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Soybean Tolerance To Ultra-Low Doses Of Dicamba: Hormesis Or Not, Luka Milosevic, O. Adewale Osipitan, Jon E. Scott, Stevan Z. Knezevic

Department of Agronomy and Horticulture: Faculty Publications

The widespread use of dicamba across the soybean growing regions of the United States resulted in increased off-target movement of this herbicide to susceptible vegetations. There are speculations that a drift of sublethal (ultra-low) doses of dicamba can enhance soybean growth and yield through a phenomenon called hormesis. Field studies were conducted during 2018 and 2019 to determine whether soybean growth and yield can be enhanced with ultra-low doses (0.0112–56 g ae ha^-1) of dicamba, applied at three growth stages (V2, R1 and R2). There was no evidence that the ultra-low doses of dicamba (0.0112–56 g ae ha …

Characterization And Management Of Auxin-Resistant Palmer Amaranth In Tennessee, Delaney C. Foster

Doctoral Dissertations

Palmer amaranth has a long history of evolving resistance to herbicides to the point it has become a significant row crop production obstacle. Cotton and soybean growers were offered new technologies in 2016, expanding in-crop herbicide options to include dicamba or 2,4-D. Within three years of commercialization, dicamba use in these crops increased ten-fold and growers began to report Palmer amaranth escapes in west Tennessee auxin-tolerant production systems. A survey of Palmer amaranth escapes in dicamba and 2,4-D-tolerant cotton and soybean fields in Tennessee was conducted in the fall of 2021 with the objective of determining if poor control was …

Vegetation And Animal Production In Pastures Sprayed For Western Ragweed Control, Keith Harmoney, John Jaeger

Kansas Agricultural Experiment Station Research Reports

Western ragweed (Ambrosia psilostachya) is a common native forb found throughout Kansas native rangelands and in some seeded pastures. Over time, western ragweed can form dense colonies from growth of lateral creeping rootstalks with multiple buds that can initiate new growth and form an upright stem and plant. Past research has shown that western ragweed does not compete with native grass production until ragweed contributes over approximately 35% of the forage dry matter of a pasture area. Cattle have utilized western ragweed in past long-term historical grazing trials. In a previous long-term trial at Hays, KS, western ragweed …

Reclaiming Old World Bluestem Pasture With Imazapyr Application And Native Grass Overseeding, Keith Harmoney

Kansas Agricultural Experiment Station Research Reports

Old world bluestems (OWB), mainly Caucasian bluestem (Bothriochloa bladhii) and yellow bluestem(Bothriochloa ischaemum)introduced from parts of eastern Europe, Asia, Africa, and Australia, have been shown to reduce abundance and diversity of some insect and wildlife species compared to native grasses when these OWB grasses form dense stands. These OWBs have been invading native pastures in the southern Great Plains and are rapidly increasing in the amount of area occupied in Kansas. Two landowners purchased pasture property in Ellsworth County, KS, and observed that Caucasian old world bluestem had increased in the pasture significantly over the course …

Optimization And Resistance Mitigation Of Dicamba And Glufosinate In Xtendflex® Crops, Grant Lawson Priess

Graduate Theses and Dissertations

The commercial launch of XtendFlex® crops enabled the use of dicamba, glufosinate, and glyphosate in-season. Utilizing herbicides that target different sites of action within troublesome weeds has been a tactic proposed to mitigate the likelihood of target-site resistance evolving; however, if interactions of the herbicides are detrimental to control of weedy species the likelihood of metabolic resistance increases. The objective of this research was to: 1) optimize efficacy and economic benefits of dicamba, glufosinate, and glyphosate; 2) characterize any interactions that were observed; 3) understand the mechanisms responsible for the reductions in weed control; 4) attempt to overcome interactions that …

Relative Soybean Response To Aminocyclopyrachlor, 2,4-D, Dicamba, And Aminopyralid, Trey I. Clark

