Source: NORTH CAROLINA STATE UNIV submitted to NRP
MANAGING HERBICIDE-RESISTANT WEEDS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0225786
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2011
Project End Date
Sep 30, 2016
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
Crop Science
Non Technical Summary
Cotton and wheat return $257 and $89 million, respectively, to NC growers. Weeds cost growers $30 million and $16 million annually in cotton and wheat, respectively. Italian ryegrass is the most troublesome weed in wheat in NC. It is very competitive with wheat, causes lodging, interferes with harvesting, and contaminates harvested grain. Dense populations of this weed are common, and wheat yield reductions of 50% or greater are common in uncontrolled populations. Presence of ryegrass seed also can lead to a substantial price dockage. Diclofop, an ACCase inhibitor, was widely used by wheat growers to effectively control Italian ryegrass for many years. Excessive reliance on diclofop led to selection of resistant biotypes. Mesosulfuron, an ALS inhibitor, has been widely used to control ryegrass since 2005. It was initially very effective, but growers are reporting control failures, and resistance is suspected. The problems are primarily in areas where diclofop resistance is known to occur, hence raising the possibility of multiple resistance. Research is needed to confirm resistance, determine if cross resistance to other ALS inhibitors occurs, and to determine if multiple resistance to ALS and ACCase inhibitors is present. Work is also needed to determine the distribution of resistance in the state. Additionally, growers need alternative management strategies for this problem weeds. The proposed research is expected to lead to effective management options for resistant ryegrass. Glyphosate resistance is also suspected in Italian ryegrass in parts of NC. This has the potential to become a very serious problem, as the weed is commonly found in the predominant no-till region of the state. Effective burndown before planting is necessary to avoid competition and yield reduction. Research is need to confirm resistance and to determine if these biotypes are resistant to other modes of action; this information will help direct educational programs. Research is needed to develop alternative burndown programs that are compatible with local farming practices. The proposed research should lead to effective alternatives for ryegrass burndwon in no-till, thus allowing growers to continue no-till planting. Glyphosate-resistant Palmer amaranth was first found in NC in 2005. The resistant biotype is now widespread across the Coastal Plain and is suspected to be present in the Piedmont region. With essentially all the cotton being Roundup Ready, this weed has caused major problems for growers. Growers are spending an additional $30 to $50 per acre for herbicides, and many growers are also hand-weeding at an average cost $30 per acre. Inspite of this, the weed is still causing significant yield losses. Research must be ocntinued to refine management strategies using current technology to better control the weed and reduce losses. New technology, both herbicides and herbicide-resistant cotton, is being developed. Research is needed to determine how best to use the new technology so that educational programs can be developed that advise growers on how to use the new technology in a sustainable and cost-effective manner.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2131542114020%
2131710114080%
Knowledge Area
213 - Weeds Affecting Plants;

Subject Of Investigation
1542 - Soft red wheat; 1710 - Upland cotton;

