Broadleaf Weed Control Research Articles

A smart sprayer for weed control in bermudagrass turf based on the herbicide weed control spectrum

Precision application of specific herbicides to susceptible weeds can significantly save herbicide. This is the first study evaluating the performances of precision sprayer for weed control in turf based on the herbicide weed control spectrum in field conditions. The results showed that EfficientNet-v2 and ResNet never fall below 0.992 for discriminating and detecting the grid cells encompassing weeds susceptible to ACCase-inhibiting and synthetic auxin herbicides. MCPA, a synthetic auxin herbicide, is used to evaluate the performance of the developed smart sprayer for precision control of broadleaf weeds in dormant bermudagrass turf. The developed smart sprayer prototype detected and sprayed every grid cell containing broadleaf weeds in field experiments. Compared to the broadcast application, precision spraying of MCPA provided the same level of control of broadleaf weeds. By 18 days after treatment (DAT), the nontreated control had 13 weeds no. m−2, while the plots that received broadcast and precision spraying had 0 and 1 broadleaf weed plant no. m−2, respectively. Precision herbicide application according to the herbicide weed control spectrum (HWCS) with the developed smart sprayer provided the same level of broadleaf weed control and could save more herbicides compared to an approach without discriminating weed species. Overall, these findings clearly indicated that the developed smart sprayer prototype could effectively detect, discriminate, and spray herbicides onto the grid cells containing target weeds based on the HWCS.

Legume re-establishment in northern temperate grasslands following application of aminocyclopyrachlor and aminopyralid

Herbicides with residual properties are often used for broadleaf weed control in pastures but can remove desirable legumes such as alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.). Field trials at five sites within central Alberta, Canada were used to assess legume population dynamics during recovery after spraying. Medicago sativa and T. repens populations were monitored for three years following application of aminopyralid (AMP) at 120 g a.i. ha−1, or aminocyclopyrachlor (AMCP) at 60 g a.i. ha−1, in combination with repeated mowing and legume over-seeding. Bioassays were performed twice a year (spring and fall) using M. sativa and T. repens seeded into soil sourced from each plot up until 26 months-after-spraying (MAS) and grown in a greenhouse. Medicago sativa and T. repens densities in the field remained below non-sprayed control levels throughout the study (26 MAS). In contrast, bioassay results indicated a shorter time than the field trial for legume recovery, with recovery occurring in soil from treated grassland as soon as 14 MAS. There were no differences between AMCP and AMP in the time required to facilitate legume establishment. Critically, legume establishment in the field depended on intermittent mowing, particularly for T. repens, which failed to persist in the absence of mowing at 22 MAS regardless of herbicide application. Medicago sativa had a high potential to establish from the natural seed bank, while T. repens depended on over-seeding. These findings indicate it may be possible to reintroduce legumes to temperate pastures as early as the second growing season after herbicide application, though field trials indicate legume population recovery will depend on seeding and secondary disturbances to reduce competition.

Impacts of Aminopyralid on Tomato Seedlings

Effective aminopyralid herbicides are commonly used to control broadleaf weeds in cereals or pastures, but their residues in straw or manure may damage cultivated crops and reduce the yield. In our experiments, the response of tomato plants to aminopyralid at doses of 0.6, 1.5, 3, 7.5, and 15 g/ha was evaluated, and extracts from straw treated with the herbicide Mustang Forte were tested. As the concentration of aminopyralid increased, seed germination was delayed by 1 to 3 days, compared to the control, and all the germinating seeds were deformed already at the lowest concentration of 0.6 g/ha. With the increased concentration of aminopyralid, injury to tomato plants also increased, and at the highest applied dose of 15 g/ha, 93.75% of the tomato plants were damaged. The critical level of concentration of aminopyralid in the soil was determined between 3 and 7.5 g/ha. Treatment with aminopyralid influences plant height in the indeterminate cultivar from an aminopyralid concentration of 3 g/ha and in the determinate cultivar from a concentration of 7.5 g/ha, but not as significantly. Thus, this experiment suggests that in the indeterminate cultivar, aminopyralid has a greater effect on height than in the determinate cultivar. This varietal sensitivity should be subjected to further study.

