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Susceptibility of Palmer amaranth (Amaranthus palmeri) to herbicides in accessions collected from the North Carolina Coastal Plain
- Denis J. Mahoney, David L. Jordan, Nilda Roma-Burgos, Katherine M. Jennings, Ramon G. Leon, Matthew C. Vann, Wesley J. Everman, Charles W. Cahoon
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- Journal:
- Weed Science / Volume 68 / Issue 6 / November 2020
- Published online by Cambridge University Press:
- 01 September 2020, pp. 582-593
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Palmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase (ALS)-inhibiting herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated 3 wk after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populations surviving thifensulfuron-methyl application (Ala-122-Ser, Pro-197-Ser, Trp-574-Leu, and/or Ser-653-Asn), in addition to a new mutation (Ala-282-Asp) that requires further investigation. Forty-two populations had survivors after mesotrione application, with one population having 17% survival. Four populations survived fomesafen treatment, while none survived glufosinate. Dose–response studies showed an increase in fomesafen needed to kill 50% of two populations (LD50); however, these rates were far below the field use rate (less than 5 g ha−1). In two populations following mesotrione dose–response studies, a 2.4- to 3.3-fold increase was noted, with LD90 values approaching the field use rate (72.8 and 89.8 g ha−1). Screening of the progeny of individuals surviving mesotrione confirmed the presence of resistance alleles, as there were a higher number of survivors at the 1X rate compared with the parent population, confirming resistance to mesotrione. These data suggest A. palmeri resistant to chemistries other than glyphosate and thifensulfuron-methyl are present in NC, which highlights the need for weed management approaches to mitigate the evolution and spread of herbicide-resistant populations.
The influence of soybean population and POST herbicide application timing on in-season and subsequent-season Palmer amaranth (Amaranthus palmeri) control and economic returns
- Denis J. Mahoney, David L. Jordan, Andrew T. Hare, Nilda Roma-Burgos, Katherine M. Jennings, Ramon G. Leon, Matthew C. Vann, Wesley J. Everman, Charles W. Cahoon
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- Journal:
- Weed Technology / Volume 35 / Issue 1 / February 2021
- Published online by Cambridge University Press:
- 18 August 2020, pp. 106-112
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Overreliance on herbicides for weed control has led to the evolution of herbicide-resistant Palmer amaranth populations. Farm managers should consider the long-term consequences of their short-term management decisions, especially when considering the soil weed seedbank. The objectives of this research were to (1) determine how soybean population and POST herbicide application timing affects in-season Palmer amaranth control and soybean yield, and (2) how those variables influence Palmer amaranth densities and cotton yields the following season. Soybeans were planted (19-cm row spacing) at a low-, medium-, and high-density population (268,000, 546,000, and 778,000 plants ha–1, respectively). Fomesafen and clethodim (280 and 210 g ai ha–1, respectively) were applied at the VE, V1, or V2 to V3 soybean growth stage. Nontreated plots were also included to assess the effect of soybean population alone. The following season, cotton was planted into these plots so as to understand the effects of soybean planting population on Palmer amaranth densities in the subsequent crop. When an herbicide application occurred at the V1 or V2 to V3 soybean stage, weed control in the high-density soybean population increased 17% to 23% compared to the low-density population. Economic return was not influenced by soybean population and was increased 72% to 94% with herbicide application compared to no treatment. In the subsequent cotton crop, Palmer amaranth densities were 24% to 39% lower 3 wk after planting when following soybean sprayed with herbicides compared to soybean without herbicides. Additionally, Palmer amaranth densities in cotton were 19% lower when soybean was treated at the VE stage compared to later stages. Thus, increasing soybean population can improve Palmer amaranth control without adversely affecting economic returns and can reduce future weed densities. Reducing the weed seedbank and selection pressure from herbicides are critical in mitigating resistance evolution.