Masters Theses

This research compared the visual symptomology of four auxin herbicides applied at three rates to simulate tank contamination on non-auxin tolerant soybeans. The herbicides examined were aminocyclopyrachlor (ACP), 2,4-D, dicamba, and aminopyralid. The standard labeled rates (SLR) used to base the application rates were 0.12 kg ae ha^-1 for ACP and aminopyralid while dicamba and 2,4-D used 1.12 kg ae ha^-1. These four herbicides exhibit similar symptoms on soybeans which is problematic when diagnosing soybean response. One goal of this project was to obtain high-quality images of the four herbicide’s effect on soybeans, with the hope of …

Effects Of Micro-Rates Of 2,4-D And Dicamba On Lettuce And Pumpkin In Nebraska, Xinzheng Chen

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Off-target herbicide injury from dicamba and 2,4-D is an increasingly common problem for specialty crop growers in the Midwestern United States. Both lettuce (Lactuca sativa L.) and pumpkin (Cucurbita spp.) are common specialty crops grown in Nebraska, and their proximity to corn and soybean production makes these crops susceptible to herbicide drift injury and yield loss. The objectives of this thesis research was to quantify crop injury and yield loss in greenhouse- and field-grown lettuce and field-grown pumpkins at different growth stages after exposure to sub-lethal doses of dicamba or 2,4-D. Dose response curves were generated to determine effective dose …

Characterization And Management Of Glyphosate-Resistant Junglerice, Clay M. Perkins

Doctoral Dissertations

Junglerice has become a major weed in Tennessee and across the mid-south. Glyphosate resistance and dicamba antagonism has resulted in the reported control failures and rise in prevalence. Junglerice was the most prevalent weed escape in cotton and soybean fields across Tennessee from 2018 to 2020. In all, 13% of the junglerice accessions could no longer be effectively controlled with glyphosate. Due to poor in-crop control, it has been recommended to start clean when trying to control junglerice and other grasses. Therefore, research was conducted to determine the best burndown methods utilizing dicamba, glufosinate, or paraquat. A sequential application of …

Crop Response To Low-Dose Dicamba, Mason Castner

Graduate Theses and Dissertations

The introduction of dicamba-resistant (DR) soybean [Glycine max (L.) Merr.] and cotton (Gossypium hirsutum L.) followed by a label allowing over-the-top applications of dicamba in the 2017 provided growers an additional option for broadleaf weed control. Because non-DR soybean is sensitive to low concentrations of dicamba, postemergence dicamba applications present growers choosing to plant non-DR soybean with concerns of damage from off-target movement through physical drift and volatilization of the herbicide as well as tank-contamination from prior dicamba application. Consequences of low-dose dicamba exposure on sensitive vegetative and reproductive soybean have been well researched, but little is known regarding the …

Effect Of Tank-Mixing Glyphosate, Dicamba, And Graminicides On Grass Weed Control In Roundup Ready 2 Xtend Soybeans, R. Liu, I. Effertz, T. Lambert, A. Jhala, V. Kumar

Kansas Agricultural Experiment Station Research Reports

The adoption of Roundup Ready 2 Xtendsoybean allows growers to use dicamba (Xtendimax or Engenia) in mixtures with glyphosate (Roundup PowerMax) or graminicides (Select Max or Assure II) for broad spectrum weed control. However, anecdotal evidence suggests that Xtendimax may cause antagonism when applied with Select Max and/or Assure II herbicides. The main objective of this study was to determine the effectiveness of Roundup PowerMax, Select Max, and/or Assure II alone or in tank-mixtures with Xtendimax for grass weed control in Xtendsoybean. Field studies were conducted in 2020 at the Kansas State University Agricultural Research Center (KSU-ARC) near Hays, KS, …

Effects Of Tank Contamination And Impact Of Drift-Reducing Agents On Weed Control In Response To Dicamba Applications, Milos Zaric