Field Of Science
1140 - Weed science;
Goals / Objectives
A. ALS-resistant Italian ryegrass: 1. Confirm resistance to mesosulfuron in NC biotypes of Italian ryegrass 2. Determine extent of cross resistance in NC Italian ryegrass to ALS-inhibiting herbicides commonly used in wheat 3. Determine if ALS-resistant biotypes of Italian ryegrass in NC have multiple resistance to commonly used wheat herbicides with other modes of action 4. Develop management systems for ALS-resistant Italian ryegrass in wheat,focusing on pyroxasulfone, S-3530, flumioxazin, and pinoxaden as alternatives to mesosulfuron and pyroxsulam B. Glyphosate-resistant Italian ryegrass 1. Determine distribution of glyphosate-resistant Italian ryegrass in NC 2. Determine level of glyphosate resistance in NC Italian ryegrass populations 3. Determine if glyphosate-resistant biotypes of Italian ryegrass in NC have multiple resistance to other modes of action 4. Develop effective management options for glyphosate-resistant Italian ryegrass, with emphases on burndown programs C. Glyphosate-resistant Palmer amaranth 1. Refine management systems for glyphosate-resistant Palmer amaranth in cotton using currently available technology a. Evaluate alternatives to two PPO inhibitors applied preplant and preemergence in no-till cotton b. Evaluate crop response and Palmer amaranth control with pyroxasulfone and an encapsulated acetochlor formulation to s-metolachlor c. Determine cotton response to acetochlor as affected by co-application with insecticides and pyrithiobac d. Determine response of cotton with the Widestriker trait to multiple applications and timings of application of glufosinate e. Compare Palmer amaranth control and economic returns in the best performing cultivars with a complete herbicide program utilizing glufosinate-based programs applied to cultivars with the LibertyLinkr trait,glufosinate- and glyphosate-based programs in a cultivar with both the Widestriker and Roundup Readyr Flex traits, and glyphosate-based programs in a variety with only the Roundup Readyr Flex trait. 2. Evaluate Palmer amaranth control in new transgenic cottons a. Determine response of Palmer amaranth to mixtures of glufosinate plus 2,4-D, glufosinate plus dicamba, glyphosate plus 2,4-D, and glyphosate plus dicamba as affected by herbicide rate and weed size b. Determine control of multiple weed species with mixtures and sequential applications of glyphosate and glufosinate, with emphases on rates in mixtures, order of sequential applications, and time intervals between herbicides in sequential applications c. Develop management systems utilizing DHT and DGT/RR cotton
Project Methods
Experiments will be conducted on research stations and private farms using traditional small-plot research techniques. Greenhouse studies will be conducted to determine resistance in ryegrass populations and to follow up on observations in the field. Ryegrass seed will be collected from multiple areas where resistance to mesosulfuron is suspected. In a greenhouse, seedlings will be treated with varying rates of ACCase inhibitors and ALS inhibitors to determine I50 values for visible control and fresh weight reduction. Field experiments will be conducted in wheat fields naturally infested with Italian ryegrass to evaluate control and crop response with various herbicide systems, including currently available and experimental herbicides. Italian ryegrass seed have been collected from areas with suspected glyphosate resistance. Greenhouse trials will determine if these populations are resistant to glyphosate and determine if multiple resistance to various ALS and ACCase inhibitors is present. Field experiments will be conducted to find alternatives to glyphosate for burndown ahead of no-till crops. Seed will be collected from multiple locations across the state to determine the distribution of glyphosate resistance. To determine distribution of glyphosate-resistant Palmer amaranth, the state will be intensively grid sampled. Seed will be screened for resistance to glyphosate, glufosinate, ALS inhibitors, and PPO inhibitors. A number of field experiments will be conducted to evaluate management systems for Palmer amaranth in cotton, including but not limited to the following: a. Compare Palmer amaranth control in no-till cotton with two PPO inhibitors (flumioxazin preplant and fomesafen preemergence) versus one PPO inhibitor (flumioxazin preplant with diuron preemergence, and diuron preplant with fomesafen preemergence); b. Evaluate cotton response to encapsulated acetochlor and pyroxasulfone versus s-metolachlor, focusing on cotton growth state, numbers of applications, and mixtures with other pesticides; c. Determine response of Widestrike cotton to glufosinate as affected by number and time of application, with emphases on later applications; d. Compare Palmer amaranth control, crop response, and net returns with recommended management systems utilizing glyphosate in a Roundup Ready Flex variety and a Widestrike/Roundup Ready Flex variety, and systems utilizing glufosinate in a LibertyLink variety and a Widestrike variety; e. Determine control of Palmer amaranth and other species with tank-mix and sequential applications of various combinations of dicamba, 2,4-D, glufosinate, and glyphosate.

