicals that utilize multiple, effective modes of action. [ABSTRACT FROM AUTHOR]

Johnsongrass [Sorghum halepense (L.) Pers.] escapes and infestations have been a growing issue for soybean [Glycine max (L.) Merr.] producers across the mid-south. Reliance on glyphosate and acetyl CoA carboxylase (ACCase) inhibitors for grass control could have increased resistant populations. A greenhouse study was conducted in Fayetteville, Ark., in 2020 and 2021 to determine the extent of johnsongrass in Arkansas with resistance to aryloxyphenoxypropionate herbicides and glyphosate. Johnsongrass seeds were collected from 63 locations within 6 counties in eastern Arkansas. These accessions were seeded in the greenhouse and treated with fluazifop at 0.9 lb ai/ac, quizalofop at 0.04 lb ai/ac, and glyphosate at 0.77 lb ae/ac. The only treatment resulting in 100% mortality of all accessions was quizalofop. Some escapes were observed to fluazifop, but all accessions, outside of one from Crittenden County, had greater than 90% control. Variable levels of mortality, ranging from 10% to 100%, were observed with glyphosate. Overall, Arkansas johnsongrass accessions showed high levels of variability in control when treated with glyphosate, while fluazifop and quizalofop applications appeared effective on the accessions tested. [ABSTRACT FROM AUTHOR]

Dicamba and glufosinate have been effective herbicides used for postemergence weed control in XtendFlex® technology. The occurrence of Palmer amaranth (Amaranthus palmeri S. Wats.) escapes in fields that rely on these tools demonstrate the importance of monitoring the emergence and spread of herbicide resistance. For that purpose, Palmer amaranth accessions were collected from fields in regions where auxins (dicamba or 2,4-D) and glufosinate are heavily relied upon for weed control. Collections occurred in the fall of 2018, 2019, and 2020 from fields located in Mississippi, Missouri, Nebraska, Illinois, Louisiana, Tennessee, and Arkansas. Every state did not sample for Palmer amaranth each year. Herbicide treatments equivalent to a 0.5X or 1X rate of dicamba at 0.25 and 0.5 lb ae/ac or glufosinate at 0.26 and 0.53 lb ai/ac were applied to greenhouse-grown plants at the 5- to 6-leaf stage. Some accessions could not be thoroughly evaluated due to limited seed availability or lack of seed viability. For all samples reported, at least 100 plants were assessed. Thus far, the screening has evaluated 193 and 206 accessions to dicamba and 210 and 215 accessions to glufosinate at a 0.5 and 1X rate of each herbicide, respectively. Evaluations of the accessions showed a high variability of plant responses to the herbicide treatments. Dicamba and glufosinate applied at a 0.5X rate resulted in less than 60% mortality to 22 and 31 accessions, respectively. Nevertheless, a full labeled (1X) rate of dicamba and glufosinate provide at least 80% mortality of 193 and 194 Palmer amaranth accessions, respectively. Future experiments will be conducted to determine the mechanism for reduced susceptibility to these herbicides as well as alternative herbicides that can be used to control these troublesome accessions. [ABSTRACT FROM AUTHOR]