Influence of Glufosinate Rate, Ammonium Sulfate, and Weed Height on Annual Broadleaf Weed Control

Weed control efficacy with contact herbicides can depend on weed height at application. Four field experiments were conducted at sites with multiple weed species at different heights to determine the effect of weed height, glufosinate rate, and the addition of ammonium sulfate (AMS) on annual broadleaf weed control in soybean in southwestern Ontario, Canada, during 2021 and 2022. Glufosinate was applied at 300 or 500 g ai ha-1 without or with 6.50 L ha-1 of AMS to 5, 10, and 15 cm tall common lambsquarters (Chenopodium album L.), common ragweed (Ambrosia artemisiifolia L.), velvetleaf (Abutilon theophrasti Medik.), and redroot pigweed (Amaranthus retroflexus L.). Glufosinate provided excellent common ragweed control (> 98%) at both rates, without and with AMS, and at all three heights 4 weeks application (WAA). In contrast, glufosinate efficacy declined when applied to common lambsquarters, velvetleaf, and redroot pigweed > 5 cm in height. The addition of AMS to glufosinate improved common lambsquarters control. Increasing the rate of glufosinate to 500 g ai ha-1 and the addition of AMS improved control of velvetleaf and redroot pigweed. The results of this study demonstrate that the effect of glufosinate rate, AMS addition, and weed height at application timing is weed species-specific. In general, glufosinate (300 g ai ha-1) controlled common annual broadleaf weeds if weeds were < 5 cm in height; otherwise, glufosinate needed to be applied at 500 g ai ha-1 with AMS for control of annual broadleaf weeds, especially common lambsquarters, velvetleaf and redroot pigweed. 

Implications of atrazine concentrations in drinking water from Ijebu-North, Southwest Nigeria on the hypothalamic-pituitary-adrenal axis

There is an increasing overdependence and use of atrazine herbicide for the control of pre-and post-emergence broad leaf weeds on maize farms in rural agricultural communities in Nigeria. We carried out a survey of atrazine residue in 69 hand-dug wells (HDW), 40 boreholes (BH) and 4 streams from all the 6 communities (Awa, Mamu, Ijebu-Igbo, Ago-Iwoye, Oru and Ilaporu) in Ijebu North Local Government Area, Southwest Nigeria. The effect of the highest concentration of atrazine detected in the water from each of the communities on the hypothalamic-pituitary-adrenal (HPA) axis of albino rats was investigated. Varying concentrations of atrazine were detected in the HDW, BH and stream waters sampled. The highest concentration of atrazine recorded in the water from the communities ranged from 0.01 to 0.08 mg/L. Although there were no significant differences (p > 0.05) in serum levels of corticosterone, aldosterone and ROS of rats exposed to 0.01, 0.03 and 0.04 mg/L concentrations of atrazine compared to control, a significant increase (p < 0.05) was observed at 0.08 mg/L. Catalase activity increased significantly (p < 0.05) only at 0.03 and 0.04 mg/L of atrazine exposure. Butyrylcholinesterase activity, lipid peroxidation and serum ACTH of rats exposed to all the atrazine concentrations were not significantly different (p > 0.05) compared to control. Atrazine at environmentally relevant concentrations of 0.01, 0.03 and 0.04 mg/L detected in the water may not affect the HPA axis, attention should be given to 0.08 mg/L, which increases the serum corticosterone and aldosterone of the exposed rats.

Picolinafen exposure induces ROS accumulation and calcium depletion, leading to apoptosis in porcine embryonic trophectoderm and uterine luminal epithelial cells during the peri-implantation period

The global use of herbicides accounts for more than 48% of total pesticide usage. Picolinafen is a pyridine carboxylic acid herbicide that is predominantly used to control broadleaf weeds in wheat, barley, corn, and soybeans. Despite its widespread use in agriculture, its toxicity in mammals has rarely been studied. In this study, we first identified the cytotoxic effects of picolinafen on porcine trophectoderm (pTr) and luminal epithelial (pLE) cells, which are involved in the implantation process during early pregnancy. Picolinafen treatment significantly decreased the viability of pTr and pLE cells. Our results demonstrate that picolinafen increased the number of sub-G1 phase cells and early/late apoptosis. In addition, picolinafen disrupted mitochondrial function and resulted in the accumulation of intracellular ROS, leading to a reduction in calcium levels in both the mitochondria and cytoplasm of pTr and pLE cells. Moreover, picolinafen was found to significantly inhibit the migration of pTr. These responses were accompanied by the activation of the MAPK and PI3K signal transduction pathways by picolinafen. Our data suggest that the deleterious effects of picolinafen on the viability and migration of pTr and pLE cells might impair their implantation potential.

