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Geyer larkspur is a native perennial forb that is toxic to cattle. Herbicide control of Geyer larkspur is variable and depends on the growth stage of the plant when the herbicide is applied. The objectives of this study were to 1) evaluate aminopyralid, aminopyralid + florpyrauxifen-benzyl, aminopyralid + 2,4-D, aminopyralid + metsulfuron-methyl, metsulfuron-methyl, triclopyr, and triclopyr + 2,4-D for efficacy in controlling Geyer larkspur; 2) determine whether plant growth stage (vegetative or flowering) at the time of herbicide application influences herbicide effectiveness; and 3) determine whether herbicide treatment alters the norditerpenoid alkaloid content of Geyer larkspur. Plots were established in eastern Wyoming in 2021 and northern Colorado in 2022. Herbicide application at the different phenological stages did not affect Geyer larkspur density at the Wyoming site (P = 0.1065; data not shown). Geyer larkspur density at the Wyoming site was reduced by all herbicide treatments 1 yr after treatment (YAT) at the vegetative stage and by all herbicides except triclopyr 2 YAT (P = 0.0249). Geyer larkspur density at the flowering stage was reduced by all herbicides except metsulfuron-methyl, triclopyr, and triclopyr + 2,4-D at 1 YAT and by triclopyr and triclopyr + 2,4-D at 2 YAT. In contrast, there were no differences in Geyer larkspur density across treatments at the Colorado site (P = 0.9621). Precipitation was below average several months prior to herbicide application, which may have affected herbicide effectiveness. The metsulfuron-methyl treatment resulted in the highest total alkaloid concentrations of Geyer larkspur at the vegetative stage and the lowest concentrations at the flowering stage at the Wyoming site. Efforts to control Geyer larkspur in semiarid rangelands can be effectively accomplished by applying aminopyralid herbicides at either the vegetative or flowering growth stage provided environmental conditions prior to herbicide application are sufficient for plant growth and uptake of the herbicide. Nomenclature: Aminopyralid; florpyrauxifen-benzyl; metsulfuron-methyl; triclopyr; 2,4-D; Geyer larkspur; Delphinium geyeri Greene

Khakiweed is a perennial broadleaf weed that is difficult to control because of its multiple means of reproduction, vigorous growth, and deep taproot. Khakiweed reduces the performance of pasture, pecan, and turf areas by choking out desirable grass and legume species. Because information on the effectiveness of contact and residual herbicides for control in pecan and pasture areas is limited, greenhouse studies were conducted to determine the effect of application timing, mode of action, and rate on khakiweed control. Preemergence and postemergence herbicides were applied to mature khakiweed plants at 0.25X, 0.5X, 1X, or 2X the label recommended rate for general broadleaf control. Biomass was collected 3 wk after application. Plants regrew from roots in the greenhouse until a second biomass harvest was collected at 6 wk after treatment (WAT). Metsulfuron-methyl, indaziflam, or pendimethalin was applied preemergence to the soil surface. All rates of preemergence herbicides provided high-efficacy control of regrowth (>85%) compared to the nontreated control. The efficacies of postemergence-applied metsulfuron-methyl, metsulfuron-methyl + nicosulfuron, indaziflam, aminopyralid + florpyrauxifen-benzyl, 2,4-D amine, and 2,4-D amine + florpyrauxifen-benzyl were also examined. All postemergence herbicide treatments exhibited control compared to the nontreated plants at both sample timings (3 and 6 WAT) and increased with herbicide application rate. No herbicide provided high-efficacy control during the initial postspray period (0 to 3 WAT). During the regrowth period (3 to 6 WAT), metsulfuron-methyl alone and in combination gave >85% control of khakiweed biomass, indicating that the sulfonylurea herbicides used in this study are well suited to controlling khakiweed. Nomenclature: Aminopyralid; florpyrauxifen-benzyl; indaziflam; metsulfuron-methyl; nicosulfuron; pendimethalin; 2,4-D; khakiweed, Alternanthera pungens Kunth; pecan, Carya illinoinensis (Wangenh.) K. Koch

