Download or read book Glyphosate Resistant Palmer Amaranth amaranthus Palmeri Management Late season and Post harvest in Corn Production Systems written by Whitney Desiree Crow and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of this research were to evaluate control options for glyphosate resistant (GR) Palmer amaranth (Amaranthus palmeri) latelate-season in corn systems and POST-harvest for the prevention of seed production. Our results determined that the best late-season control methods were treatments tank-mixed with dicamba plus diflufenzopyr. These tank-mixtures improved control from 10 to 46% [percent] over treatments without the dicamba premix. Tankmixtures with dicamba plus diflufenzopyr that provided weed control > [greater than] 96% 28 DAA included s-metolachlor plus glyphosate plus mesotrione and tembotrione plus thiencarbazone. For the prevention of POST-harvest GR palmer amaranth seed production, our results determined that paraquat provides excellent initial control of existing vegetation but regrowth can occur from larger plants. The addition of a residual herbicide may aid in controlling regrowth as well as preventing plant germination. All treatments provided enough control for the prevention of seed production. Through implementation of POST-harvest management practices, 1200 seed per m2 [meter squared] was prevented from replenishing the soil seed bank. There were no adverse affects on wheat yield. From these results, we can conclude that when practicing POST only weed management strategies, application timing is vital for the prevention of corn loss and that implementation of late-season weed management programs can effectively reduce weed seed rain, therefore reducing weed seed bank densities.

Download or read book Biology and Management of Multiple glyphosate Als and Atrazine Resistant Palmer Amaranth in Michigan written by Jonathon Kohrt and published by . This book was released on 2017 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Palmer Amaranth Amaranthus Palmeri Control in Double crop Dicamba glyphosate Resistant Soybean Glycine Max and Dicamba and 2 4 D Efficacy on Palmer Amaranth and Common Waterhemp Amaranthus Rudis written by Nathaniel Russell Thompson and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Auxin herbicides have been widely used for broadleaf weed control since the mid-1940's. With new auxinic herbicide-resistant traits in corn, soybean, and cotton, use of these herbicides is likely to increase. Glyphosate-resistant Palmer amaranth (Amaranthus palmeri) and common waterhemp (Amaranthus rudis) are two primary problematic weed species that will be targeted with dicamba and 2,4-D in the new systems. No-till double-crop soybean after winter wheat harvest is a popular cropping system in central and eastern Kansas, however, management of glyphosate resistant Palmer amaranth has become a serious issue. Field experiments were established near Manhattan and Hutchinson, KS, in 2016 and 2017, to compare seventeen herbicide treatments for control of Palmer amaranth and large crabgrass (Digitaria sanguinalis) in dicamba/glyphosate resistant no-till double-crop soybean after winter wheat. Herbicide programs that included a residual preemergence (PRE) treatment followed by a postemergence (POST) treatment offered greater Palmer amaranth control 8 weeks after planting when compared to PRE-only, POST-only and burndown-only treatments. All treatments that contained glyphosate POST provided complete control of large crabgrass compared to less than 43% control with PRE-only treatments. Soybean grain yield was greater in programs that included PRE followed by POST treatments, compared to PRE-only and burndown-only treatments. A second set of field experiments were established in 2017 near Manhattan and Ottawa, KS to evaluate dicamba and 2,4-D POST efficacy on Palmer amaranth and common waterhemp. Five rates of dicamba (140, 280, 560, 1121, and 2242 g ae ha−1) and 2,4-D (140, 280, 560, 1121, and 2242 g ae ha−1) were used to evaluate control of the Amaranthus spp. Each experiment was conducted twice at each location. Dicamba provided better Palmer amaranth and common waterhemp control than 2,4-D across the rates evaluated. Control of Palmer amaranth was 94% and 99% with dicamba rates of 1121 and 2242 g ae ha−1, respectively, but 2,4-D never provided more than 80% control at any rate. The highest rates of both dicamba and 2,4-D provided greater than 91% common waterhemp control, but control was less than 78% with all other rates of both herbicides. Palmer amaranth and common waterhemp control did not exceed 73% with the highest labelled POST rates of either dicamba or 2,4-D. Auxinic herbicide-resistant traits in corn, soybean, and cotton offer new options for controlling glyphosate-resistant Palmer amaranth and common waterhemp, however proper stewardship is vital to maintain their effectiveness.