Graphene electrochemical transistors decorated by Ag nanoparticles exhibiting high sensitivity for the detection of paraquat over a wide concentration range.

Paraquat (PQ) is a nonselective contact herbicide used in agriculture for the control of broad leaf weeds, which would cause irreversible damage to human organs even at very low concentrations. Therefore, the trace residue detection of PQ in the environment is of vital importance. Here, a novel graphene electrochemical transistor (GECT) for PQ detection is reported for the first time. The key to the device design is the application of a layer of Ag nanoparticle (Ag NP) modified monolayer graphene as the channel layer. Due to the good electrochemical activity of Ag NPs for PQ detection, the device exhibits excellent sensitivity for PQ with the detection limit of 0.068 nM and a wide linear range from 0.1 nM to 5 mM. The GECT sensor also reveals good selectivity toward several common interferents and exhibits satisfactory recoveries for PQ detection when using Chinese cabbage as a simulant to deduce the real detection situation. The GECT sensor not only provides an efficient method for the detection of PQ residues, but also provides an effective grafting platform for the construction of novel high-sensitivity electrochemical sensors.

Cross species extrapolation of the disruption of thyroid hormone synthesis by oxyfluorfen using in vitro data, physiologically based pharmacokinetic (PBPK), and thyroid hormone kinetics models

The thyroid hormones play key roles in physiological processes such as regulation of the metabolic and cardiac systems as well as the development of the brain and surrounding sympathetic nervous system. Recent efforts to screen environmental chemicals for their ability to alter thyroid hormone synthesis, transport, metabolism and/or function have identified novel chemicals that target key processes in the thyroid pathway. One newly identified chemical, oxyfluorfen, is a diphenyl-ether herbicide used for control of annual broadleaf and grassy weeds in a variety of tree fruit, nut, vine, and field crops. Using in vitro high-throughput screening (HTS) assays, oxyfluorofen was identified to be a potent inhibitor of the thyroidal sodium-iodide symporter (NIS). To quantitatively assess this inhibition mechanism in vivo, we extrapolated in vitro NIS inhibition data to in vivo disruption of thyroid hormones synthesis in rats using physiologically based pharmacokinetic (PBPK) and thyroid hormone kinetics models. The overall computational model (chemical PBPK and THs kinetic sub-models) was calibrated against in vivo data for the levels of oxyfluorfen in thyroid tissue and serum and against serum levels of thyroid hormones triiodothyronine (T3) and thyroxine (T4) in rats. The rat thyroid model was then extrapolated to humans using human in vitro HTS data for NIS inhibition and the chemical specific hepatic clearance rate in humans. The overall species extrapolated PBPK-thyroid kinetics model can be used to predict dose–response (% drop in thyroid serum levels compared to homeostasis) relationships in humans. These relationships can be used to estimate points of departure for health risks related to a drop in serum levels of TH hormones based on HTS assays in vitro to in vivo extrapolation (IVIVE), toxicokinetics, and physiological principles.

Autumn Application of Synthetic Auxin Herbicide for Weed Control in Cereals in Poland and Germany

The biological efficacy of herbicides MCPA+tribenuron-methyl (code name: MT-565 SG) and diflufenican+chlorotoluron (Legato Pro 425 SC) was estimated in eighteen field experiments on winter cereals in Poland and Germany to control broadleaf weeds. Postemergence application of tribenuron-methyl in combination with MCPA, applied at the 3-leaf stage to 3 tillers detectable in autumn in winter cereals, resulted in the majority of weed species occurring in autumn being effectively eliminated with MCPA+tribenuron-methyl applied at 1.0 kg∙ha–1. It also provided an acceptable (82.4–94.1%) and comparable level of control to commonly occurring weeds Brassica napus, Capsella bursa-pastoris, Centaurea cyanus, Lamium purpureum, Tripleurospermum inodorum, Stellaria media, and Thlaspi arvense. A satisfactory level of control of 66.3 to 88.3% was confirmed for Veronica persica, Viola arvensis, and Galium aparine. According to these results, the formulation of tribenuron-methyl combined with MCPA can be recommended for application in winter cereals in the autumn as an alternative to commonly available herbicides.