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Availability of dicamba-tolerant (DT) crops from 2017 provided farmers with additional herbicides for weed control management in row crops. However, the technology alike this one has concerns regarding dicamba off-target movement (OTM) causing undesirable effects on sensitive vegetation. Even though dicamba has high water solubility OTM that has often been overlooked when it comes to unintended crop exposure is dicamba tank contamination. Considering the complexity of spraying equipment soybean response may be expected even when small amounts of residues are left in the spray equipment. Typically, the same field spray equipment is used to perform herbicide application through growing season …

Sensitivity Of Enlisttm And Roundup Ready Xtend® Technologies To Auxin Herbicides And Comparison Of Resistance To Susceptible Cotton And Soybean Cultivars, James Rose

Graduate Theses and Dissertations

Increases in weed resistance have led to the development of new herbicide-resistant crop technologies, namely the Roundup Ready Xtend® and EnlistTM weed control systems. These new technologies provide resistance to applications of the synthetic auxins dicamba or 2,4-D, respectively, in traited cotton or soybean. It is unknown if there is any resistance to other herbicides within the synthetic auxin group (WSSA Group 4) in these traited crops. Experiments were conducted with auxin herbicides representing all five families within WSSA Group 4. Herbicides were applied either preemergence (PRE) or postemergence (POST) relative to the crop in a single application. Applications were …

Control Of Volunteer Corn In Enlist Corn And Economics Of Herbicide Programs For Weed Control In Conventional And Multiple Herbicide-Resistant Soybean Across Nebraska, Adam M. Striegel

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

With commercialization of multiple herbicide-resistant corn and soybean cultivars, producers have new management options for controlling herbicide-resistant weeds and volunteer corn. Corn-on-corn production systems are common in irrigated fields in southcentral Nebraska which can create issues with volunteer corn management in corn fields. Enlist corn contains a new multiple herbicide-resistant trait providing resistance to 2,4-D choline, glyphosate, and the aryloxyphenoxypropionate (FOPs). Field experiments were conducted in 2018 and 2019 at South Central Agricultural Laboratory near Clay Center, Nebraska with the objective to evaluate ACCase-inhibiting herbicides and herbicide application timing on volunteer corn control, Enlist corn injury, and yield. Glyphosate/glufosinate-resistant corn …

Herbicide Injury From Dicamba And 2,4-D: How Much Is Too Much In Lettuce?, Xinzheng Chen, Amit J. Jhala, Stevan Z. Knezevic, Samuel E. Wortman

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Off-target herbicide injury from dicamba and 2,4-D is an increasingly common problem for specialty crop growers in the Midwest U.S. Lettuce (Lactuca sativa L.) is a common specialty crops grown in Nebraska, but proximity to corn and soybean production leaves growers vulnerable to crop injury and significant economic loss. The goal of this study was to quantify crop injury and yield loss in greenhouse grown lettuce after exposure to simulated sub-lethal drift rates of 2,4-D and dicamba. Sublethal doses were determined based on a percentage of the maximum labeled rate and ranged from 25% to 0.01%. Tested lettuce cultivars …

Glyphosate Plus Dicamba Spray Solution Deposition, Coverage, And Efficacy As Influenced By Spray Nozzle Design And Weed Density, Madison Dru Kramer

Theses and Dissertations--Plant and Soil Sciences

Dicamba injury to sensitive soybean and other broadleaf crops due to drift is a major issue and label restrictions have been created to mitigate dicamba drift. One restriction is the mandated use of low drift nozzles to spray dicamba; these nozzles produce larger droplets and minimize the production of driftable fines. Experiments were conducted to evaluate herbicide coverage, deposition, and efficacy. Three spray nozzle designs and different weed densities were the main factors in the analysis. Dicamba plus glyphosate was applied to 5 to 10 cm tall weeds with a Turbo TeeJet (TT11005) nozzle and two drift reduction nozzles approved …

Evaluation Of The Influence Of Dicamba Exposure On Crop Injury And Canopy Closure Of Glufosinate Resistant Soybean, Zachary K. Perry

