Explore the vast range of titles available.

Palmer amaranth (Amaranthus palmeri S. Watson) resistant to atrazine [6‐chloro‐N‐ethyl‐N’‐(1‐methylethyl)‐1,3,5‐triazine2,4‐diamine] and 4‐hydroxyphenylpyruvate dioxygenase (HPPD)‐inhibiting herbicides was confirmed in a seed corn (Zea mays L.) production field in Nebraska, in 2014. Neither atrazine nor HPPD inhibitors (mesotrione [2‐(4‐mesyl2‐nitrobenzoyl)‐3‐hydroxycylohex‐2‐enone], tembotrione 2‐[2‐chloro‐4‐(methylsulfonyl)‐3‐[(2,2,2‐trifluoroethoxy) methyl]benzoyl]‐1,3‐cyclohexanedione, or topramezone [3‐(4,5‐dihydro‐3‐isoxazolyl)‐2‐methyl‐4‐(methylsulfonyl)phenyl](5‐hydroxy‐1‐methyl‐1H‐pyrazol‐4‐yl)methanone) applied post‐emergence were able to control resistant Palmer amaranth even at greater than label rates. However, their tank mixtures even at lower than the label rate provided more than 90% control under greenhouse and field conditions. The objectives of this study were to investigate the effect of atrazine on mesotrione absorption and translocation when tank mixed or vice versa in atrazine‐ and HPPD inhibitor‐resistant Palmer amaranth from Nebraska. Tank mixing commercial formulation of atrazine at 560 g ha−1 increased 14C‐mesotrione absorption to 51% compared to 39% with 14C‐mesotrione alone. However, 14C‐atrazine absorption or translocation was not affected by mesotrione at 26 g ha−1 in the tank mixture. Similarly, mesotrione did not affect the metabolism of 14C‐atrazine in resistant or susceptible plants when tank mixed compared to 14C‐atrazine applied alone. Increased absorption of mesotrione when tank mixed with atrazine could be one of the reasons of atrazine and mesotrione synergism besides their biochemical interaction in the atrazine‐ and HPPD inhibitor‐resistant Palmer amaranth biotype from Nebraska. Core Ideas Atrazine applied in tank‐mixture increased mesotrione absorption. Mesotrione applied in tank mixture did not affect atrazine absorption and translocation. Atrazine metabolism was not affected by mesotrione applied in tank mixture.

Herbicides, such as tembotrione, that inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD) enzyme are used to control broad spectrum of weeds, primarily in corn, as this crop can metabolize these herbicides via cytochrome P450 activity. In 2018, a Palmer amaranth ( Amaranthus palmeri ) population, KCTR was found to be resistant to multiple herbicides including, tembotrione in Kansas (KS), USA. However, the mechanism of tembotrione resistance in KCTR is not known. The objective of this study was to characterize the level of tembotrione resistance and investigate the mechanism of resistance to this herbicide in KCTR using a known susceptible Palmer amaranth population (KSS). Tembotrione dose response experiments revealed that KCTR Palmer amaranth is 23 times more resistant to this herbicide, than KSS. No difference in absorption or translocation of [ 14 C] tembotrione between KSS and KCTR was found. However, the time required to metabolize 50% of tembotrione was shorter in KCTR than in KSS. More than 95% of tembotrione was metabolized at 6 hours after treatment (HAT) in the KCTR, compared to only 50% in KSS plants. Application of cytochrome P450-inhibitors (e.g., malathion or piperonyl butoxide), along with tembotrione reversed the resistance in KCTR. Furthermore, the KCTR plants showed 35-fold increase in constitutive expression of C YP81E8 gene compared to KSS. Nonetheless, the HPPD gene expression was not altered in KCTR Palmer amaranth. Our results suggest that enhanced metabolism of tembotrione possibly due to increased expression of C YP81E8 gene contribute to tembotrione resistance in KCTR. Metabolic resistance to herbicides is a challenge for weed management as such resistance predisposes weeds to evolve resistance to unknown herbicides even without selection.