Evaluation of dicamba retention in spray tanks and its impact on flue-cured tobacco
- Matthew D. Inman, Matthew C. Vann, Loren R. Fisher, Travis W. Gannon, David L. Jordan, Katie M. Jennings
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- Journal:
- Weed Technology / Volume 35 / Issue 1 / February 2021
- Published online by Cambridge University Press:
- 09 July 2020, pp. 35-42
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In recent years, there has been increased use of dicamba due to the introduction of dicamba-resistant cotton and soybean in the United States. Therefore, there is a potential increase in off-target movement of dicamba and injury to sensitive crops. Flue-cured tobacco is extremely sensitive to auxin herbicides, particularly dicamba. In addition to yield loss, residue from drift or equipment contamination can have severe repercussions for the marketability of the crop. Studies were conducted in 2016, 2017, and 2018 in North Carolina to evaluate spray-tank cleanout efficiency of dicamba using various cleaning procedures. No difference in dicamba recovery was observed regardless of dicamba formulation and cleaning agent. Dicamba residue decreased with the number of rinses. There was no difference in dicamba residue recovered from the third rinse compared with residue from the tank after being refilled for subsequent tank use. Recovery ranged from 2% to 19% of the original concentration rate among the three rinses. Field studies were also conducted in 2018 to evaluate flue-cured tobacco response to reduced rates of dicamba ranging, from 1/5 to 1/10,000 of a labeled rate. Injury and yield reductions varied by environment and application timing. When exposed to 1/500 of a labeled rate at 7 and 11 wk after transplanting, tobacco injury ranged from 39% to 53% and 10% to 16% 24 days after application, respectively. The maximum yield reduction was 62%, with a 55% reduction in value when exposed to 112 g ha−1 of dicamba. Correlations showed significant relationships between crop injury assessment and yield and value reductions, with Pearson values ranging from 0.24 to 0.63. These data can provide guidance to growers and stakeholders and emphasize the need for diligent stewardship when using dicamba technology.
Flue-cured tobacco tolerance to S-metolachlor
- Andrew M. Clapp, Matthew C. Vann, Charles W. Cahoon, Jr., David L. Jordan, Loren R. Fisher, Matthew D. Inman
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- Journal:
- Weed Technology / Volume 34 / Issue 6 / December 2020
- Published online by Cambridge University Press:
- 30 June 2020, pp. 843-848
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Currently, there are seven herbicides labeled for U.S. tobacco production; however, additional modes of action are greatly needed in order to reduce the risk of herbicide resistance. Field experiments were conducted at five locations during the 2017 and 2018 growing seasons to evaluate flue-cured tobacco tolerance to S-metolachlor applied pretransplanting incorporated (PTI) and pretransplanting (PRETR) at 1.07 (1×) and 2.14 (2×) kg ai ha−1. Severe injury was observed 6 wk after transplanting at the Whiteville environment in 2017 when S-metolachlor was applied PTI. End-of-season plant heights from PTI treatments at Whiteville were likewise reduced by 9% to 29% compared with nontreated controls, although cured leaf yield and value were reduced only when S-metolachlor was applied PTI at the 2× rate. Severe growth reduction was also observed at the Kinston location in 2018 where S-metolachlor was applied at the 2× rate. End-of-season plant heights were reduced 11% (PTI, 2×) and 20% (PRETR, 2×) compared with nontreated control plants. Cured leaf yield was reduced in Kinston when S-metolachlor was applied PRETR at the 2× rate; however, treatments did not impact cured leaf quality or value. Visual injury and reductions in stalk height, yield, quality, and value were not observed at the other three locations. Ultimately, it appears that injury potential from S-metolachlor is promoted by coarse soil texture and high early-season precipitation close to transplanting, both of which were documented at the Whiteville and Kinston locations. To reduce plant injury and the negative impacts to leaf yield and value, application rates lower than 1.07 kg ha−1 may be required in these scenarios.