The commercial launch of XtendFlex cotton technology allows producers to make postemergence applications of dicamba, glufosinate, and glyphosate. Weed size is a vital component of a postemergence chemical weed control program as it helps in managing the troublesome weeds at a critical time. Weed size can affect herbicide efficacy and interactions among herbicides. Field experiments were conducted at Keiser, Arkansas in 2019 and 2020, at an on-farm site near Crawfordsville, Arkansas in 2019, at the University of Arkansas System Division of Agriculture's Lon Mann Cotton Research Station, Marianna, Arkansas in 2020, and at the Milo J. Shult Agricultural Research and Extension Center, Fayetteville, Arkansas in 2020. The objective of the experiments was to determine the effects of weed size on sequential applications of dicamba, dicamba plus glyphosate, and glufosinate. All the experiments were implemented as three-factor, randomized complete block designs with factor-A being herbicide treatment (XtendiMax followed by (fb) Liberty, Liberty fb XtendiMax, XtendiMax + Roundup PowerMax fb Liberty, and Liberty fb XtendiMax + Roundup PowerMax), factor-B being the timing of sequential application (3-day and 14- day interval), and factor-C being weed size (3- to 4-in. and 14- to 16-in.). XtendiMax + Roundup PowerMax fb Liberty at 3-day and 14-day interval, and Liberty fb XtendiMax + Roundup PowerMax at a 14-day interval provided control above 90% on 3- to 4-in. tall Palmer amaranth at 28 days after the final application (DAFA). XtendiMax + Roundup PowerMax fb Liberty at 3-day and 14-day intervals were the most effective treatments and highly consistent in controlling the labeled and above-labeled sizes of Palmer amaranth. Sequential applications resulted in higher mortality at 28 days after the final application (DAFA) to 3- to 4-in. tall Palmer amaranth when compared with 14- to 16-in. tall plants. Optimizing multiple herbicide sites of action at critical periods of weed management in cotton helps to mitigate some of the risk for herbicide resistance. [ABSTRACT FROM AUTHOR]

Due to current label restrictions, producers cannot mix dicamba and glufosinate for postemergence applications on cotton. Because of this, producers must seek alternative application methods to fully utilize both of these herbicides for weed control in XtendFlex® crops. Six field trials were conducted in Fayetteville, Keiser, Crawfordsville, and Marianna, Arkansas to evaluate sequential dicamba and glufosinate applications. Four of these trials evaluated Palmer amaranth four to ten inches tall, and in the other two trials, it was less than four inches tall. Treatments included multiple timings of dicamba followed by (fb) glufosinate, glufosinate fb dicamba, dicamba fb dicamba, and glufosinate fb glufosinate. A mixture of dicamba and glufosinate, as well as dicamba and glufosinate alone, were also evaluated. Overall, dicamba fb glufosinate 14 days later had the highest Palmer amaranth control and was the only treatment to reach 100% control at the labeled weed size. Single applications of dicamba, glufosinate, and dicamba plus glufosinate did not result in Palmer amaranth control greater than 80% regardless of weed size. The implementation of sequential applications of dicamba and glufosinate, two effective sites of action for POST control of Palmer amaranth, will also help mitigate the evolution of herbicide resistance and help preserve available technologies. [ABSTRACT FROM AUTHOR]

Multiple herbicide-resistant weeds have resulted in a need to adopt a multifaceted approach to reduce selection pressure and mitigate the evolution of herbicide resistance. Previous studies have suggested that cover crops, deep tillage, zero-tolerance mechanical weed control, and the use of residual herbicides along with postemergence herbicides can all disrupt the emergence of weeds. A long-term study was initiated in Marianna, Arkansas, during the fall of 2018 to evaluate the influence of a one-time deep tillage, rye cover crop, dicamba- and non-dicamba-based herbicide programs, and zero-tolerance weed removal on Palmer amaranth (Amaranthus palmeri S. Wats.) emergence and density in the soil seedbank. This study was arranged as a split, split, split-plot with zero-tolerance being the whole-plot factor, deep tillage the sub-plot factor, cover crops the sub-sub-plot factor, and herbicide programs the sub-sub-sub-plot factor. Weed densities and emergence were measured in each plot at 21, 42, 63, and 72 days after planting, and inflorescence-producing weed counts were taken at harvest. Results from 2019 suggest that the use of deep tillage and zero-tolerance both reduced the amount of weed seed returned to the seedbank. Deep tillage reduced the number of inflorescence-producing weeds at the end of the season by 75%. Zero-tolerance reduced inflorescence-producing Palmer amaranth populations at the end of the season by 63%. Deep tillage also reduced cumulative, in-season Palmer amaranth emergence by 74%. This information will be beneficial in assisting crop producers on how to effectively control and reduce weed populations in an integrated manner. [ABSTRACT FROM AUTHOR]