Potentiometric MIP-Modified Screen-Printed Cell for Phenoxy Herbicides Detection.

In this study, a molecularly imprinted polymer (MIP)-based screen-printed cell is developed for detecting phenoxy herbicides using 2-methyl-4-chlorophenoxyacetic acid (MCPA) as the template. MCPA is a phenoxy herbicide widely used since 1945 to control broadleaf weeds via growth regulation, primarily in pasture and cereal crops. The potentiometric cell consists of a silver/silver chloride pseudo-reference electrode and a graphite working electrode coated with a MIP film. The polymeric layer is thermally formed after drop-coating of a pre-polymeric mixture composed of the reagents at the following molar ratio: 1 MCPA: 15 MAA (methacrylic acid): 7 EGDMA (ethylene glycol dimethacrylate). After template removal, the recognition cavities function as the ionophore of a classical ion selective electrode (ISE) membrane. The detected ion is the deprotonated MCPA specie, negatively charged, so the measurements were performed in phosphate buffer at pH 5.5. A linear decrease of the potential with MCPA concentration, ranging from 4 × 10-8 to 1 × 10-6 mol L-1, was obtained. The detection limit and the limit of quantification were, respectively, 10 nmol L-1 and 40 nmol L-1. A Nernstian slope of about -59 mV/dec was achieved. The method has precision and LOD required for MCPA determination in contaminated environmental samples.

Role of Antioxidant Enzymes and Glutathione S-Transferase in Bromoxynil Herbicide Stress Tolerance in Wheat Plants.

Background: Numerous pesticides and herbicides used in excess cause oxidative stress in plants. These chemicals protect plants from weeds and pests, but they also have very negative side effects, making them common abiotic stressors. One of the most significant nutritional crops in the world is the wheat plant. Conditions of herbicide stress have a negative impact on the plant’s phonological phases and metabolic pathways. Plants primarily make an effort to adjust to the environment and develop oxidative homeostasis, which supports stress tolerance. Methods: When controlling broadleaf weeds that emerge after cereal crop plants have been planted, bromoxynil is frequently used as a selective-contact herbicide. This study looked at the effects of the cyanobacteria Arthrospira platensis and Nostoc muscorum aqueous extracts, tryptophan, and bromoxynil (Bh) alone or in combination on wheat plant growth parameters. Both tryptophan and cyanobacterial extract were used as chemical and natural safeners against Bh application. The antioxidant activity and transcriptome studies using qRT-PCR were assayed after 24, 48, 72, 96 h, and 15 days from Bh application in the vegetation stage of wheat plants (55 days old). Results: In comparison with plants treated with Bh, wheat plants treated with cyanobacteria and tryptophan showed improvements in all growth parameters. Following application of Bh, wheat plants showed reduced glutathione content, as well as reduced antioxidant enzyme activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-s-transferase. The combination of different treatments and Bh caused alleviation of the harmful effect induced by Bh on the measured parameters. Additionally, the expression of glutathione synthase and glutathione peroxidase, in addition to those of three genes (Zeta, Tau, and Lambda) of the GST gene family, was significantly upregulated when using Bh alone or in combination with different treatments, particularly after 24 h of treatment. Conclusion: The current study suggests using cyanobacterial extracts, particularly the A. platensis extract, for the development of an antioxidant defense system against herbicide toxicity, which would improve the metabolic response of developed wheat plants.