Influence of timing of Palmer amaranth control in dicamba-resistant cotton on yield and economic return
- Matthew D. Inman, David L. Jordan, Matthew C. Vann, Andrew T. Hare, Alan C. York, Charles W. Cahoon
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- Journal:
- Weed Technology / Volume 34 / Issue 5 / October 2020
- Published online by Cambridge University Press:
- 02 April 2020, pp. 682-688
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Glyphosate-resistant (GR) Palmer amaranth continues to be challenging to control across the U.S. cotton belt. Timely application of POST herbicides and herbicides applied at planting or during the season with residual activity are utilized routinely to control this weed. Although glyphosate controls large Palmer amaranth that is not GR, herbicides such as glufosinate used in resistance management programs for GR Palmer amaranth must be applied when weeds are small. Dicamba can complement both glyphosate and glufosinate in controlling GR and glyphosate-susceptible (GS) biotypes in resistant cultivars. Two studies were conducted to determine Palmer amaranth control, weed biomass, and cotton yield, as well as to estimate economic net return when herbicides were applied 2, 3, 4, and 5 wk after planting (WAP). In one experiment POST-only applications were made. In the second experiment PRE herbicides were included. In general, Palmer amaranth was controlled at least 98% by herbicides applied at least three times regardless of timing of application or herbicide sequence. Glyphosate plus dicamba applied at 4 and 5 WAP controlled Palmer amaranth similarly compared to three applications by 8 WAP; however, yield was reduced 23% because of early-season interference. The inclusion of PRE herbicides benefited treatments that did not include herbicides applied 2 or 3 WAP. Glyphosate plus dicamba applied as the only herbicides 5 WAP provided 69% control of Palmer amaranth. PRE herbicides increased control to 96% for this POST treatment. Economic returns were similar when three or more POST applications were applied, with or without PRE herbicides.
Glufosinate plus Dicamba for Rescue Palmer Amaranth Control in XtendFlexTM Cotton
- Rachel A. Vann, Alan C. York, Charles W. Cahoon, Jr, Trace B. Buck, Matthew C. Askew, Richard W. Seagroves
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- Journal:
- Weed Technology / Volume 31 / Issue 5 / October 2017
- Published online by Cambridge University Press:
- 02 October 2017, pp. 666-674
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Cotton growers commonly use glufosinate-based programs to control glyphosate-resistant Palmer amaranth. Palmer amaranth must be small (≤7.5 cm) for consistent control by glufosinate, and growers often miss the optimum application timing. XtendFlex™ cotton may provide growers a tool to control larger Palmer amaranth. Glufosinate, dicamba, and glufosinate plus dicamba were compared for Palmer amaranth control in a rescue situation. Herbicides were applied to 16- to 23-cm weeds (POST-1) followed by a second application (POST-2) 12 d later. Glufosinate-ammonium at 590 g ai ha−1 plus dicamba diglycolamine salt at 560 g ae ha−1 POST-1 followed by glufosinate plus dicamba POST-2 was more effective than glufosinate at 880 g ha−1 POST-1 followed by glufosinate at 590 g ha−1 POST-2 or dicamba alone applied twice. Following a directed layby application of glyphosate, diuron, and S-metolachlor 14 d after POST-2, Palmer amaranth was controlled 99% by any system containing dicamba or glufosinate plus dicamba POST-1 followed by dicamba, glufosinate, or glufosinate plus dicamba POST-2 compared with 87% to 91% control by glufosinate alone applied twice. Cotton height and number of main stem nodes at layby were reduced in systems with dicamba only POST-1 followed by dicamba or glufosinate plus dicamba POST-2, presumably due to competition from the slowly dying Palmer amaranth with dicamba only POST-1. These treatments also delayed cotton maturity and reduced lint yield compared with systems containing glufosinate plus dicamba at POST-1.