Theses and Dissertations--Plant and Soil Sciences

Dicamba-resistant soybean along with lower volatility dicamba formulations have been introduced in an attempt to control herbicide resistant weeds such as Amaranthus palmeri. This introduction has increased the amount of dicamba being applied later in the growing season increasing the prevalence of dicamba off-target movement. Dicamba damage was simulated by applying low rates of dicamba directly on soybeans at rates (0.5 g ae ha^-1, 1 g ae ha^-1 and 5 g ae ha^-1 dicamba) and five-exposure timings from June 1 to July 10. The experimental design was a randomized complete block with four replications at …

Investigating Dicamba Tolerance In Grapevine Cultivars Through Drift Simulation Assays, Bryce David Bentley

MSU Graduate Theses

Dicamba is a synthetic auxin herbicide which acts systematically and selectively controls broadleaf plants and has become increasingly popular in the past several years for weed control in commercial agriculture following widespread adoption of dicamba-resistant, transgenic soybean and cotton. Dicamba may be better acknowledged by growers of specialty crops, like grapes, for its capacity to drift miles away from the site of application and deposit on fields, remaining potent enough to cause crop damage and yield loss to vulnerable plants. Grapes are among the most susceptible agronomic crops to dicamba drift, showing visible injury at rates less than 1% of …

Herbicide Strategies For Managing Glyphosate- And Dicamba-Resistant Kochia In Roundup Ready 2 Xtend Soybean, V. Kumar, R. Liu, T. Lambert, P. W. Stahlman

Kansas Agricultural Experiment Station Research Reports

Kochia populations with multiple resistance to glyphosate and dicamba are an increasing concern for growers in the High Plains region, including Kansas. A field study was conducted at the Kansas State University Agricultural Research Center near Hays, KS, to evaluate and develop herbicide options for controlling glyphosate- and dicamba-resistant kochia in Roundup Ready 2 Xtend soybean. The study site was uniformly infested with a glyphosate- and dicamba-resistant kochia population prior to soybean planting. Fifteen herbicide treatments (programs), including PRE alone and PRE followed by (fb) POST-applied herbicides, were investigated in a randomized complete block design with four replications. …

Integrating Cover Crops And Herbicides For Horseweed [Conyza Canadensis (L.) Cronq.] Management Prior To Soybean [Glycine Max (L.) Merr.], Austin Sherman

Theses and Dissertations--Plant and Soil Sciences

Horseweed (Conyza canadensis (L.) Cronq.) is prevalent in Kentucky and can be difficult to control. Research has shown multiple weed control methods to be more sustainable than relying on chemical control alone, so the use of multiple methods for horseweed management was examined in this study. The main objective was to determine best practice(s) to reduce horseweed prior to soybean [Glycine max (L.) Merr.]. Treatments included: fall-planted cover crop [CC; cereal rye (Secale cereale L.) or none], fall-applied herbicide (saflufenacil or none), and spring-applied herbicides (dicamba, 2,4-D ester, or none). We hypothesized horseweed densities would be reduced …

Synthesis Of Dicamba Glucosides For The Study Of Environmental Dicamba Drift Effects On Soybeans, Holly Wallace

Graduate Theses and Dissertations

The most popular herbicide used for weed control has been glyphosate for many years in the Midwestern United States. Plants have begun to develop a resistance to glyphosate due to over use of the herbicide. This herbicide resistance has pushed farmers to turn to alternative herbicides such as dicamba and 2,4-D. Recently agrochemical companies have developed genetically modified crops that are resistant to herbicides such as dicamba. These modified crops allow farmers to spray their fields with dicamba without fear of crop damage. Farmers of non-genetically modified crops, however, suffer damage and loss of yield from herbicide drift effects of …

Soybean Response To Dicamba: Associated Injury Criteria And Development Of A Model To Predict Yield Loss, Matthew Ryan Foster