Hemp sesbania (Sesbania herbacea) and northern jointvetch (Aeschynomene virginica) are among the top ten problematic rice (Oryza sativa) weeds in Arkansas. Several options are available for early-season control; but in the event of a failure or escape, there are few options for a post-flood salvage treatment that will provide adequate control. A field study was conducted in the summer of 2019 to evaluate halosulfuron (Permit), halosulfuron + thifensulfuron (Permit Plus), and halosulfuron + prosulfuron (Gambit) applied alone at multiple rates on hemp sesbania and northern jointvetch. Rates consisted of Permit at 0.33, 0.67, 1.00, and 1.33 oz/ac, Permit Plus at 0.38 and 0.75 oz/ac, and Gambit at 0.50, 1.00, 1.50, and 2.00 oz/ac. All treatments provided 100% control of both weed species at 3 weeks after treatment (WAT). At pre-harvest, all treatments still provided excellent control of greater than 94%. Permit and Gambit each applied at 1.00 oz/ac had the greatest numerical control (98%) of northern jointvetch at pre-harvest. The lowest labeled rates of the evaluated acetolactate synthase (ALS)-inhibiting herbicides would be advisable as they successfully controlled these weed species and would be more economical for the grower. For example, Permit at 0.33 oz/ac, Permit Plus at 0.38 oz/ac and Gambit at 0.50 oz/ac all controlled northern jointvetch and hemp sesbania over 95% at pre-harvest. Hemp sesbania and northern jointvetch were successfully controlled in a post-flood salvage situation using ALS-inhibiting herbicides alone. [ABSTRACT FROM AUTHOR]

Palmer amaranth (Amaranthus palmeri), a competitive pigweed native to desert regions of the southwestern United States and northern Mexico, has become one of the most significant weed pests affecting soybean, corn, and cotton producers in Arkansas. Both invasive and aggressive, its vast genetic variability has helped it evolve resistance to herbicides relatively quickly. The current tools available to control pigweed are limited and unsustainable; thus, an effective integrated weed management approach is required to achieve control. Native pigweed pathogens could provide effective biological control of these weeds, especially if the virulence of pathogens can be increased through non-transgenic means. Thus, the objectives of this research are to: (1) evaluate fungal pathogens of pigweed to identify highly aggressive isolates (potential bioherbicide strains) (2) increase the aggressiveness of selected isolates through molecular genetic (non-transgenic) approaches and (3) evaluate modified strains and select candidates to commercialize as bioherbicides of pigweed. [ABSTRACT FROM AUTHOR]

With the continued spread of herbicide-resistant Palmer amaranth throughout Arkansas, cotton weed control continues to be challenging. New technologies such as Enlist™ and XtendFlex™ cotton traits provide opportunity for the use of auxin-based herbicide programs, but some Palmer amaranth resistance to these herbicides has been recently discovered in Kansas. Loyant (florpyrauxifen-benzyl) is a new auxin herbicide labeled in rice and is effective in controlling a range of weed species including Palmer amaranth. Two trials were conducted in 2017 at the University of Arkansas System Division of Agriculture's Lonn Mann Cotton Research Station in Marianna and the Rohwer Research Station in Rohwer, Arkansas and in 2018 at Marianna and Tillar, Arkansas, to determine if Loyant could fit in a post-direct program for control of problem weeds in cotton at a layby timing and to determine the rate of Loyant necessary to achieve this control. Cotton injury observed from post-directed applications of Loyant was minimal through both years of research. In 2018, Loyant at 8 oz/ac plus Durango (glyphosate) at 32 oz/ac plus Diuron at 32 oz/ac provided 98% or greater control of Palmer amaranth and barnyard grass at both locations in addition to exceptional yields. [ABSTRACT FROM AUTHOR]