The conclusions of the European Food Safety Authority (EFSA) following the peer review of the initial risk assessments carried out by the competent authority of the rapporteur Member State Slovenia for the pesticide active substance metsulfuron‐methyl are reported. The context of the peer review was that required by Commission Regulation (EU) No 1141/2010 as amended by Commission Implementing Regulation (EU) No 380/2013. The conclusions were reached on the basis of the evaluation of the representative uses of metsulfuron‐methyl as a herbicide on spring and winter cereals. The reliable endpoints concluded as being appropriate for use in regulatory risk assessment, derived from the available studies and literature in the dossier peer reviewed, are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.

Knotroot foxtail has become more prevalent and problematic in pastures and hayfields in the southeastern United States. Gaps exist in our knowledge of which herbicide practices are best for managing this species in bermudagrass forage production. This study was conducted to determine the efficacy of various ways to control knotroot foxtail in bermudagrass with herbicide applications in autumn, postemergence (POST), with and without also applying a herbicide in preemergence (PRE), in spring. The study was a randomized complete block with a factorial arrangement of treatments and included a nontreated control for both fall and spring timings. Glyphosate at two rates (0.35 or 0.7 kg ae ha–1), nicosulfuron (0.07 kg ai ha–1) + metsulfuron (0.012 kg ai ha–1), and hexazinone (1.3 kg ai ha–1) were applied alone in the fall or followed by indaziflam (0.067 kg ai ha–1) or pendimethalin (4.46 kg ai ha–1) in the spring. Three harvests were conducted throughout the growing season to evaluate weed species (knotroot foxtail, large crabgrass, and horsenettle) and bermudagrass biomass as well as overall species composition. The combination of fall and spring treatments did not affect weed species or bermudagrass biomass. Therefore, treatment main effects were analyzed by fall or spring application timing. A spring application of either pendimethalin or indaziflam increased bermudagrass biomass compared with that of the nontreated control. However, neither PRE herbicide effectively reduced knotroot foxtail biomass compared with the nontreated control, although pendimethalin did reduce season-long knotroot foxtail composition. Spring PRE herbicides are an effective tool for forage producers, but further research is needed to identify effective herbicides and additional approaches for the control of knotroot foxtail. Nomenclature: Glyphosate; hexazinone; indaziflam; metsulfuron-methyl; nicosulfuron; pendimethalin; Carolina horsenettle; Solanum carolinense L. SOLCA; knotroot foxtail; Setaria parviflora (Poir.) Kerguélen] SETGE; large crabgrass; Digitaria sanguinalis (L.) Scop. DIGSA; bermudagrass; Cynodon dactylon (L.) Pers. CYNDA

Pimelea trichostachya Lindl. is a native Australian forb responsible for livestock poisoning and reducing the productivity and sustainability of grazing enterprises. This study was conducted as a pot trial under controlled conditions to investigate an effective chemical management strategy for P. trichostachya, a method that did not leave standing dead plant material, as such material can also be toxic to grazing cattle. Three herbicides, including one pre-emergence (tebuthiuron) and two post-emergence herbicides (2,4-D and metsulfuron-methyl), were tested in pot trials for their efficacy on P. trichostachya. Results showed that tebuthiuron applied as either a granular (10% active ingredient, a.i.) or pelleted (20% a.i.) form efficiently reduced the emergence of P. trichostachya seedlings. Although some seedlings emerged, they perished within 7 days post treatment, leaving no residual plant matter. Testing now needs to be undertaken under field conditions to validate the findings within vegetation communities where potential non-target impacts need to be accounted for as well. The post-emergence application of 2,4-D and metsulfuron-methyl demonstrated that the highest efficacy and reduced application rates were achieved by treating earlier growth stages (i.e., seedlings) of P. trichostachya plants. In addition, the amount of toxic dead plant material was minimized due to the faster degradation of these small plants. These findings offer practical, cost-effective solutions for sustaining grazing lands from P. trichostachya challenges.