Palmer amaranth (Amaranthus palmeri S. Watson) is not native to Africa. Based on the presence and persistence of A. palmeri populations, its invasive status in southern Africa is classified as “naturalized.” Globally, A. palmeri is one of the most troublesome weed species in several crops, including soybean [Glycine max (L.) Merr.], maize (Zea mays L.), and cotton (Gossypium hirsutum L.). Certain populations of A. palmeri in various countries were reported to be resistant to herbicides with different sites of action (SOAs). Two biotypes of A. palmeri in the United States reportedly each have resistance to herbicides representing five different SOAs, and between them a total of eight different SOAs are involved. Resistance mechanisms in these biotypes involve target-site and/or non–target site resistance. Here we characterize a specific A. palmeri population that was found in the Douglas district in South Africa and showed resistance to various herbicide SOAs. Initially, this A. palmeri population was discovered in a glyphosate-tolerant cotton field, where it survived glyphosate treatment. Subsequently, greenhouse experiments were conducted to characterize this A. palmeri population for potential resistance to herbicides of additional SOAs, and molecular analyses were conducted to reveal the mechanisms of herbicide resistance. Results indicated resistance to chlorimuron-ethyl and glyphosate in this population, while <90% control (decreased sensitivity) was observed at the label rate for mesotrione, atrazine, saflufenacil, and S-metolachlor. However, glufosinate, tembotrione, acifluorfen, dicamba, 2,4-D, metribuzin, acetochlor, isoxaflutole, diflufenican, and pyroxasulfone were effective at controlling this population. This profiling of herbicide sensitivity has allowed development of programs to control and potentially minimize the spread of this weed. In addition, molecular analysis of EPSPS revealed the role of higher copy number as a mechanism for glyphosate resistance in this population and a Ser-653-Asn target-site mutation likely conferring resistance to the acetolactate synthase–inhibitor chlorimuron-ethyl. No known target-site mutations were identified for the protoporphyrinogen oxidase–inhibitor group.

Certain plant species have the potential to establish themselves in agricultural fields, especially when they are already present nearby. Their spread can be influenced by improper management or intentional and unintentional introduction. Recently, cut-leaved gipsywort (Lycopus exaltatus L.) has been increasingly present in some row crops, where it was previously found only along field edges and irrigation channels, with no data about their presence in crops. Currently, no effective control methods for this rhizomatous species have been reported. To address this, 11 herbicides commonly used for weed management in major crops were evaluated in greenhouse studies. These included bentazon, dicamba, foramsulfuron, glyphosate, halauxifen-methyl, imazamox, mesotrione, nicosulfuron, tembotrione, thifensulfuron-methyl, and tribenuron-methyl. A dose-response study was conducted to identify the most effective option for cut-leaved gipsywort control using existing crop protection products. The study evaluated percentage reductions in dry biomass and canopy cover. The results suggest that bentazon, as the only nonsystemic herbicide, was least effective in controlling cut-leaved gipsywort with an effective dose (ED90) estimated at 1.5 × of the recommended labeled rate, or 2,205 g ai ha-1. Plants exposed to dicamba exhibited no regrowth at the field-use rate. Cut-leaved gipsywort may regrow when foramsulfuron, mesotrione, nicosulfuron, and tembotrione are applied at the recommended field-use rates. Halauxifen-methyl and imazamox were most effective, with estimated ED90 values of 0.21 × (0.85 g ai ha-1) and 0.4 × (16.14 g ai ha-1), respectively, which are lower than the recommended labeled rates. Although reduced rates are not recommended because good herbicide stewardship practices should aim to prevent the development of herbicide resistance, with both halauxifen-methyl and imazamox, cut-leaved gipsywort exhibited no regrowth when one-half of the recommended labeled rates were applied. Nomenclature: Bentazon; dicamba; foramsulfuron; glyphosate; halauxifen-methyl; imazamox; mesotrione; nicosulfuron; tembotrione; thifensulfuron-methyl; tribenuron-methyl; cut-leaved gipsywort; Lycopus exaltatus L. LYAEX

Mixing ammonium sulfate (AMS) can increase dicamba volatility. Therefore, AMS cannot be used with dicamba products in dicamba-resistant soybean. However, most dicamba products applied in corn are labeled to mix with AMS. The objectives of this study were to evaluate broadleaf weed control with dicamba (DiFlexx®) and dicamba/tembotrione (DiFlexx® DUO) applied alone or with AMS or AMS substitute and their effect on broadleaf weed density and biomass. Field experiments were conducted in Illinois, Missouri, and Nebraska in 2018 and 2019. In Illinois and Nebraska, mixing AMS + crop oil concentrate (COC) with dicamba applied at 1,120 g ae ha–1 increased the control of Palmer amaranth and waterhemp (Amaranthus species) from 78% to 92% and velvetleaf from 73% to 96% compared with dicamba applied alone 14 d after application (DAA); however, Missouri data showed no difference. Mixing AMS + COC with dicamba/tembotrione at 597 and 746 g ai ha–1 did not improve broadleaf weed control 14 DAA at any site compared with dicamba/tembotrione applied alone. Control of Amaranthus species was increased from 82% with dicamba applied at 840 g ae ha–1 to 96% when mixed with AMS + COC 28 DAA in Illinois; however, control was similar to dicamba applied at 1,120 g ae ha–1. Broadleaf weed control did not differ among dicamba or dicamba/tembotrione 28 and 56 DAA in Missouri and Nebraska. Broadleaf weed density decreased from 64 plants m–2 to 24 plants m–2 with dicamba at 1,120 g ae ha–1 with AMS + COC 14 DAA in Nebraska; however, no differences were observed in broadleaf weed density or biomass 56 DAA in any state. The results suggest that dicamba or dicamba/ tembotrione can be applied without AMS or AMS substitute, especially at higher rates, without losing broadleaf weed control efficacy. Nomenclature: Dicamba; dicamba/tembotrione; Palmer amaranth; Amaranthus palmeri S. Watson (AMAPA); velvetleaf; Abutilon theophrasti Medik. (ABUTH); waterhemp; Amaranthus tuberculatus (Moq.) J.D. Sauer (AMATU); corn; Zea mays L.; soybean; Glycine max (L.) Merr.