Broadleaf weed control and white clover response to florpyrauxifen-benzyl + 2,4-D and common pasture herbicides

AbstractThe combination of florpyrauxifen-benzyl + 2,4-D is a new, pre-packaged herbicide mixture for use in pastures and hayfields in the United States. Unlike many other pasture herbicides, florpyrauxifen-benzyl + 2,4-D is reported to preserve white clover. However, limited research exists on the efficacy of florpyrauxifen-benzyl + 2,4-D on common weed species and on the level of tolerance of white clover to it. Field trials were conducted in Virginia in 2018 to 2020 to evaluate control of various broadleaf weeds with florpyrauxifen-benzyl + 2,4-D compared to other commonly used herbicides. Field and greenhouse studies were also carried out to assess white clover tolerance. Weed species evaluated included bulbous buttercup, Canada thistle, horsenettle, and broadleaf plantain. Florpyrauxifen-benzyl + 2,4-D provided 75% to 99% control of all weeds 90 d after application except for horsenettle (56%), while causing the least white clover injury of any herbicide treatment that was evaluated. Spring herbicide applications resulted in greater bulbous buttercup control compared to fall applications, but florpyrauxifen-benzyl + 2,4-D provided greater than 81% control from both application timings. There were no differences in aboveground biomass between white clover varieties; however, all herbicides reduced white clover biomass compared to a nontreated control. This research suggests that florpyrauxifen-benzyl + 2,4-D can improve overall forage quality by controlling broadleaf weeds in mixed grass-legume stands while preserving white clover.

Critical period of grass weed control in ALS-tolerant grain sorghum (Sorghum bicolor) is affected by planting date and environment

Field experiments were conducted at two locations in North Carolina (Clayton and Rocky Mount) to determine the influence of row spacing and planting date on the critical period of weed control (CPWC) of grass weeds in ALS-tolerant grain. Grain sorghum was planted in May and June 2019, with either a 38 or 91 cm row spacing using an ALS-tolerant sorghum variety. Treatments consisted of “weedy” or “weed-free” plots up to 2, 3, 5, and 7 weeks after crop planting (WAP) and two control treatments of weedy and weed-free all season. Selection of grass weed species was achieved by controlling broadleaf weeds with a premix of bromoxynil plus pyrasulfutole at a rate of 264 g a.i. ha-1.Grass weeds were controlled using nicosulfuron at a rate of 69 g of a.i. ha-1. The CPWC was significantly different across locations. Row spacing and planting date factors did not influence the CPWC at Clayton. Planting date was a significant factor for the CPWC at Rocky Mount, however row spacing did not have any effect on the CPWC. Results for the CPWC are presented in terms growing degree days (GDD) from the date of crop sowing. The CPWC for grass weeds in grain sorghum at Clayton was from 368 to 849 GDD. The CPWC at Rocky Mount for May-planted grain sorghum was from 405 to 876 GDD, while the CPWC for June-planted grain sorghum ranged from 228 to 1042 GDD. These results demonstrate that cultural and environmental factors may influence the beginning, duration and end of the CPWC.

Triangular Greenness Index to Evaluate the Effects of Dicamba in Soybean

Significant losses in agricultural production are due to abiotic stresses, such as herbicide phytotoxicity. Dicamba (diglycolamine salt) is a herbicide used for post-emergent control of broadleaf weeds. It has a possibility to vapor-spread into neighboring fields causing damage to other crops. However, not every stress can be easily identified. Therefore, remote sensing has the potential as a new tool in early injury detection. This study evaluated the effects of simulated dicamba drift on the occurrence of phytotoxicity in soybeans (Glycine max). Soybean was assessed in seven dicamba doses (0, 0.056, 0.56, 5.6, 11.2, 28, 112 g ha−1) for changes in plant injury (scale of notes), spectral aspects (triangular greenness index (TGI), and shoot dry mass. The plants were photographed using a digital camera positioned at 1.2 m above the planting media level. The results indicate a positive effect of low dicamba doses (0.56 and 0.056 g a.e. ha−1) on TGI canopy distinction and shoot dry mass. Soybean TGI canopy distinction and the injury scale estimated at 45 days after sowing, and the soybean shoot dry mass observed at 99 days after sowing, presented significant and moderate Pearson’s r coefficient of correlations (r = −0.609 and 0.625), indicating TGI as a valid and practical spectral index for plant dicamba-injured evaluations.