Progress 10/01/11 to 09/30/16

Outputs
Target Audience:Target audience is crop producers in North Carolina and those who advise producers, such as extension agents, consultants, and agrichemical dealers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Research programs for three graduate students were based entirely on the above reported work, while an additional three graduate students were involved in some of thework and were able to get some publications plus acquire experience in presenting results at professional meetings. How have the results been disseminated to communities of interest?In addition to the publications in refereed journals for professional audiences, the data generated has been incorporated into educational programs for growers, consultants, and agrichemical dealers. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Herbicide-resistant (HR) weeds have become a major impediment to profitable crop production. Research under this project has helped the scientific community better understand the biology of HR weeds and how to better manage them. Results have been incorporated into educational programs and recommendations for growers and those who advise growers. Growers have widely adopted systems developed through the research and are effectively managing HR weeds, thus reducing yield losses and increasing profitability. 1. ALS-resistant Italian ryegrass: At beginning of current project, research was in final stages to confirm ALS resistance in NC populations. Cross resistance to ALS inhibitors mesosulfuron, pyroxsulam, and imazamox was confirmed as was cross resistance with diclofop and pinoxaden in some populations. A number of populations exhibited multiple resistance to ACCase and ALS inhibitors. Research was conducted using flumioxazin and pyroxasulfone as alternatives to ALS inhibitors. In no-till wheat, flumioxazin was safe to the crop if applied 7 or more days ahead of planting. Ryegrass control was relatively good but flumioxazin was not a stand-alone treatment; a follow-up postemergence (POST) herbicide was typically needed. Pyroxasulfone was effective and safe on wheat applied preemergence (PRE) on clay soils, but injury was observed on sandy soils. Tolerance was good when applied POST to wheat in the spike stage or later. 2. Glyphosate-resistant Italian ryegrass: Seed from a segregating population suspected of being resistant to glyphosate was used as a plant source for both GR (glyphosate-resistant) and GS (glyphosate-susceptible) biotypes to compare the following: shikimate production and level of resistance; early season interference with wheat; effect of drought stress; and response to POST herbicides. A 3.2-fold level of resistance was confirmed. Shikimate production in both biotypes increased as glyphosate rate increased; differences between biotypes were noted only at lower rates of glyphosate. Interference with crop growth did not differ between biotypes. Ryegrass response to drought stress did not differ by biotype. Control by various herbicides other than glyphosate was similar across biotypes. In field trials, paraquat followed by (fb) paraquat or paraquat plus atrazine and clethodim fb paraquat plus atrazine were highly effective. No single application was adequately effective. Evaluation of nozzles and spray volumes indicated better control with higher spray volumes and smaller droplets. 3. Glyphosate-resistant Palmer amaranth: Palmer amaranth (AMAPA) is the most troublesome weed in NC row crops. A survey in fall of 2010, with screening during this project's time frame, revealed 98 and 97% of populations were resistant to glyphosate and ALS inhibitors, respectively, and 95% of populations expressed multiple resistance to both herbicides. Several studies examined biology and physiology of GR biotypes. Trials focused on competitiveness of GR and GS biotypes, response to drought stress, and response to herbicides other than glyphosate indicated that in absence of selection pressure, glyphosate resistance does not influence growth and competitiveness of biotypes. Both accumulated shikimate following glyphosate application, with greater concentrations in GS biotypes. Greater glyphosate absorption was noted 6 h after treatment (HAT) in the GS biotype, but no differences were observed 12 to 72 HAT. Results suggest resistance is not due to an altered target enzyme or translocation but may be in part due to rate of glyphosate absorption. Results are consistent with resistance being due to increased gene copy number for the target enzyme. Inheritance studies indicated resistance is incompletely dominant, nuclear-inherited, and not consistent with a single gene mechanism of inheritance. Variable EPSPS gene copy number in parents suggested copy number could be influential in determining if inheritance of resistance is monogenic or polygenic. With GR AMAPA being widespread, residual herbicides are strongly recommended PRE and POST. Cotton growers are depending more on glufosinate. In 2017, varieties and herbicides were first available for XtendFlex cotton, tolerant of dicamba, glyphosate, and glufosinate. A number of studies, many published, evaluated management programs for AMAPA in cotton. The following were pertinent results: a. Microencapsulated acetochlor applied PRE, especially mixed with fomesafen, effectively controlled AMAPA with minimal cotton injury. b. Pyroxasulfone PRE controlled AMAPA similar to acetochlor but caused unacceptable crop injury. Pyroxasulfone POST, mixed with glyphosate, controlled AMAPA as well as metolachlor or acetochlor but crop injury was unacceptable. c. Pyrithiobac mixed with glufosinate plus a chloroacetamide herbicide enhanced AMAPA control while giving injury similar to glufosinate plus a chloroacetamide. d. Fluridone PRE controlled AMAPA equal to or greater than acetochlor, diuron, fomesafen, or pendimethalin. e. Fluridone at 280 to 1120 g ai/ha, rates well above typical use rates, did not injure cotton and caused only minor injury but no yield loss to a subsequent crop of corn, peanut, grain sorghum, or soybean f. There is increasing concern over selection for PPO inhibitor resistance because of widespread use in a number of crops commonly grown in rotation. Flumioxazin, a PPO inhibitor, preplant was more effective than diuron preplant. Fomesafen, a PPO inhibitor, applied PRE was more effective than diuron. However, programs with flumioxazin preplant fb diuron PRE were as effective as flumioxazin preplant fb fomesafen PRE. Fluridone and flumioxazin applied preplant were similarly effective. Fluridone and acetochlor plus diuron applied PRE controlled Palmer amaranth as well as fomesafen plus diuron PRE. g. Fluometuron mixed with glufosinate increased injury but did not affect yield. Fluometuron did not increase control of 13-cm AMAPA but did increase control of 26-cm AMAPA. Delaying application until AMAPA was 26 cm reduced yield 22% relative to timely application. h. Co-application of glufosinate plus glyphosate was more effective on AMAPA than glyphosate alone but never more effective than glufosinate alone. Glufosinate and glyphosate co-applied were less effective than glyphosate alone on annual grasses, but not less effective than glufosinate alone. Glufosinate followed by (fb) glyphosate was the preferred order for sequential application to control AMAPA. j. AMAPA control by mixtures of glufosinate or glyphosate plus 2,4-D or dicamba exceeded control by respective herbicides alone. 2,4-D reduced annual grass control by glufosinate. k. AMAPA control in dicamba-based systems exceeded control in non-dicamba glyphosate-based systems but not non-dicamba glufosinate-based systems. l. In trials looking at rescue control of AMAPA by dicamba/glufosinate applications, delaying initial application for 1 to 4 weeks caused a linear decrease in cotton yield. However, two dicamba/glufosinate applications controlled large AMAMA, even when the initial application was delayed 4 weeks. m. In a 4-year study on AMAPA population dynamics, dicamba included with glyphosate reduced the AMAPA seedbank and the frequency of glyphosate resistance. n. In a 4-year study of continuous cotton, a single deep tillage operation in year 1 decreased AMAPA populations 75% the following year. Hand removal of AMAPA prior to seed production each year decreased AMAPA density and the frequency of glyphosate resistance after 4 years. However, after 4 seasons, cumulative economic return was not affected by deep tillage or hand-removal.