Postemergence grass weed control continues to be a major challenge in grain sorghum [ Sorghum bicolor (L.) Moench], primarily due to lack of herbicide options registered for use in this crop. The development of herbicide-resistant sorghum technology to facilitate broad-spectrum postemergence weed control can be an economical and viable solution. The 4-hydroxyphenylpyruvate dioxygenase-inhibitor herbicides (e.g., mesotrione or tembotrione) can control a broad spectrum of weeds including grasses, which, however, are not registered for postemergence application in sorghum due to crop injury. In this study, we identified two tembotrione-resistant sorghum genotypes (G-200, G-350) and one susceptible genotype (S-1) by screening 317 sorghum lines from a sorghum association panel (SAP). These tembotrione-resistant and tembotrione-susceptible genotypes were evaluated in a tembotrione dose–response [0, 5.75, 11.5, 23, 46, 92 (label recommended dose), 184, 368, and 736 g ai ha –1 ] assay. Compared with S-1, the genotypes G-200 and G-350 exhibited 10- and seven fold more resistance to tembotrione, respectively. To understand the inheritance of tembotrione-resistant trait, crosses were performed using S-1 and G-200 or G-350 to generate F 1 and F 2 progeny. The F 1 and F 2 progeny were assessed for their response to tembotrione treatment. Genetic analyses of the F 1 and F 2 progeny demonstrated that the tembotrione resistance in G-200 and G-350 is a partially dominant polygenic trait. Furthermore, cytochrome P450 (CYP)-inhibitor assay using malathion and piperonyl butoxide suggested possible CYP-mediated metabolism of tembotrione in G-200 and G-350. Genotype-by-sequencing based quantitative trait loci (QTL) mapping revealed QTLs associated with tembotrione resistance in G-200 and G-350 genotypes. Overall, the genotypes G-200 and G-350 confer a high level of metabolic resistance to tembotrione and controlled by a polygenic trait. There is an enormous potential to introgress the tembotrione resistance into breeding lines to develop agronomically desirable sorghum hybrids.

Weeds are the major biotic factor which reduces productivity of maize crop. Therefore, field trials were conducted during kharif seasons of 2015 and 2016, and rabi seasons of 2015–16 and 2016–17 with the hypothesis that combinations of tembotrione with different herbicides would provide effective weed control of complex weed flora with higher maize productivity and economic returns. Seventeen treatments comprising combinations of pre (atrazine, alachlor) and post-emergence herbicides (tembotrione, 2,4-D), weedy check and weed free were evaluated in randomized block design with three replications. The results showed that application of alachlor as pre-emergence followed by tembotrione resulted in > 90, 100 and > 80% control of grass, broad-leaf and sedges, respectively, in comparison to weedy check. The yield attributes and yield of maize in this treatment was similar to weed-free. Further, this treatment recorded 24–25% higher number of grains cob −1 , 35–40% higher grain weight cob −1 , and 17% higher 100-grain weight as compared to weedy check. This treatment had 3.43–3.54 Mg ha −1 higher grain yield (6.38 and 6.82 Mg ha −1 ) and 3.49–3.76 Mg ha −1 higher stover yield (8.38 and 9.07 Mg ha −1 ) than weedy check treatment during 2015 and 2016, respectively. The highest return over variable cost (652 and 735 USD ha −1 ) and benefit:cost ratio (1.94 and 2.11) was recorded in this treatment which was 87–97% and 45–47% higher than weedy check during 2015 and 2016, respectively. The different herbicide applied in kharif maize had no visible phyto-toxicity on maize as well as succeeding wheat crop in rabi season. This study intended to demonstrate better weed management practices in kharif maize with higher productivity and wider adoption of maize-wheat system in western IGP of India.