Integrated biomarker approach strongly explaining in vivo sub-lethal acute toxicity of butachlor on Labeo rohita

Butachlor herbicide belongs to the family of chloroacetanilide group, widely used for control of grass and broadleaf weeds in paddy fields however, its repeated application may result in aquatic pollution. Butachlor residue has been detected in aquatic environments, which may produce toxic effects on non-target organisms including fish. Keeping this in mind, the present study was designed to estimate the LC50 of butachlor (Shaktiman®), and to evaluate the sub-lethal toxicity at two concentrations (12.42 μg L−1 and 62.10 μg L−1) in Labeo rohita for a period of 24, 48, and 72 h. Fish exposed to butachlor reduced the counts of red blood cells (RBC), haemoglobin (HGB), hematocrit (HCT), and white blood cells (WBC). A significant (p < 0.05) increase in the antioxidant enzyme (superoxide dismutase-SOD, glutathione-s-transferase-GST), and hepatic enzyme (glutamate-oxaloacetate transaminase-GOT, glutamate-pyruvate transaminase-GPT) were noticed in butachlor exposed fish. Heat shock protein 70 (HSP70) and HSP90 in gill; cortisol, protein, albumin, globulin, and triglyceride in serum were increased upon exposure of butachlor. On the contrary, complement 3 (C3) and immunoglobulin (IgM) in serum was found to be decreased compared to control fish. The findings thus suggest that the fish upon exposure to butachlor disrupts the biomarkers which ultimately leads to growth retardation in fish.

The first report of chickpea (Cicer arietinum L.) tolerance to Paraquat in Australia

Chickpea growers in Australia have no post-emergent (POST) herbicides labeled for broadleaf weed control and they rely on pre-emergent herbicides for control of broadleaf weeds. The objective of this study was to evaluate chickpea tolerance to POST application of paraquat (0, 90, 180, 360, and 540 g ai ha-1) in a randomized complete block design. Paraquat (180 g ai ha-1) applied POST (up to 10 days after crop emergence) did not injure chickpeas and reduce plant height, and biomass when compared with nontreated control. When the crop just emerged, even the highest dose of paraquat (540 g ai ha-1) did not cause any injury or reduce chickpea biomass compared with nontreated control. Moderate toxicity to chickpea at paraquat 360 or 540 g ai ha-1 was observed when applied 20 days after crop emergence. This study suggests that paraquat POST has the potential to provide broad-spectrum weed control, including broadleaf weeds at an early stage of chickpea. However, the potential for crop injury to paraquat at higher doses, especially when applied at a late stage of the crop warrants further evaluation under field conditions. The study also suggests that tank mix applications of paraquat with residual herbicides may be useful for season-long weed control in chickpea and result in improved yield. The current study warrants further evaluation of the tank-mix application of paraquat with pre-emergent herbicides for season-long weed control under field conditions.

Effect of 2,4-D formulation on volatility under field conditions

AbstractAuxinic herbicides have been commonly used in production systems for broadleaf weed control for many years. One potential negative aspect to their use is their propensity to volatilize and move away from the treated area after application. This research examined three herbicide formulations and their relative amounts of vaporization following application under field conditions in Knoxville, TN, in 2017, 2018, and 2019. Herbicide treatments evaluated included 2,4-D choline, 2,4-D amine, and the diglycolamine (DGA) salt of dicamba. Ten field studies were conducted with major parameters including air sampler height (0.3 and 1.3 m) and applied surface condition (dry wheat stubble or green-plant vegetation). The relative volatility indicated by the study was that dicamba &gt; 2,4-D choline = 2,4-D amine. Detected herbicide concentrations were numerically higher at the 0.3-m sampling height and in the green-plant surface condition. These results confirm that dicamba is more volatile than 2,4-D and that there was no difference in vapor emissions between the amine and choline salts of 2,4-D under field conditions.

Fall-applied residual herbicides improve broadleaf weed management in ultra-early wheat (Triticum aestivum L.) production systems on the northern Great Plains