Download or read book Herbicide Resistant Palmer Amaranth Amaranthus Palmeri S Wats in the United States Mechanisms of Resistance Impact and Management written by Parminder S. Chahal and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Palmer amaranth, a dioecious summer annual species, is one of the most troublesome weeds in the agronomic crop production systems in the United States. In the last two decades, continuous reliance on herbicide(s) with the same mode of action as the sole weed management strategy has resulted in the evolution of herbicide-resistant (HR) weeds, including Palmer amaranth. By 2015, Palmer amaranth biotypes had been confirmed resistant to acetolactate synthase (ALS)-inhibitors, dinitroanilines, glyphosate, hydroxyphenylpyruvate dioxygenase (HPPD)-inhibitors, and triazine herbicides in some parts of the United States along with multiple HR biotypes. Mechanisms of herbicide-resistance in Palmer amaranth are discussed in this chapter. Preplant herbicide options including glufosinate, 2,4-D, and dicamba provide excellent Palmer amaranth control; however, their application is limited before planting crops, which is often not possible due to unfavorable weather conditions. Agricultural biotechnology companies are developing new multiple HR crops that will allow the post-emergence application of respective herbicides for management of HR weeds, including Palmer amaranth. For the effective in-crop management of Palmer amaranth, and to reduce the potential for the evolution of other HR weeds, growers should apply herbicides with different modes of action in tank-mixture and should also incorporate cultural practices including inversion tillage and cover crops along with herbicide programs.

Download or read book Characterization and Management of PPO and Glyphosate Resistant Palmer Amaranth written by Drake Copeland and published by . This book was released on 2018 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research was conducted from the fall of 2016 to the fall of 2018 to characterize and manage PPO- and glyphosate-resistant Palmer amaranth (Amaranthus palmeri S. Wats). Studies included a multi-county survey to determine the prevalence of PPO-resistant Palmer amaranth biotypes and the PPX2 mutations that confer PPO resistance, an in-field evaluation of control of PPO-resistant and PPO-susceptible Palmer amaranth populations with herbicide treatments applied at either sunrise or midday, and field studies that evaluated cover crop termination for control of Palmer amaranth in Roundup Ready Xtend® and Liberty Link® soybean systems [(Glycine max (L.) Merr.]. Results from this research indicate that PPO-resistant Palmer amaranth infests roughly 80% of west Tennessee fields, at least two herbicides with different, effective sites of action should be applied timely for POST herbicidal control of PPO-resistant Palmer amaranth, and that delaying cover crop termination in both Roundup Ready Xtend® and Liberty Link® soybeans can effectively reduce in-season POST applications and maximize Palmer amaranth control if the correct residual herbicide is included at planting timing.

Download or read book Integration of Herbicide Programs with Cultural and Mechanical Practices for Managing Glyphosate resistant Palmer Amaranth amaranthus Palmeri in Soybean glycine Max written by Holden Douglas Bell and published by . This book was released on 2014 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Herbicide-resistant Palmer amaranth is the most troublesome weed in Arkansas row crops, causing producers to rely heavily on multiple mechanisms of action to reduce selection pressure for further evolution of herbicide resistance and to successfully produce a profitable crop. It is critical for the sustainability of weed management not only to adequately control this weed but also to reduce the soil seedbank using both non-chemical and chemical practices. Studies were conducted to determine the effect of soybean row spacing, seeding rate, and herbicide program on Palmer amaranth emergence, survival, and seed production in soybean, the effect of drill-seeded soybean population on Palmer amaranth emergence with and without a residual preemergence (PRE)-applied herbicide, and the impact of integrating cover crops and deep tillage with herbicide programs for glyphosate-resistant Palmer amaranth control in glyphosate- and glufosinate-resistant soybean. Herbicide application timing and choice of herbicide had more of an impact on Palmer amaranth control than either row spacing or seeding rate and greater control was observed in PRE plus postemergence (POST)-applied residual programs compared to POST-only residual programs, regardless of seeding rate and row spacing. Narrow-row soybean reached 95% canopy formation quicker than plants in wide rows, in turn resulting in greater suppression of Palmer amaranth emergence. In drill-seeded soybean, a PRE-applied residual herbicide was more beneficial in reducing Palmer amaranth emergence than increasing soybean density. Using a combination of cover crop and deep tillage along with the addition of a PRE followed by POST-applied residual herbicide program, Palmer amaranth was effectively controlled throughout the season with limited weed seed return to the soil seedbank in both glufosinate- and glyphosate-resistant soybean. Overall, herbicide programs were the strongest factor influencing Palmer amaranth control; however, the addition of a cover crop, deep tillage, and narrow row spacing play a vital role in reducing selection pressure on herbicides, thus reducing risks for new cases of herbicide resistance.