LSU Doctoral Dissertations

In research conducted using indeterminate soybean [Glycine max (L.) Merr.], fourteen injury criteria observed following dicamba at 0.6 to 280 g ae ha^-1 (1/1000 to ½ of 560 g ha^-1 use rate) were rated using a scale of 0= no injury, 1= slight, 2= slight to moderate, 3= moderate, 4= moderate to severe, and 5= severe. Greatest crop injury 15 d after treatment (DAT) was observed following dicamba applied at 0.6 to 4.4 g ha^-1 at V3/V4 for upper canopy pale leaf margins (3.8 to 4.2) and at R1/R2 for terminal leaf cupping (4.1 to 5.0) …

Dicamba Effects On Soybean (Glycine Max) Growth, Yield, And Offspring, Mark Spencer Mccown

Graduate Theses and Dissertations

Introduction of a new dicamba-resistant (Xtend) trait in soybean and cotton will increase dicamba herbicide use. Consequently, concern for injury to sensitive crops from off-target movement and tank contamination will likely increase. For soybean, foliar symptoms associated with dicamba damage do not necessarily reflect yield losses; hence, experiments were conducted to determine the effects of dicamba on soybean growth, yield, and offspring. Low rates of dicamba [1/64X (8.75 g ae ha-1) and 1/256X (2.18 g ae ha-1) of a normal 1X field rate (560 g ae ha-1)] were applied at two vegetative growth stages (V4, V6) and at each reproductive …

Evaluation Of Dicamba Off-Target Movement And Subsequent Effects On Soybean Offspring, Gordon Travis Jones

Graduate Theses and Dissertations

Commercial launch of cotton with resistance to dicamba, glyphosate, and glufosinate occurred in 2015 and launch of soybean with resistance to dicamba and glyphosate occurred in early 2016. It is likely that non-dicamba-resistant soybean will be planted in close proximity to dicamba-resistant soybean and cotton. Therefore, experiments were conducted to examine the distance dicamba moves during an application using commercial application equipment, as well as the effect the drift events have upon soybean offspring. Additional experiments were designed to investigate the effect glyphosate addition to dicamba has upon soybean growth and yield as well as possible effects on offspring. Lastly, …

Integrating Half Rates Of Dicamba And Atrazine With Increasing Sorghum Density And Nitrogen Rate For Palmer Amaranth Control, I. B. Cuvaca, A. J. Foster, R. Currie

Kansas Agricultural Experiment Station Research Reports

Sorghum is an important crop in Kansas. However, in-season weed control options for sorghum are limited. This limitation is exacerbated by Palmer amaranth season-long interference and resistance to multiple herbicide modes of action.

This 2-year study investigated the ability of a contrasting combination of cultural and chemical practices to control Palmer amaranth while maintaining or improving sorghum grain yield. Particular research emphasis was to evaluate the effect(s) of integrating half rates of dicamba and atrazine applied as PRE with increasing sorghum density and nitrogen rate on Palmer amaranth control and grain yield in an irrigated environment.

Palmer Amaranth (Amaranthus Palmeri) Suppression With Half Rates Of Dicamba And Atrazine With Increasing Sorghum (Sorghum Bicolor) Density And Nitrogen Rate, I. B. Cuvaca, R. Currie, A. J. Foster

Kansas Agricultural Experiment Station Research Reports

Palmer amaranth (PA) competition can result in severe yield loss in grain sorghum. Increasing sorghum density and nutrient supply could promote early/rapid canopy closure and therefore reduce the amount of light that could otherwise penetrate the canopy and promote PA growth in sorghum. A study was conducted at the Southwest Research-Extension Center near Garden City, KS, to determine if PA could be suppressed with dicamba and atrazine applied as PRE at half rates combined with increasing sorghum density (60,000, 90,000, and 120,000 seeds/a), and nitrogen rate (0, 100, 200 lb/a). Preliminary results indicate that increasing plant density and nitrogen rate …

Palmer Amaranth (Amaranthus Palmeri) Suppression With Half Rates Of Dicamba And Atrazine With Increasing Sorghum (Sorghum Bicolor) Density And Nitrogen Rate, I. B. Cuvaca, R. Currie, A. J. Foster