Ultra-early spring wheat ( Triticum aestivum L.) planting systems based on soil temperature on the northern Great Plains have lower overall variability in grain yield, and can increase grain yield relative to current calendar date-based spring wheat planting systems used in the region. However, ultra-early planting when soils are cold (2 °C), and resulting early crop emergence, precludes most foliar pre-seeding weed control options. Field trials were conducted at three sites in western Canada from 2017 to 2019 to evaluate the crop safety, broadleaf weed efficacy, and growing system stability resulting from the inclusion of fall applications of soil-applied residual herbicides prior to planting wheat ultra-early the following spring. Flumioxazin (protoporphyrinogen oxidase inhibitor; Weed Science Society of America (WSSA) group 14) and pyroxasulfone (very long chain fatty acid synthesis inhibitor; WSSA group 15) were applied alone and in combination at multiple rates in the late fall prior to ground freeze. The following spring, hexaploid spring wheat was planted ultra-early, based on a soil temperature trigger of 2 °C, and later, triggered by a soil temperature of 8 °C. When planting was completed ultra-early, grain yield was greater, and variability of grain yield was lower. Herbicide treatments increased broadleaf weed control, and in some environments further increased grain yield and reduced grain yield variability without resulting in phytotoxicity. The ability to safely incorporate fall-applied residual herbicides into ultra-early spring wheat planting systems provides an option for growers to adopt ultra-early planting without negatively impacting weed management on their farms.

Investment Returns for Preemergence Herbicide Use in No-till Pumpkin

Preemergence (PRE) herbicides are an important part of the overall weed management plan in no-till (NT) pumpkin (Cucurbita pepo) production. A field evaluation was conducted in an NT production system using PRE herbicides labeled for pumpkins to determine the benefits of specific herbicide combinations and the economic returns on investment associated with their use. The PRE herbicide treatments evaluated were 1) s-metolachlor (1360 g⋅ha–1 a.i.), 2) clomazone (350 g⋅ha–1 a.i.) and ethalfluralin premix (1120 g⋅ha–1 a.i.), 3) s-metolachlor + clomazone and ethalfluralin premix, 4) s-metolachlor + halosulfuron (35 g⋅ha–1 a.i.), 5) clomazone and ethalfluralin premix + halosulfuron, and 6) none. The primary weed species present were tall waterhemp (Amaranthus tuberculatus), redroot pigweed (Amaranthus retroflexus), giant foxtail (Setaria faberi), and large crabgrass (Digitaria sanguinalis). The best weed control option for full-season broadleaf and grass weed control was s-metolachlor + clomazone and ethalfluralin. This herbicide combination also provided the greatest economic return on investment, ranging from a 20% to 40% improvement (depending on the year) compared with the next closest PRE herbicide treatment. Those with the lowest returns on investment were s-metolachlor combined with halosulfuron, and clomazone and ethalfluralin combined with halosulfuron. Besides providing the highest returns on investment, the PRE application of s-metolachlor with clomazone and ethalfluralin also produced the largest pumpkin fruit for the weed species present. Although growers often look for ways to reduce input costs in NT pumpkin production systems, the proper selection of PRE herbicides that considers the weed species present is clearly an important investment that improves pumpkin yields and revenues.

Doses and Timing of 2, 4-D Application for Broadleaf Weed Control, Botanical Compositions, Productivity, and Nutritive Value of Natural Pasture

2,4-Dichlorophenoxyacetic acid (2,4-D) is among the most common and inexpensive herbicides used to control broadleaf weeds in natural pasture. However, different studies have pointed out the risk of forage injury. Consequently, no research data on the productivity and nutritive value of natural pasture in response to different rates and times of 2,4-D application exists in Ethiopia. Therefore, this study was conducted to investigate natural pasture yield and nutritive response to 2,4-D application at different rates (1, 1.5, and 2 L·ha−1) and time (mid-July, early, and mid-August) with control. The experiment was designed as a factorial randomized complete block design with three replicates for two years. Grasses and legume proportions in the pasture were significantly influenced by the rate and time ( P &lt; 0.05 ) of 2, 4-D application and their interaction ( P &lt; 0.001 ). Interaction of rate and time of 2, 4-D application had a significant ( P &lt; 0.05 ) influence on dry matter yield of legumes and non-significant ( P &gt; 0.05 ) effect on forage portions (grasses + legumes) and grasses. Crude protein and in vitro dry matter digestible yield of pasture forage portions were not significantly ( P &gt; 0.05 ) influenced by the rate and time of 2, 4-D application and their interaction. Weed dry matter yield was significantly affected by the interaction of rate and time of 2, 4-D application and mid-July application at 1.5 and 2 L·ha−1 gave the lowest yield. Therefore, to produce optimum quality and quantity of forage from natural pasture, the application of 2, 4-D in mid-July at 1.5 L·ha−1 is recommended.