Trichoderma is an antagonist fungus used in agriculture and forestry for the diseases control. The use of the herbicides metsulfuton methyl and glyphosate is a common practice for weed control that limits Trichoderma use. This study has evaluated the toxic effects ofthe herbicides metsulfuron methyl and glyphosate on four strains of fungi of the genus Trichoderma (GRB-HA1, GRB-HA2, GRB-HA8 and GRB-HA9). Poisoned media were prepared with high doses of 25 mL·L-1 of glyphosate + 0.2 g L-1 of metsulfuron methyl (D500) and low doses of 12.5 mL·L-1 of glyphosate + 0.2g L-1 of methyl metsulfuron (D250) to determine the effects on viability. The effects of the exposure time (30-90 min) on the germination of the conidia were determined using suspensions prepared with the mixtures D500 and D250. The results showed the differential sensitivity of the Trichoderma strains that affected the viability of the conidia and mycelial growth

The present paper discussed the comparison of the persistence and mobility of metsulfuron-methyl from a residue field trial experiment and simulation using a VARLEACH model. The residue field trial experiment was performed at Sungai Buloh Oil Palm Estate, Selangor. The plots were treated with metsulfuron-methyl at two treatment rates of 15 g a.i ha −1 (T1) and 30 g a.i ha −1 (T2). Soil samples were collected at 0, 1, 3, 7, 14, 21, 30, 60 and 90 days after treatment (DAT) and analysed subsequently by HPLC–UV. The results show that metsulfuron-methyl degraded rapidly in the soil with the half-life (t½) of 6.3 days in T1 and 7.9 days in T2. The simulation of VARLEACH model gave similar pattern of persistence and mobility of metsulfuron-methyl in the soil profile. However, total residues and the mobility of the metsulfuron-methyl were poorly simulated by the VARLEACH model due to consistent overestimation of the quantified residues. Results indicated that the metsulfuron-methyl lost more rapidly than the prediction values from VARLEACH model. In this case, simulation models which use transformation routines similar and which include additional degraded processes such as leaching, volatilisation, plant uptake or runoff could be considered. Albeit, overestimated values on the concentrations of metsulfuron-methyl are reported using VARLEACH model, the model still can be used as rapid and fast approach to predict the behaviour of pesticide at minimum cost.

Oilseed Brassica, an important edible oilseed crop of the world, is facing severe threat from the parasitic weed ‘Egyptian broomrape’ [ Phelipanche aegyptiaca (Pers.) Pomel] with yield penalty of 0-100%. The problem is more severe due to its physico-biochemical connection with the hosts, where, general weed control measures are not effective to control this parasitic weed. Since, there is no absolute measure to control Egyptian broomrape. The present study was aimed to identify and develop the most effective herbicide formulation and deliver the herbicide to the targeted underground parasite weed for effective and safe control in Indian mustard. Simple (single) and complex (combinational) smart herbicide formulations (NE, ME, SE, SC & ZC) were developed and evaluated under hot-spot conditions. Among all the smart formulations, metsulfuron methyl 5% SC @ 4 ml a.i./ha applied at pre-emergence stage was found most effective in controlling Egyptian broomrape with no phytotoxicity, and recorded higher seed yield of Indian mustard (48–74%) over weedy check plots. Residue analysis using LC-MS/MS revealed that metsulfuron methyl was not detected in soil as well as plant samples thus, it was environmentally safe also. This research successfully demonstrated that metsulfuron methyl-based smart formulations (5% SC) can safely and effectively control Egyptian broomrape in Indian mustard.