Weedy rice (Oryza sativa) is difficult to control in rice cropping systems due to its similarity to cultivated rice in combination with a high risk for evolution of herbicide resistance. With further developing herbicide resistance, the need for new sites of action (SOA) in rice production is essential. Gowan Company is actively pursuing registration of benzobicyclon (Rogue), a Group 27 4-hydroxyphenylpyruvate dioxygenase (HPPD) herbicide, as a post-flood option in rice. It will be the first HPPD herbicide commercially available in U.S. rice production. In 2018, a field experiment was conducted at the University of Arkansas System Division of Agriculture's Pine Tree Research Station near Colt, Arkansas. The experiment was implemented as a randomized complete block design with four replications. The objective of the experiment was to evaluate benzobicyclon- containing weedy rice control programs, most of which contain Provisia™ herbicide, in rice compared to a two-pass Provisia alone program. The herbicides used in the trial included Prowl H20 (pendimethalin), Bolero (thiobencarb), Warrant (acetochlor), pethoxamid, Provisia (quizalofop), and Rogue (benzobicyclon). The herbicides were applied in various combinations and timings, except all Rogue applications were post-flood. At two weeks after the post-flood application, >80% weedy rice control was observed for treatments sprayed at 4-leaf stage with Provisia followed by a post-flood application of Rogue. At four weeks after the post-flood application, the same treatment improved to >90% weedy rice control. No more than 9% injury was observed from treatments containing Provisia followed by Rogue, and yield from these treatments averaged 66 bu./ac higher than the treatment containing Provisia followed by Provisia. All other evaluated treatments severely injured rice or were noneffective. Therefore, the addition of benzobicyclon in Provisia rice systems could be a viable rice weed control option but additional years of research are needed to further validate this conclusion. [ABSTRACT FROM AUTHOR]

Palmer amaranth (pigweed) is a problematic and expensive management issue for Arkansas soybean producers. In addition to growing rapidly and prolifically producing seed, pigweed in Arkansas has developed herbicide resistance, which has contributed to increasing chemical management practices and associated costs over the last decade. Bioherbicides derived from fungal pathogens that naturally infect weeds are promising as alternative measures to control herbicide-resistant pigweed populations. Our overarching goal in this study is to create novel, highly aggressive bioherbicide products through unique molecular genetic approaches that specifically and effectively suppress Arkansas populations of pigweed. To date, pigweed-associated fungi and pigweed seed have been collected throughout Arkansas to identify candidate organisms for bioherbicide development. A total of 109 fungal isolates were collected from diseased pigweed. Of these, 86 isolates were collected from foliar material and 23 isolates were collected from seeds and diseased stalk material. Morphological and/or molecular identification revealed species of Colletotrichum, Cercospora, Fusarium, and Leptosphaeria in the collection, which provides excellent candidate organisms to enhance virulence via gene-editing approaches. The collection is currently being evaluated in pigweed pathogenicity assays to identify highly aggressive isolates for use as bioherbicides. [ABSTRACT FROM AUTHOR]

Weedy rice (Oryza sativa) is particularly difficult to control in mid-South rice cropping systems due to its highly competitive and resilient nature, similarity to cultivated rice, and resistance to herbicides. Hence, there is a need for new effective sites of action in mid-South rice production. Gowan Company is actively pursuing registration of benzobicyclon, a Group 27 herbicide, as a post-flood option in rice. It will be the first 4-hydroxyphenylpyruvate dioxygenase-inhibiting (HPPD) herbicide commercially available in mid-South rice production. In 2019, two field experiments were conducted at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center near Stuttgart, Arkansas, and the Pine Tree Research Station near Colt, Arkansas. The experiments were implemented as randomized complete block designs with four replications. The objective of the experiments was to evaluate benzobicyclon-containing weedy rice control programs, most of which contain Provisia™ herbicide, in mid-South rice compared to a sequential two-application Provisia alone program. The herbicides used in the experiments included Prowl H20 (pendimethalin), Bolero (thiobencarb), Warrant (acetochlor), Provisia (quizalofop), and Rogue (benzobicyclon). The herbicides were applied in various combinations and timings, except all benzobicyclon applications were made post-flood. At Stuttgart, four weeks after the post-flood application, >90% weedy rice control was observed for all treatments but was not significantly different. At four weeks after the post-flood application, =10% injury was observed from all treatments containing quizalofop followed by a post-flood application of benzobicyclon. At Pine Tree, four weeks after the post-flood application, >98% weedy rice control was observed for all programs containing quizalofop followed benzobicyclon. At four weeks after the post-flood application, no more than 4% injury was observed from all treatments containing quizalofop followed by benzobicyclon. Findings from these experiments show that the use of benzobicyclon in Provisia rice systems could be a viable weedy rice control option and may provide some protection against weedy rice evolving resistance to Provisia herbicide. [ABSTRACT FROM AUTHOR]