Kansas Agricultural Experiment Station Research Reports

Palmer amaranth (PA) competition can result in severe yield loss in grain sorghum. Increasing sorghum density and nutrient supply could promote early/rapid canopy closure and therefore reduce the amount of light that could otherwise penetrate the canopy and promote PA growth in sorghum. A study was conducted at the Southwest Research-Extension Center near Garden City, KS, to determine if PA could be suppressed with dicamba and atrazine applied as PRE at half rates combined with increasing sorghum density (60,000, 90,000, and 120,000 seeds/a), and nitrogen rate (0, 100, 200 lb/a). Preliminary results indicate that increasing plant density and nitrogen rate …

Fallow Weed Control With Preemergence Applications Of Balance Pro, Corvus, Banvel, Atrazine, And Authority Mtz, R. Currie, P. Geier

Kansas Agricultural Experiment Station Research Reports

Atrazine alone applied in the fall was less effective for kochia and Russian thistle control than other fall- or spring-applied herbicides in early summer. In mid season, control of kochia and Russian thistle was 85% or less with all fall-applied herbicides. Banvel (dicamba) increased kochia control when added to Balance Pro (isoxaflutole), plus Autumn Super (iodosulfuron + thiencarbazone), plus atrazine applied in the spring at mid season. All other spring herbicides were similar for kochia control. Russian thistle control was similar among all spring-applied herbicides except atrazine plus Banvel.

Fallow Weed Control With Preemergence Applications Of Clarity, Atrazine, Spartan Guard, Sharpen, Zidua, And Corvus, R. Currie, P. Geier

Kansas Agricultural Experiment Station Research Reports

Kochia control at 8 weeks after spring application (WAST) was greatest when Clar­ity (dicamba) was included in the spring applications or when Corvus (isoxaflutole + thiencarbazone) was applied with atrazine and Clarity in the fall. The best kochia con­trol at 13 WAST occurred with spring applications containing Clarity. Only Clarity plus Atrazine, Sharpen, Zidua, Spartan Guard, or Corvus applied in the spring provided as much as 90% kochia control at 20 WAST. Only the spring application of Spartan Guard and Clarity controlled Russian thistle 90% at 20 WAST.

Weed Control With Accent, Callisto, Isoxadifen, Impact, Cinch, Dicamba, And Atrazine In Irrigated Corn, R. Currie, P. Geier

Kansas Agricultural Experiment Station Research Reports

Some timings and combinations of the herbicides tested in this study controlled Palmer amaranth, kochia, quinoa, Russian thistle, and green foxtail from 95 to 100% 51 days after postemergence application (DA-B). Accent (nicosulfuron) plus Callisto (mesotri­one) and isoxadifen alone postemergence provided 88% Palmer amaranth control at 51 DA-B. Kochia control was 92 and 90% when Accent plus Callisto and isoxadifen alone or with atrazine and Dicamba XP (dicamba) was applied postemergence following Cinch (S-metolachlor) preemergence application. Crabgrass control with preemergence followed by postemergence treatments exceeded 89%. Crabgrass control was 83 and 88% when no preemergence herbicide was applied …

Efficacy Of Preemergence And Sequential Applications With Corvus, Atrazine, Starane, Balance, Anthem, Capreno, Diflexx And Halex Gt In Irrigated Corn, R. Currie, P. Geier

Kansas Agricultural Experiment Station Research Reports

Control of kochia and quinoa was 98 to 100% regardless of herbicide treatment at 48 days after post applications (DAPT), and 95% or more with all herbicides for Russian thistle. Palmer amaranth control was slightly less with preemergent (PRE) treatments alone compared to sequential treatments. Corvus (isoxaflutole + thiencarbazone) plus atrazine, Starane Ultra (fluroxypyr), and nonionic surfactant preemergence controlled crabgrass by 88%; whereas all other treatments provided 91% or more crabgrass control. Corn with the best herbicide treatments yielded 33 to 66 bu/a more than untreated corn.