The present study was undertaken to investigate the dissipation behavior of tembotrione in soil and its effect on the biochemical constituents of maize leaves and grain. The average recovery of tembotrione from soil, maize grain, and stover was in the range of 84.0 to 86.0%, 79.3 to 83.0%, and 81.0 to 84.4%, respectively, with RSD less than 10%. Half-life (DT 50 ) of tembotrione ranged from 9 to 14 days at an application rate of 60 to 240 g ha −1 . Terminal residues in soil, maize grain, and stover were below detectable levels (≤ 0.025 µg g −1 ) at studied application rates. The chemical attributes, i.e., total chlorophyll, total carotenoids, and carbohydrate content, of rice leaves were observed at monthly intervals (zero (2 h), 30, 60 days after the herbicide application) and at harvest for biochemical analysis and grain samples at maturity of the crop for carbohydrate content. The results revealed that total chlorophyll, total carotenoids, and carbohydrate content in maize leaves increased significantly with applied tembotrione treatments, and the maximum increase was noticed in treatment 120 g ha −1 . A significant increase in total carbohydrate content in maize grain over the control was noticed in all the herbicide-applied treatments. It can be inferred that the application of tembotrione is safe in the production of food with better quality and food safety.

Pink purslane is often ranked as one of the most troublesome weeds in vegetable production systems in Georgia. Pink purslane encroachment along field edges and in-field of agronomic crops has recently increased. Postemergence herbicides are an effective component of agronomic crop weed management. However, little research has addressed pink purslane control in agronomic crops. Therefore, greenhouse and field studies were conducted from 2022 to 2023 in Tifton, Georgia, to evaluate the response of pink purslane to postemergence herbicides commonly used in agronomic crops. Greenhouse screening provided preliminary evidence whereby 13 of the 21 postemergence herbicides evaluated provided ≥80% aboveground biomass reductions. These 13 herbicides were then used for field studies. Results from the field studies, pooled across two locations, indicated that only three of the 13 herbicides provided aboveground biomass reductions of ≥70% compared to the nontreated control. Those herbicides included atrazine at 1,682 g ai ha–1, glufosinate at 656 g ai ha–1, and lactofen at 219 g ai ha–1 with 79%, 70%, and 83% biomass reduction, respectively (P < 0.05). This research suggests that many of the postemergence herbicides used on agronomic crops will not effectively control pink purslane. Thus, when trying to manage pink purslane with postemergence herbicides in agronomic crops, growers should plant crops or cultivars that are tolerant of either atrazine, glufosinate, lactofen, or a combination of these. Nomenclature: Acifluorfen; atrazine; bentazon; carfentrazone; chlorimuron; dicamba; diclosulam; diuron; fomesafen; glyphosate; glufosinate; imazapic; lactofen; mesotrione; paraquat; tembotrione; tolpyralate; topramezone; 2,4-D choline; 2,4-DB; pink purslane, Portulaca pilosa L. PORPI

The widespread adoption of multiple-herbicide-resistant corn and soybean often causes the problem of volunteers in corn–soybean rotation, which necessitates alternative herbicides for effective management. The objective of this research was to evaluate PRE and POST herbicides labeled in corn for control of dicamba/glufosinate/glyphosate-resistant volunteer soybean. Field experiments were conducted from 2021 to 2023 near Clay Center, NE. Two separate field experiments were conducted to evaluate 12 PRE and 14 POST herbicides to control volunteer soybean in Enlist® corn. Soybean resistant to dicamba/glufosinate/glyphosate was planted perpendicular to corn rows to mimic volunteer soybean. Among the PRE herbicides tested, acetochlor/clopyralid/flumetsulam (1,190; 1,050/106/34 g ai ha–1) and acetochlor/clopyralid/mesotrione (2,304; 1,961/133/210 g ai or ae ha–1) provided 97% and 99% control of volunteer soybean, respectively, in 2021 and 68% and 89% control, respectively, in 2023 at 42 d after PRE. Among POST herbicides tested, 2,4-D choline (1,064 g ae ha–1), acetochlor/clopyralid/ mesotrione (2,304; 1,961/133/210 g ai or ae ha–1), atrazine/bicyclopyrone/mesotrione/S-metolachlor (2,409; 700/42/168/1,499 g ai ha–1), clopyralid/flumetsulam (192; 146/46 g ai ha–1), nicosulfuron + atrazine (34 + 1,120 g ai ha–1), and thiencarbazone-methyl/tembotrione + atrazine (76; 12/63 + 896 g ai ha–1) provided ≥97% volunteer soybean control, ≥94% density reduction, and ≥97% biomass reduction 28 d after POST herbicide application. Corn yield did not differ from the weed-free control in these treatments. The results of this study suggest that PRE and POST herbicides are available for control of dicamba/glufosinate/glyphosate-resistant volunteer soybean in Enlist® corn and that careful selection of an herbicide is required based on the herbicide-resistant soybean planted in the previous year. Nomenclature: 2,4-D choline; acetochlor; clopyralid; flumetsulam; mesotrione; atrazine; bicyclopyrone; S-metolachlor; nicosulfuron; thiencarbazone-methyl; tembotrione; corn, Zea mays L.; soybean, Glycine max (L.) Merr.