In 2019 the major project reported here involved the analysis of rice blast disease resistance conferred by the gene Pi40. We also performed genetic analysis on 10 major projects for rice breeding involving DNA marker-assisted selection (MAS) for the important traits of cooking quality, aroma, rice blast disease resistance, plant height, leaf texture, and the herbicide resistance systems Clearfield and Provisia at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC), near Stuttgart, Arkansas. Three smaller projects were conducted for the breeding programs as well. The Molecular Genetics lab screened 4663 test samples with up to 24 markers. The rice molecular analysis projects included parental materials, male sterile and restorer lines, selected F1 hybrid lines, and early and advanced generations of conventional breeding materials currently in development. In total, the lab generated 51,701 data points for 7 clients. The work was accomplished using 53 DNA template plates, 577 PCR plates, 118 runs on the ABI 3500xL to analyze simple sequence repeat (SSR) markers, and 218 PACE runs to analyze single nucleotide polymorphism (SNP) markers. In 2018 a line from the International Rice Research Institute (IRRI) which has the rice blast resistance gene Pi40 was crossed with some elite lines in the long-grain breeding program in order to introduce this powerful resistance gene into breeding materials with agronomic traits preferred by Arkansas farmers. The crosses resulted in 4 F2 populations grown in the field in 2019. A total of 880 plants was screened with 24 markers, with 14 of them linked to 6 blast resistance genes. Through this analysis, it was determined that the IRRI line had the genes Pi-b and Pi-ta in addition to the Pi40 gene. The Arkansas parents of two of the populations also had Pi-ta and Pi-kh. Analysis of the progeny revealed that approximately 25% of the plants had inherited the Pi40 gene. Molecular analysis was essential in determining the total rice blast disease resistance potential for the progeny so that selections could be made to promote further advancement in the program. [ABSTRACT FROM AUTHOR]

Mid-South growers continue to face limited post-emergence (POST) weed control options for Palmer amaranth (Amaranthus palmeri S. Wats) in cotton production. With few POST options available, there is a strong need to reduce selection for herbicide resistance by beginning weed-free with the intensive use of pre-emergence (PRE) herbicides. The addition of Brake (fluridone) as a PRE herbicide option in cotton has been shown to be effective on Palmer amaranth, and when used in combination with other PRE herbicides, may improve the spectrum of control and extend residual activity. To evaluate the efficacy of Brake on Palmer amaranth, an experiment was conducted near Marianna, Arkansas in 2018. All Brake-containing treatments demonstrated greater efficacy than the Cotoran (fluometuron) plus Caparol (prometryn) weed control standard, as well as provided extended residual control. [ABSTRACT FROM AUTHOR]

The latest USDA Cattle on Feed report revealed a record number of cattle in feedlots on March 1 since 1996. - Farm Futures USDA finalizes organic dairy rule USDA's National Organic Program will oversee the new Origin of Livestock Rule, which determines which animals can be considered organic and produce organic milk. - Farm Progress And just for fun... Favorite farm dog of 2022 It's that time of year again: Prairie Farmer is honoring the farm dogs that make our farms more like home - herding livestock, greeting visitors, riding shotgun and making our farm lives richer and fuller. [Extracted from the article]

New technology like RAP helps ranchers "help the land" in order to sustain wildlife, provide food and fiber, and support agricultural families long into the future. As soon as they see that their plant productivity is declining - and revenue following suit - they can take steps to address the limitations and boost productivity again. [Extracted from the article]

This article offers suggestions for dealing with drought. The role of keeping data on inventory and operations on the success of one's plan is explained. It advises on applying herbicide for better weed management. The importance of having an exact estimate of the nutritive value of hays is emphasized.