Effect of Delayed Dicamba plus Glufosinate Application on Palmer Amaranth (Amaranthus palmeri) Control and XtendFlex™ Cotton Yield
- Rachel A. Vann, Alan C. York, Charles W. Cahoon, Jr., Trace B. Buck, Matthew C. Askew, Richard W. Seagroves
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- Journal:
- Weed Technology / Volume 31 / Issue 5 / October 2017
- Published online by Cambridge University Press:
- 06 September 2017, pp. 633-640
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Glufosinate controls glyphosate-resistant Palmer amaranth, but growers struggle to make timely applications. XtendFlexTM cotton, resistant to dicamba, glufosinate, and glyphosate, may provide growers an option to control larger weeds. Palmer amaranth control and cotton growth, yield, and fiber quality were evaluated in a rescue situation created by delaying the first POST herbicide application. Treatments consisted of two POST applications of dicamba plus glufosinate, separated by 14 d, with the first application timely (0-d delay) or delayed 7, 14, 21, or 28 d. All treatments included a layby application of diuron plus MSMA. Palmer amaranth, 14 d after first POST, was controlled 99, 96, 89, 75, and 73% with 0-, 7-, 14-, 21-, or 28-d delays, respectively. Control increased following the second application, and the weed was controlled at least 94% following layby. Cotton yield decreased linearly as first POST application was delayed, with yield reductions ranging from 8 to 42% with 7- to 28-d delays. Delays in first POST application delayed cotton maturity but did not affect fiber quality.
Contributors
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- By Aakash Agarwala, Linda S. Aglio, Rae M. Allain, Paul D. Allen, Houman Amirfarzan, Yasodananda Kumar Areti, Amit Asopa, Edwin G. Avery, Patricia R. Bachiller, Angela M. Bader, Rana Badr, Sibinka Bajic, David J. Baker, Sheila R. Barnett, Rena Beckerly, Lorenzo Berra, Walter Bethune, Sascha S. Beutler, Tarun Bhalla, Edward A. Bittner, Jonathan D. Bloom, Alina V. Bodas, Lina M. Bolanos-Diaz, Ruma R. Bose, Jan Boublik, John P. Broadnax, Jason C. Brookman, Meredith R. Brooks, Roland Brusseau, Ethan O. Bryson, Linda A. Bulich, Kenji Butterfield, William R. Camann, Denise M. Chan, Theresa S. Chang, Jonathan E. Charnin, Mark Chrostowski, Fred Cobey, Adam B. Collins, Mercedes A. Concepcion, Christopher W. Connor, Bronwyn Cooper, Jeffrey B. Cooper, Martha Cordoba-Amorocho, Stephen B. Corn, Darin J. Correll, Gregory J. Crosby, Lisa J. Crossley, Deborah J. Culley, Tomas Cvrk, Michael N. D'Ambra, Michael Decker, Daniel F. Dedrick, Mark Dershwitz, Francis X. Dillon, Pradeep Dinakar, Alimorad G. Djalali, D. John Doyle, Lambertus Drop, Ian F. Dunn, Theodore E. Dushane, Sunil Eappen, Thomas Edrich, Jesse M. Ehrenfeld, Jason M. Erlich, Lucinda L. Everett, Elliott S. Farber, Khaldoun Faris, Eddy M. Feliz, Massimo Ferrigno, Richard S. Field, Michael G. Fitzsimons, Hugh L. Flanagan Jr., Vladimir Formanek, Amanda A. Fox, John A. Fox, Gyorgy Frendl, Tanja S. Frey, Samuel M. Galvagno Jr., Edward R. Garcia, Jonathan D. Gates, Cosmin Gauran, Brian