Pondweed is a rhizomatous perennial weed of aquatic habitats that recently adapted to rice ecosystems in northern Iran. Two field experiments were conducted at the Rice Research Institute of Iran to determine the impact of pondweed on rice yield and identify effective herbicides for pondweed control. The focus of the first study was to evaluate the herbicides commonly used in Iranian rice, including butachlor, pretilachlor, oxadiargyl, pendimethalin, thiobencarb, and bensulfuron-methyl. None of these herbicides effectively controlled pondweed, except bensulfuron, which reduced pondweed biomass by ≥95% and produced 26% higher rough rice grain yield than the nontreated plots. The second experiment evaluated the performance of acetolactate synthase–inhibiting herbicides on pondweed control, rough rice yield, and pondweed regrowth. Herbicide efficacy on pondweed varied from 36% to 100%. Five preemergence herbicides, bensulfuron at 45 g ai ha–1, flucetosulfuron at 30 g ai ha–1, triafamone plus ethoxysulfuron at 40 g ai ha–1, and metsulfuron-methyl at 15 g ai ha–1, provided ≥98% control of pondweed. Use of postemergence herbicides penoxsulam at 35 g ai ha–1, bispyribac-sodium at 30 g ai ha–1, and pyribenzoxim at 35 g ai ha–1 provided 36%, 89%, and 93% pondweed control, respectively. Rough rice yields ranged from 107% to 124% in herbicide-treated plots compared with the nontreated plots. Soil-applied herbicide treatments produced higher (≥119%) yield than the hand-weeded control or foliar-applied herbicides. Pondweed regrowth was affected by herbicides and was variable. Soil-applied residual herbicides metazosulfuron, flucetosulfuron, and metsulfuron provided complete control of pondweed and prevented regrowth. In contrast, pondweed regrowth in other soil- and foliar-applied herbicide treatments occurred, indicating their lesser translocation to underground vegetative rhizomes. This study shows that although most sulfonylurea herbicides can control pondweed effectively to achieve high rough rice yield, only a few soil-applied herbicides were able to prevent pondweed regrowth. Nomenclature: Bensulfuron-methyl; bispyribac-sodium; butachlor; flucetosulfuron; metazosulfuron; metsulfuron-methyl; oxadiargyl; pendimethalin; penoxsulam; pretilachlor; pyribenzoxim; thiobencarb; triafamone plus ethoxysulfuron; pondweed, Potamogeton nodosus Poir. ‘PTMNO’; rice, Oryza sativa L.

Radish (Raphanus sativus L.) and wild radish (R. raphanistrum L.) are troublesome agricultural weeds in several areas worldwide, with populations resistant to acetolactate synthase (ALS) inhibitor herbicide. Information on the mechanisms of resistance is important for management and developing novel solutions to control resistant populations. The objective of this work was to determine the ALS‐resistance mechanisms in radish and wild radish biotypes resistant to ALS‐inhibiting herbicides. Resistance levels were determined by dose‐response curve using several rates of metsulfuron‐methyl herbicide in susceptible (JUC1) and resistant (JUC2, CRA3) radish, and susceptible (CAF1) and resistant (CAF2, CAF3) wild radish biotypes. The mechanism was evaluated by the in vitro activity of the ALS enzyme with imazapic herbicide and ALS gene sequencing. All resistant biotypes were insensitive to metsulfuron‐methyl and imazapic herbicides. The rate of metsulfuron‐methyl to reduce 50% growth of the plants (GR50) were 17‐ to 60‐fold (JUC2, CRA3) and 9‐ to 21‐fold (CAF2 and CAF3) higher than the susceptible biotypes of radish and wild radish, respectively. One‐point mutation in the ALS gene, Trp‐574‐Leu, was found in all resistant radish biotypes, whereas a second point mutation, Ala‐360‐Ser, was found in CAF2, CAF3, and JUC2 resistant biotypes. Changes in kinetic parameters of the ALS enzyme were found in all resistant biotypes evaluated, causing reduction of the herbicide affinity in the target‐site of action. Trp‐574‐Leu amino acid substitution resulted in resistance to sulfonylurea, imidazolinone, and triazolopyrimidine groups, with the survival greater than 75% of the plants, depending on the herbicide applied at labeled rate.