Publications

  • Type: Journal Articles Status: Published Year Published: 2012 Citation: Chandi, A., S.R. Milla-Lewis, D. Giacomini, P. Westra, C. Preston, D.L. Jordan, A.C. York, J.D. Burton, and J.R. Whitaker. 2012. Inheritance of evolved glyphosate resistance in a North Carolina Palmer amaranth (Amaranthus palmeri) biotype. Online. Int. J. Agron., Vol. 2012, Article ID 176108, 7 pages. doi:10.1155/2012/176108.
  • Type: Journal Articles Status: Published Year Published: 2012 Citation: Chandi, A., D.L. Jordan, A.C. York, S.R. Milla-Lewis, J.D. Burton, A.S. Culpepper, and J.R. Whitaker. 2012. Interference of selected Palmer amaranth (Amaranthus palmeri) biotypes in soybean (Glycine max). Online. Int. J. Agron.. Vol. 2012, Article ID 168267, 7 pages, 2012. doi:10.1155/2012/168267.
  • Type: Journal Articles Status: Published Year Published: 2012 Citation: Hoffner, A.E., D.L. Jordan, A.C. York, E.J. Dunphy, and W.J. Everman. 2012. Influence of soybean (Glycine max) population and herbicide program on Palmer amaranth (Amaranthus palmeri) control, soybean yield, and economic return. Online. ISRN Agron, Vol. 2012, Article ID 947395, 8 pages, 2012. doi:10.5402/2012/947395.
  • Type: Journal Articles Status: Published Year Published: 2012 Citation: Hoffner, A., D.L. Jordan, A. Chandi, A. C. York, E.J. Dunphy, and W.E. Everman. 2012. Management of Palmer amaranth (Amaranthus palmeri) in glufosinate-resistant soybean (Glycine max) with sequential applications of herbicides. Online. ISRN Agron,Vol. 2012, Article ID 131650, 7 pages, 2012. doi:10.5402/2012/131650.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Barnett, K. A., A. S. Culpepper, A. C. York, and L. E. Steckel. 2013. Palmer amaranth (Amaranthus palmeri) control by glufosinate plus fluometuron applied postemergence to WideStrike� cotton. Weed Technol. 27:291-297.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Chandi, A., D.L. Jordan, A. York, S. Milla-Lewis, J. Burton, S. Culpepper, and J. Whitaker. 2013. Interference and control of glyphosate-resistant and susceptible Palmer amaranth (Amaranthus palmeri) populations under greenhouse conditions. Weed Sci. 61:259-266.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Chandi, A., D. L. Jordan, S. Milla-Lewis, A. York, J. Burton, C. Zuleta, J. Whitaker, and S. Culpepper. 2013. Use of AFLP markers to assess genetic diversity in Palmer amaranth (Amaranthus palmeri) populations from North Carolina and Georgia. Weed Sci. 61:136-145.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Chandi, A., D.L. Jordan, A. C. York, J. Burton, S.R Milla-Lewis, J. Spears, J.R. Whitaker, and R. Wells. 2013. Response of herbicide-resistant Palmer amaranth (Amaranthus palmeri) accessions to drought stress. Int. J. Agron. Volume 2013, Article ID 823913, 8 pages. http://dx.doi.org/10.1155/2013/823913.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Merchant, R.M., L.M. Sosnoskie, A.S. Culpepper, L.E. Steckel, A.C. York, L.B. Braxton, and J.C. Ford. 2013. Weed response to 2,4-D, 2,4-DB, and dicamba applied alone or with glufosinate. J. Cotton Sci. 17:212218.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Whitaker, J.R., J.D. Burton, A.C. York, D.L. Jordan, and A. Chandi. 2013. Physiology of glyphosate-resistant and glyphosate-susceptible Palmer amaranth (Amaranthus palmeri) biotypes collected from North Carolina. Int. J. Agron. Volume 2013, Article ID 429294, 6 pages. http://dx.doi.org/10.1155/2013/429294
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, W.J. Everman, and R.W. Seagroves. 2014. An alternative to multiple protoporphyrinogen oxidase inhibitor applications in no-till cotton. Weed Technol. 28:58-71.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Jordan, D., A. York, R. Seagroves, W. Everman, B. Clewis, J. Wilcut, D. Shaw, M. Owen, R. Wilson, B. Young, and S. Weller. 2014. Economic value of herbicide programs and implications for resistance management in North Carolina. J. Crop Manag. DOI:10.2134/CM-2014-0023-RS. 6 pages.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Poirier, A.H., A.C. York, D.L. Jordan, A. Chandi, W.J. Everman, and J.R. Whitaker. 