Download or read book Integration and Management of Winter annual Cover Crops and Herbicides to Control Glyphosate resistant Palmer Amaranth Amaranthus Palmeri S Wats written by Matthew Scott Wiggins and published by . This book was released on 2014 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this research was to evaluate the integration of high residue winter-annual cover crops with herbicides, both preemergence and postemergence, to control glyphosate-resistant Palmer amaranth. The results of these trials indicated that winter-annual cover crops improved early-season weed suppression. However, cover crops alone or as part of an integrated weed management system including only preemergence or only postemergence herbicides was not sufficient to control of glyphosate-resistant Palmer amaranth. Therefore, winter-annual cover crops should be used in conjunction with existing weed control tactics to achieve adequate glyphosate-resistant Palmer amaranth control, where applicable.

Download or read book Physiological Basis of Herbicide Interaction and Integrated Management of Palmer Amaranth Amaranthus Palmeri written by Ivan Bernardo Cuvaca and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Palmer amaranth is a major threat to many cropping systems in the USA. As a result of selection, Palmer amaranth has evolved resistance to at least six herbicide modes of action including microtubule-, 5-enolpyruvylshikimate-3-phosphate synthase-, acetolactate synthase-, photosystem II-, hydroxyphenylpyruvate dioxygenase-, and protoporphyrinogen oxidase- inhibitors. Dicamba is effective for Palmer amaranth control; however, extensive use of this herbicide increases the likelihood of evolution of resistance to dicamba. The overall objective of this dissertation was to investigate the physiological basis of interaction of herbicides with different modes of action in Palmer amaranth control and evaluate use of integrated approaches to manage Palmer amaranth in field conditions. The specific objectives were to: 1) evaluate the effect of plant height on dicamba efficacy to control Palmer amaranth; 2) investigate the mechanism of resistance to glyphosate in a Palmer amaranth accession from Kansas, and evaluate efficacy of glyphosate and dicamba tank-mix to control this accession; 3) investigate the physiological basis of glyphosate and dicamba interaction in tank-mix to control Palmer amaranth; 4) determine the efficacy of reduced dicamba use on Palmer amaranth control in irrigated corn production; and 5) investigate grain sorghum and Palmer amaranth growth and reproductive attributes in response to sorghum density and nitrogen rate under irrigated conditions. All experiments were repeated and appropriate statistical tests were used for data analyses. The results indicate: a) increased absorption and translocation of dicamba contribute to increased efficacy to control Palmer amaranth at early growth stage; b) tank mixing glyphosate and dicamba had a synergistic effect on Palmer amaranth control; c) rapid absorption of dicamba and increased translocation of glyphosate resulted in increased Palmer amaranth control when applied in combination; d) there is an opportunity to maintain grain yield while effectively controlling Palmer amaranth in irrigated corn with the integration of increased corn plant population density and reduced dicamba application and e) integrating sorghum plant population and nitrogen did not suppress Palmer amaranth in irrigated sorghum, although sorghum grain yield was maintained. The outcome of this dissertation provides several strategies to improve control of Palmer amaranth.

Download or read book Response of Glyphosate Resistant Palmer Amaranth Amaranthus Palmeri to Protoporphyrinogen Oxidase Inhibiting Herbicides in Tennessee written by Alinna Marie Umphres and published by . This book was released on 2017 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: In many agronomic cropping systems across the United States, Palmer amaranth (Amaranthus palmeri) is the most economic and troublesome weed for producers. The introduction of glyphosate resistant (GR) crops gave producers the benefit of controlling Palmer amaranth as well as other weeds, a broad window of application, and reduced tillage practices. With the confirmation of GR Palmer amaranth, producers implemented protoporphyrinogen oxidase (PPO or Protox)-inhibiting herbicides to control these populations in crops such as soybean [Glycine max (L.) Merr.] and cotton [Gossypium hirsutum (L.)]. However the continuous use of PPO herbicides has caused a shift in Palmer amaranth populations for PPO resistance. Therefore the scope of this study was to observe fomesafen response to four Palmer amaranth populations, determine the fomesafen resistance level, evaluate the effect of Palmer amaranth size on fomesafen efficacy, determine susceptibility to other foliar-applied herbicides, and evaluate the efficacy of four soil-applied PPO-inhibiting herbicides on PPO-resistant (PPO-R) and PPOsusceptible (PPO-S) Palmer amaranth populations. The PPO-S population was observed with 98% control however, fomesafen efficacy was reduced in SPA, LPA, and WPA populations with 24%, 4%, and 2% control, respectively at 14 days after treatment (DAT). The level of resistance for the PPO-R population SPA was 4-fold relative to the PPO-S population KPA. When determining the height of Palmer amaranth on fomesafen efficacy, control of SPA Sm, Md, and Lg sized plants was 62%, 49%, and 18%, respectively. Atrazine, glufosinate, and mesotrione were observed to have the greatest control (>70%) of the SPA population but resistant to glyphosate and chlorimuron. When subjected to soil-applied PPO herbicides, SPA showed reduced control with fomesafen and saflufenacil however greater control was observed with flumioxazin and sulfentrazone at 35 DAT.