J. Gelfand, Simon Gelman, Alexander C. Gerhart, Peter Gerner, Omid Ghalambor, Christopher J. Gilligan, Christian D. Gonzalez, Noah E. Gordon, William B. Gormley, Thomas J. Graetz, Wendy L. Gross, Amit Gupta, James P. Hardy, Seetharaman Hariharan, Miriam Harnett, Philip M. Hartigan, Joaquim M. Havens, Bishr Haydar, Stephen O. Heard, James L. Helstrom, David L. Hepner, McCallum R. Hoyt, Robert N. Jamison, Karinne Jervis, Stephanie B. Jones, Swaminathan Karthik, Richard M. Kaufman, Shubjeet Kaur, Lee A. Kearse Jr., John C. Keel, Scott D. Kelley, Albert H. Kim, Amy L. Kim, Grace Y. Kim, Robert J. Klickovich, Robert M. Knapp, Bhavani S. Kodali, Rahul Koka, Alina Lazar, Laura H. Leduc, Stanley Leeson, Lisa R. Leffert, Scott A. LeGrand, Patricio Leyton, J. Lance Lichtor, John Lin, Alvaro A. Macias, Karan Madan, Sohail K. Mahboobi, Devi Mahendran, Christine Mai, Sayeed Malek, S. Rao Mallampati, Thomas J. Mancuso, Ramon Martin, Matthew C. Martinez, J. A. Jeevendra Martyn, Kai Matthes, Tommaso Mauri, Mary Ellen McCann, Shannon S. McKenna, Dennis J. McNicholl, Abdel-Kader Mehio, Thor C. Milland, Tonya L. K. Miller, John D. Mitchell, K. Annette Mizuguchi, Naila Moghul, David R. Moss, Ross J. Musumeci, Naveen Nathan, Ju-Mei Ng, Liem C. Nguyen, Ervant Nishanian, Martina Nowak, Ala Nozari, Michael Nurok, Arti Ori, Rafael A. Ortega, Amy J. Ortman, David Oxman, Arvind Palanisamy, Carlo Pancaro, Lisbeth Lopez Pappas, Benjamin Parish, Samuel Park, Deborah S. Pederson, Beverly K. Philip, James H. Philip, Silvia Pivi, Stephen D. Pratt, Douglas E. Raines, Stephen L. Ratcliff, James P. Rathmell, J. Taylor Reed, Elizabeth M. Rickerson, Selwyn O. Rogers Jr., Thomas M. Romanelli, William H. Rosenblatt, Carl E. Rosow, Edgar L. Ross, J. Victor Ryckman, Mônica M. Sá Rêgo, Nicholas Sadovnikoff, Warren S. Sandberg, Annette Y. Schure, B. Scott Segal, Navil F. Sethna, Swapneel K. Shah, Shaheen F. Shaikh, Fred E. Shapiro, Torin D. Shear, Prem S. Shekar, Stanton K. Shernan, Naomi Shimizu, Douglas C. Shook, Kamal K. Sikka, Pankaj K. Sikka, David A. Silver, Jeffrey H. Silverstein, Emily A. Singer, Ken Solt, Spiro G. Spanakis, Wolfgang Steudel, Matthias Stopfkuchen-Evans, Michael P. Storey, Gary R. Strichartz, Balachundhar Subramaniam, Wariya Sukhupragarn, John Summers, Shine Sun, Eswar Sundar, Sugantha Sundar, Neelakantan Sunder, Faraz Syed, Usha B. Tedrow, Nelson L. Thaemert, George P. Topulos, Lawrence C. Tsen, Richard D. Urman, Charles A. Vacanti, Francis X. Vacanti, Joshua C. Vacanti, Assia Valovska, Ivan T. Valovski, Mary Ann Vann, Susan Vassallo, Anasuya Vasudevan, Kamen V. Vlassakov, Gian Paolo Volpato, Essi M. Vulli, J. Matthias Walz, Jingping Wang, James F. Watkins, Maxwell Weinmann, Sharon L. Wetherall, Mallory Williams, Sarah H. Wiser, Zhiling Xiong, Warren M. Zapol, Jie Zhou
- Edited by Charles Vacanti, Scott Segal, Pankaj Sikka, Richard Urman
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- Book:
- Essential Clinical Anesthesia
- Published online:
- 05 January 2012
- Print publication:
- 11 July 2011, pp xv-xxviii
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