2014. Distribution of Glyphosate- and Thifensulfuron-Resistant Palmer Amaranth (Amaranthus palmeri) in North Carolina," International Journal of Agronomy, vol. 2014, Article ID 747810, 7 pages, 2014. doi:10.1155/2014/747810.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Braswell, L.R., A.C. York, D.L. Jordan, and R.W. Seagroves. 2015. Effect of diuron and fluometuron on grain sorghum and soybean as replacement crops following a cotton stand failure. J. Cotton Sci. 19:613-621.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, W.J. Everman, R.W. Seagroves, L.R. Braswell, and K.M. Jennings. 2015. Weed control in cotton by combinations of microencapsulated acetochlor and various residual herbicides applied preemergence. Weed Technol. 29:740-750.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, W.J. Everman, R.W. Seagroves, A.S. Culpepper, and P.M. Eure. 2015. Palmer amaranth (Amaranthus palmeri) management in dicamba-resistant cotton. Weed Technol. 29: 758-770.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, and R.W. Seagroves. 2015. Cotton response and Palmer amaranth control with mixtures of glufosinate and residual herbicides. J. Cotton Sci. 19:622-630.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, R.W. Seagroves, W.J. Everman, and K.M. Jennings. 2015. Cotton response and Palmer amaranth control with pyroxasulfone applied preemergence and postemergence. J. Cotton Sci. 19:212-223.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, R.W. Seagroves, W.J. Everman, and K.M. Jennings. 2015. Sequential and co-application of glyphosate and glufosinate in cotton. J. Cotton Sci. 19:337-350.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, R.W. Seagroves, W.J. Everman, and K.M. Jennings. 2015. Fluridone carryover to rotational crops following application to cotton. J. Cotton Sci. 19:631-640.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Braswell, L. R., W. W. Cahoon, R. W. Seagroves, D. L. Jordan, and A. C. York, 2016. Integrating fluridone into a glufosinate-based program for Palmer amaranth control in cotton. J. Cotton Sci. 20:394-402.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Braswell, L.R., C.W. Cahoon, A.C. York, D.L. Jordan, and R.W. Seagroves. 2016. Fluridone and encapsulated acetochlor reduce protoporphyrinogen oxidase inhibitor use in a glufosinate-based Palmer amaranth management program for cotton. Weed Technol. 30:838-847.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Inman, M.D., D.L. Jordan, A.C. York, K.M. Jennings, D.W. Monks, W.J. Everman, S.L. Bollman, J.T. Fowler, R.M. Cole, and J.K. Soteres. 2016. Long-term management of Palmer amaranth (Amaranthus palmeri) in dicamba-tolerant cotton. Weed Sci. 64:161-169.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Chaudhari, S., D.L. Jordan, A.C. York, K.M. Jennings, C.W. Cahoon, A. Chandi, and M.D. Inman. 2017. Biology and management of glyphosate-resistant and -susceptible Palmer amaranth (Amaranthus palmeri) phenotypes from a segregating population. Weed Sci. 65:755-768.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Inman, M. D., D. L. Jordan, and A. C. York. 2017. Long-term management of Palmer amaranth with herbicides and cultural practices in cotton. Crop, Forage, and Turfgrass Management doi:10.2134/cftm2017.03.0017.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Vann, R.A., A.C. York, C.W. Cahoon Jr., T.B. Buck, M.C. Askew, and R.W. Seagroves. 2017. Effect of delayed dicamba plus glufosinate application on Palmer amaranth (Amaranthus palmeri) control and XtendFlexTM cotton yield. Weed Technol. 31:633-640.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Vann, R.A., A.C. York, C.W. Cahoon Jr., T.B. Buck, M.C. Askew, and R.W. Seagroves. 2017. Glufosinate plus dicamba for rescue Palmer amaranth control in XtendFlexTMcotton. Weed Technol. 31:666-674.
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Chaudhari, S., D.L. Jordan, A.C. York, K.M. Jennings, C.W. Cahoon, A. Chandi, and A. Brown. 2017. Biology and management of glyphosate-resistant and -susceptible Italian ryegrass (Lolium multiflorum) phenotypes from a segrating population. Weed Sci.