Download or read book Basis of Atrazine and Mesotrione Synergirm Biology and Management of Palmer Amaranth Amaranthus Palmeri S Wats in Nebraska Field Corn written by Parminder Chahal and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Palmer amaranth, a dioecious summer annual weed species, is the most troublesome weed in agronomic crop production systems in the United States. The confirmation of Palmer amaranth resistant to Photosystem (PS) II- and 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibitor in south central Nebraska justify the need to study the biology and management of Palmer amaranth, and to determine the mechanism of atrazine resistance and basis of atrazine and mesotrione synergism in resistant Palmer amaranth biotype from Nebraska. The objectives of this research were to: (1) determine the mechanism of atrazine resistance and basis of atrazine and mesotrione synergism applied in tank-mixture for control of PS II- and HPPD-inhibitor-resistant Palmer amaranth biotype from Nebraska, (2) determine the effect of degree of water stress on growth, fecundity and seed germination of Palmer amaranth biotypes, (3) develop herbicide programs for management of PS II- and HPPD-inhibitor-resistant Palmer amaranth in conventional corn, and (4) develop herbicide programs for management of PS II- and HPPD-inhibitor-resistant Palmer amaranth in glufosinate-, and glyphosate-resistant corn. Increased absorption of mesotrione applied in a tank-mixture with atrazine could be the basis of atrazine and mesotrione synergism for control of susceptible as well as PS II- and HPPD-inhibitor-resistant Palmer amaranth. Atrazine resistance was conferred by enhanced atrazine metabolism, a non-target site resistance mechanism, via glutathione S-transferase (GST) conjugation. The study conducted to evaluate the effect of degree of water stress on Palmer amaranth growth and fecundity suggested that Palmer amaranth has ability to survive water stress conditions and can produce significant amount of seeds with minimum effect on germination. Palmer amaranth at 100, 75, and 50% field capacity (FC) produced similar number of leaves (588 to 670 plant--1 ), growth index (1.1 to 1.4 x 105 cm3 plant--1) and total leaf area (571 to 693 cm 2 plant--1); however, plants at 100% FC achieved maximum height of 178 cm compared to 124 and 88 cm at 75% and 50% FC, respectively. The field experiments conducted for management of Palmer amaranth in conventional, glyphosate, and glufosinate-resistant field corn demonstrated that most PRE followed by POST herbicide programs provided highest Palmer amaranth control, corn yield and net return.

Download or read book Glyphosate resistant Palmer Amaranth amaranthus Palmeri in Arkansas written by Griff Michael Griffith and published by . This book was released on 2013 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since 2000, there have been thirteen weed species confirmed resistant (R) to glyphosate in the United States, six of those resistant species are present in Arkansas. The goal of this research was to confirm and to determine the level of resistance in two R Palmer amaranth biotypes from Mississippi (MC-R) and Lincoln (LC-R) Counties, Arkansas, and one susceptible (S) biotype from Clarendon County, South Carolina, which had never been exposed to glyphosate. Shikimic acid concentration over time was significantly greater in the S biotype than both the MC-R and LC-R biotypes. The lethal dose required to kill 50% (LD50) of the population was 2,255 and 3,223 g ae ha -1 for the MC-R and LC-R biotypes, respectively, and it was hypothesized that the two Arkansas biotypes each had a different resistance mechanism. Results indicate metabolism of glyphosate to its major metabolite, aminomethylphosphonic acid (AMPA), was not responsible for resistance in any biotype. Reduced absorption in the LC-R and limited translocation from the treated leaf in the MC-R were at least partially responsible for the observed resistance to glyphosate. The LC-R biotype effectively colonized a field within two years of a single resistant female producing ̃20,000 seed. Cotton lint yield was reduced over 100 kg ha-1 by some densities of LC-R Palmer, depending on the soil and relative elevation in that region. Several resistant management options exist in cotton; however, results indicate that timely herbicide applications based off of Palmer amaranth size are required for effective season-long control and management of the soil seedbank.