Progress 10/01/14 to 09/30/15

Outputs
Target Audience:Cotton growers and those who advise cotton growers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Research has been presented at professional meetings, at field days, and at grower educational meetings. Results has been incorporated into extension recommendations. What do you plan to do during the next reporting period to accomplish the goals?Will continue with experiments focused on improving Palmer amaranth control in cotton.

Impacts
What was accomplished under these goals? Work on ALS-resistant Italian ryegrass and glyphosate-resistant ryegrass was accomplished under previous reporting periods. Work in the current reporting period focused on glyphosate-resistant Palmer amaranth. Tolerance to 2,4-D in cotton with the Enlist trait and tolerance to dicamba in cotton with the XtendFlex trait was shown to be very good. Some cosmetic injury was noted with high rates but yield and maturity and fiber quality were unaffected. Management systems incorporating 2,4-D in Enlist cotton and dicamba in XtendFlex cotton controlled glyphosate-resistant Palmer amaranth very well. It was found that dicamba offers good "salvage" control of larger Palmer amaranth but the cotton suffered yield losses due to early season competition. A number of preemergence herbicides, included as components of an overall management system, were found to have value in managing Palmer amaranth. Fomesafen, acetochlor, and fluridone, and especially combinations, were most effective.

Publications

  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C. W., A. C. York, D. L. Jordan, R. W. Seagroves, W. J. Everman, and K. M. Jennings. 2015. Fluridone carryover to rotational crops following application to cotton. J. Cotton Sci. 19:631-640.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C. W., A. C. York, D. L. Jordan, R. W. Seagroves, W. J. Everman, and K. M. Jennings. 2015. Sequential and co-application of glyphosate and glufosinate in cotton. J. Cotton Sci. 19:337-350.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C. W., A. C. York, D. L. Jordan, and R. W. Seagroves. 2015. Cotton response and Palmer amaranth control with mixtures of glufosinate and residual herbicides. J. Cotton Sci. 19:622-630.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C. W., A. C. York, D. L. Jordan, W. J. Everman, R. W. Seagroves, A. S. Culpepper, and P. M. Eure. 2015. Palmer amaranth (Amaranthus palmeri) management in dicamba-resistant cotton. Weed Technol. 29:758-770.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Cahoon, C. W., A. C. York, D. L. Jordan, W. J. Everman, R. W. Seagroves, L. R. Braswell, and K. M. Jennings. 2015. Weed control in cotton by combinations of microencapsulated acetochlor and various residual herbicides applied preemergence. Weed Technol. 29:740-750.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Braswell, L. R., A. C. York, D. L. Jordan, and R. W. Seagroves. 2015. Effect of diuron and fluometuron on grain sorghum and soybean as replacement crops following a cotton stand failure. J. Cotton Sci. 19:613-621.
  • Type: Journal Articles Status: Accepted Year Published: 2016 Citation: Inman, M., D. L. Jordan, A. York, K. Jennings, D. Monks, W. Everman, S. Bollman, J. Fowler, R. Cole, and J. Soteres. 2016. Long-term management of Palmer amaranth in dicamba-tolerant cotton. Weed Sci. 64: (in press).


Progress 10/01/13 to 09/30/14

Outputs
Target Audience: Cotton growers and those who advise cotton growers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Research has been presented at professional meetings, at field days, and at grower educational meetings. Research has been incorporated into extension publications and recommendations. What do you plan to do during the next reporting period to accomplish the goals? Will continue much the same.