Download or read book Distribution Biology and Management of Glyphosate resistant Palmer Amaranth in North Carolina written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The introduction of glyphosate-resistant (GR) crops allowed for the topical applications of the herbicide glyphosate. This herbicide revolutionized weed control and crop management. Widespread adoption of this technology and extensive use of glyphosate led to intense selection pressure for evolution of GR weeds. In 2005, GR Palmer amaranth was suspected in North Carolina. A survey detected GR populations in 49 of 290 fields sampled. ALS-inhibitor resistance was also detected in 52 fields. Five fields had populations exhibiting multiple resistance to both glyphosate and ALS-inhibitors. Experiments were conducted to determine the resistance mechanism of GR Palmer amaranth. A GR biotype exhibited a 20-fold level of resistance compared to a glyphosate-susceptible (GS) biotype. Shikimate accumulated in GS but not GR plants after glyphosate application. Maximum absorption was observed by 12 hours after treatment (HAT), and was similar among biotypes except at 6 HAT, where GS plants absorbed 67% more than GR plants. Distribution of 14C was similar among biotypes in (42%), above (30%), and below (22%) the treated leaf and in roots (6%). This work did not lead to a suggestion a resistance mechanism. Field experiments were conducted to develop management strategies for GR Palmer amaranth in cotton. One evaluated residual control of Palmer amaranth by various herbicides. Of herbicides typically applied PRE or pre-plant, fomesafen, flumioxazin, and pyrithiobac were most effective. Pyrithiobac and S-metolachlor were the most effective postemergence (POST) herbicides. Flumioxazin and prometryn plus trifloxysulfuron were the most effective options for postemergence-directed applications. Integration of these herbicides into glyphosate-based systems could increase Palmer amaranth control. An experiment was conducted to evaluate PRE herbicides in a season-long system. All PRE herbicides increased late-season control. Among individual herbicides, fomesafen and pyrithiobac were most e.

Download or read book Integrated Weed Management for Reduced Weed Infestations in Sustainable Cropping Systems written by Rodrigo Werle and published by Frontiers Media SA. This book was released on 2023-10-30 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Weeds pose a major challenge to the sustainability of agricultural production systems, causing significant crop yield, economic and environmental losses. Chemical weed control tactics play a major role in modern weed management, maintaining the productivity of diverse cropping systems, reducing yield losses and facilitating conservation agriculture. However, the over-reliance on chemical weed control has led to shifts in weed communities in agroecosystems which are now becoming dominated by high competitors and herbicide resistance. Thus, weed scientists and practitioners are urged to develop and incorporate innovative and feasible integrated weed management (IWM) systems that can reduce weed infestations and environmental impacts.

Download or read book Herbicides written by Andrew Price and published by BoD – Books on Demand. This book was released on 2015-11-26 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Herbicides are one of the most widely used groups of pesticides worldwide for controlling weedy species in agricultural and non-crop settings. Due to the extensive use of herbicides and their value in weed management, herbicide research remains crucial for ensuring continued effective use of herbicides. Presently, a wide range of research continues to focus on improved herbicide use and weed biology. The authors of Herbicides, Agronomic Crops and Weed Biology cover multiple topics concerning current valuable herbicide research.

Download or read book Evaluating Evapotranspiration and Management of Glyphosate resistant Palmer Amaranth Amarnthus Palmeri S Watson written by Jasmine M. Mausbach and published by . This book was released on 2021 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Palmer amaranth (PA) is the most problematic weed in agronomic cropping systems in the United States. Acetolactate synthase (ALS) inhibitor-/glyphosate-resistant (GR) PA has been confirmed in Nebraska and is widespread in several counties. Soybean resistant to isoxaflutole/glufosinate/glyphosate has been developed to provide additional herbicide sites of action for control of herbicide-resistant weeds. The objectives of this study were to evaluate herbicide programs for control of ALS inhibitor/GR PA and their effect on PA density and biomass, as well as soybean injury and yield in isoxaflutole/glufosinate/glyphosate-resistant soybean. A PRE herbicide fb glufosinate controlled PA 80%-99% 21 d after late-POST in 2018 and reduced density 89%-100% in 2018 and 58%-100% in 2019 at 14 d after early-POST. Weed-crop competition models offer a significant tool for understanding and predicting crop yield losses due to crop-weed interference. Within current empirical models, weed biological characteristics are unknown, which limits understanding of weed growth in competition with crops and how that competition affects crop growth parameters. The objective of this study was to determine the effect of center-pivot and subsurface drip irrigation on the average evapotranspiration (ETa) of PA grown in corn, soybean, and fallow in south central Nebraska. Results suggest irrigation affects subplot ETa differences early in the growing season, but crop system and progression of plant growth with available water have a greater effect on ETa differences than irrigation type later in the growing season. Thus, crop management will likely have greater effects on PA ETa values than irrigation practices alone. This study provides base data on weed evapotranspiration and its relation to weed morphological features for future use in mechanistic weed-crop competition models. Velvetleaf is another troublesome broadleaf weed that competes with agronomic crops for resources such as soil moisture. The objective of this study was to determine the effect of degree of water stress on the growth and fecundity of velvetleaf using soil moisture sensors under greenhouse conditions. The results of this study demonstrate that velvetleaf can survive ≥ 50% field capacity (FC) continuous water stress conditions, although with reduced leaf number, plant height, and growth index compared to 75% and 100% FC.

Download or read book Alternative Herbicide Control Options for Glyphosate resistant Palmer Amaranth amaranthus Palmeri written by George Macmillan Botha and published by . This book was released on 2012 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The occurrence of glyphosate-resistant (GR) Palmer amaranth has prompted a shift in weed management strategies worldwide. Studies were conducted with the aim to (1) establish and compare the degree of tolerance of GR Palmer amaranth populations; (2) assess the efficacy of glufosinate, tembotrione, 2,4-D or dicamba, applied alone or tank-mixed, on Palmer amaranth with higher tolerance to glufosinate in the greenhouse and corn field, and (3) establish the mechanism involved in the tolerance of Palmer amaranth to glufosinate. Tembotrione, 2,4-D, dicamba, and glufosinate applied at 1x controlled 80 to 100%, 98 to 100%, 84 to 100%, and 94 to 100% Palmer amaranth, respectively. Differential response of Palmer amaranth populations to the test herbicides existed. The potential of selecting for resistance was highest in tembotrione, followed by dicamba. In the tank mixture test, all herbicides applied individually at 1x rate controlled Pra-C population 99 to 100% in the greenhouse and 91 to 100% in the field study. In corn, the control in Pra-C, Mis-C, and STF-C populations was 33 to 54% for tembotrione, 68 to 89% for 2,4-D, and 96 to 100% for glufosinate applied at their commercial rates. The study showed that half rates of 2,4-D and glufosinate can be applied, only in combination, without significantly compromising Palmer amaranth control. The majority of glufosinate + tembotrione and some glufosinate + dicamba mixtures were not compatible; glufosinate + 2,4-D mixtures were generally additive and in few cases, synergistic. The reduced efficacy from antagonism was overcome by mixing 1x rates of the herbicides. Pra-C (tolerant) had 2-folds higher tolerance than Lee-A (susceptible), with LD50 values of 344 and 141 g ha-1, respectively. The basal activity of the tolerant population was 20% higher than that of the susceptible. Tolerance to glufosinate is certainly due to higher baseline activity of GS in the tolerant plants, which would require more herbicide molecule to cause substantial inhibition.

Download or read book Postemergence and Residual Control of Glyphosate resistant Palmer Amaranth Amaranthus Palmeri with Dicamba written by Clifford Blake Edwards and published by . This book was released on 2013 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: On-farm research was conducted in 2011 and 2012 to determine the postemergence and residual control by dicamba of glyphosate-resistant (GR) Palmer amaranth (Amaranthus palmeri S. Wats.). Preemergence dicamba at 0, 0.28, 0.56, and 1.1 kg ae ha−1 and 0.07 kg ae ha−1 flumioxazin was applied at 30, 15 and 0 days prior to planting. Postemergence dicamba at 0.28, 0.56, and 1.1 kg ae ha−1 with and without 0.84 kg ae ha−1 glyphosate was applied to 5, 10 and 15 cm Palmer amaranth. In addition, a greenhouse experiment was conducted in 2012 to evaluate and confirm the optimum rate for control of Palmer amaranth with a new formulation of dicamba (BAS 18322H). In the greenhouse, dicamba at 0.14, 0.28, 0.56, 1.1, and 2.2 kg ae ha−1 was applied to 5, 10, and 15 cm Palmer amaranth.