Impacts
What was accomplished under these goals? Forty research trials conducted focusing on managing glyphosate-resistant Palmer amaranth in cotton. Determined that fluridone effectively controlled the weed and that it could substitute for one PPO-inhibitor application. Determined that fluridone at projected use rates does not carry over to sorghum or soybean rotational crops. Determined that encapsulated acetochlor could be safely used preemergence in cotton and that it allowed reduced rates of fomesafen without sacrificing control. Determined that grain sorghum could be planted 3 weeks after failed stand of cotton which had received diuron or fluometuron. Soybean required 6 weeks between diuron or fluometuron application and planting. Tillage generally enhanced soybean injury when planted following diuron or fluometuron. Determined that terbufos applied in-furrow did not interact with commonly used cotton herbicides. Determined tolerance of Enlist and Xtend cotton to 2,4-D and dicamba, respectively, when applied alone and in mixtures with other herbicides at various rates and timings of application. Determined excellent Palmer amaranth control in management systems utilizing Enlist and Xtend technologies.

Publications

  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Cahoon, C.W., A.C. York, D.L. Jordan, W.J. Everman, and R.W. Seagroves. 2014. An alternative to multiple protoporphyrinogen oxidase inhibitor applications in no-till cotton. Weed Technol. 28:58-71.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Poirier*, A. H., A. C. York, D. L. Jordan, A. Chandi, W. J. Everman, and J. R. Whitaker. 2014. Distribution of glyphosate- and thifensulfuron-resistant Palmer amaranth (Amaranthus palmeri) in North Carolina. Int. J. Agron., Vol. 2014, Article ID 747810, 7 p. http://www.hindawi.com/journals/ija/2014/747810.
  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: Barnett, K. A., A. S. Culpepper, A. C. York, and L. E. Steckel. Widestrike� cotton response to repeated applications of glufosinate at various application timings. Weed Technol. (accepted).
  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: Cahoon, C. W., A. C. York, D. L. Jordan, R. W. Seagroves, W. J. Everman, and K. M. Jennings. Cotton response and Palmer amaranth control with pyroxasulfone applied preemergence and postemergence. J. Cotton Sci. (accepted).


Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Target audience is cotton growers of North Carolina and those who advise growers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Training programs for growers, extension agents, dealers, and consultants were conducted. What do you plan to do during the next reporting period to accomplish the goals? Research will continue to build upon previous findings in order to develop more effective and sustainable management systems for herbicide-resistant weeds.

Impacts
What was accomplished under these goals? Thirty research trials conducted focusing on managing glyphosate-resistant Palmer amaranth in cotton. Determined that use of PPO inhibitors can be reduced without sacrificing control. Determined that pyroxasulfone controlled Palmer amaranth well but was too injurious for use on cotton. Encapsulated acetochlor was found to be effective on Palmer amaranth and safe on cotton. Applied POST, encapsulated acetochlor and s-metolachlor were similarly efficacious. Glufosinate, commonly applied to cotton with the Widestrike trait, was found to reduce yield of the most commonly planted variety.Excellent weed control and crop tolerance was found in experimental cotton lines with Enlist and Xtend traits.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Barnett, K.A., A.S. Culpepper, A.C. York, and L.E. Steckel. 2013. Palmer amaranth (Amaranthus palmeri) control by glufosinate plus fluometuron applied postemergence to WideStrike� cotton. Weed Technol. 27:291-297. Cahoon, C.W., A.C. York, D.L. Jordan, W.J. Everman, and R.W. Seagroves. 2013. An alternative to multiple protoporphyrinogen oxidase inhibitor applications in no-till cotton. Weed Technol. (in press). Accepted 8-23-2013. Ahead of print article available at http://www.wssajournals.org/doi/abs/10.1614/WT-D-13-00078.1. Chandi, A., D.L. Jordan, A. C. York, J. Burton, S.R Milla-Lewis, J. Spears, J.R. Whitaker, and R. Wells. 2013. Response of herbicide-resistant Palmer amaranth (Amaranthus palmeri) accessions to drought stress. Int. J. Agron. Volume 2013, Article ID 823913, 8 pages. http://dx.doi.org/10.1155/2013/823913. Chandi, A., S.R. Milla-Lewis, D.L. Jordan, A.C. York, J.D. Burton, M.C. Zuleta, J.R. Whitaker, and A. S. Culpepper. 2013. Use of AFLP markers to assess genetic diversity in Palmer amaranth (Amaranthus palmeri) populations from North Carolina and Georgia. Weed Sci. 61:136-145. Eure, P.M., D.L. Jordan, L.R. Fisher, and A.C. York. 2013. Efficacy of herbicides when spray solution application is delayed. Int. J. Agron. Volume 2013, Article ID 782486, 7 pages. http://dx.doi.org/10.1155/2013/782486 Merchant, R.M., L.M. Sosnoskie, A.S. Culpepper, L.E. Steckel, A.C. York, L.B. Braxton, and J.C. Ford. 2013. Weed response to 2,4-D, 2,4-DB, and dicamba applied alone or with glufosinate. J. Cotton Sci. 17:212218. Whitaker, J.R., J.D. Burton, A.C. York, D.L. Jordan, and A. Chandi. 2013. Physiology of glyphosate-resistant and glyphosate-susceptible Palmer amaranth (Amaranthus palmeri) biotypes collected from North Carolina. Int. J. Agron. Volume 2013, Article ID 429294, 6 pages. http://dx.doi.org/10.1155/2013/429294


Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: A number of trials were conducted during the period to determine the effect of various management systems and biological factors on management of herbicide-resistant weeds. Resistance to ALS-inhibiting herbicides was confirmed in common ragweed. Herbicides with different modes of action, including atrazine, dicamba, and glyphosate in corn; fomesafen, glyphosate, MSMA, and prometryn in cotton; bentazon, flumioxazin, and lactofen in peanut; and flumioxazin, glyphosate, and lactofen in soybean controlled the resistant ragweed more effectively than systems relying on ALS inhibitors in peanut, soybean corn, and cotton. Tank-mixes or sequential applications of herbicides with differing modes of action were effective in controlling ALS-resistant ragweed in all the crops. Glyphosate-resistant Palmer amaranth at 0.37 plants per square meter reduced soybean yield 21%. Glyphosate-resistant and -susceptible biotypes of Palmer amaranth responded similarly to glufosinate, lactofen, paraquat, and trifloxysulfuron whereas atrazine and dicamba were somewhat more effective on the resistant biotype. Under greenhouse conditions, there was a small competitive disadvantage for the resistant biotype. Increasing soybean plant population increased Palmer amaranth control. Systems of PRE and POST herbicides increased yield and net return in soybean compared with POST only systems. There is concern among weed scientists that we may select for PPO-resistant Palmer amaranth due to our extensive use of PPO inhibitors in multiple crops. Research in no-till cotton, where use of two PPO's preplant and PRE is common, showed that Palmer amaranth could be controlled well with flumioxazin preplant followed by diuron PRE, thus eliminating one PPO inhibitor. Glufosinate is being widely used in cotton to manage glyphosate-resistant Palmer amaranth. Research showed that time of day of application greatly impacted control. Poor control was achieved with glufosinate applied sooner than 2 hours after sunrise or later than 1 hour after sunset. Acetochlor is commonly applied POST in cotton in combination with glyphosate or glufosinate to gain extended residual control of Palmer amaranth. Cotton injury with that application is sometimes a concern. Research showed that acetochlor could be safely applied PRE to cotton without sacrificing weed control. In large-plot cotton variety/technology trials, it was found that recently released glufosinate- and glufosinate plus glyphosate-resistant varieties performed as well as glyphosate-resistant varieties. Application of glufosinate to PHY 499WRF cotton, a common practice, reduced yield. In addition to presentations at professional meetings and publication in professional journals, the results of these trials have been incorporated into educational programs and recommendations for row crop producers in North Carolina. PARTICIPANTS: Many of the trials under this project were conducted cooperatively with weed scientists in Georgia and Tennessee. This research was utilized for in-field and classroom training of extension agents and various agribusiness groups. Much of the work was done as part of graduate programs for three students. TARGET AUDIENCES: Target audiences were growers, extension agents, and agribusiness personnel. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Two primary goals of the project are to 1) determine how to better manage herbicide-resistant weeds and avoid selection for resistance, and 2) to disseminate the information to growers so they can better manage such weeds. As a result of educational programs developed from this research, all growers are now aware of the problem of herbicide resistance and most growers are following recommended practices for resistance management. As a result, most growers have decreased crop losses due to uncontrolled resistant weeds.

Publications

  • Chandi, A., D.L. Jordan, A.C. York, and B.R. Lassiter. 2012. Confirmation and management of common ragweed (Ambrosia artemisiifolia) resistant to diclosulam. Weed Technol. 26:29-36.
  • Chandi, A., D.L. Jordan, A. York, S. Milla-Lewis, J. Burton, S. Culpepper, and J. Whitaker. 2013. Interference and control of glyphosate-resistant and -susceptible Palmer amaranth (Amaranthus palmeri) populations under greenhouse conditions. Weed Sci. 61:(in press; accepted 10/26/2012).
  • Chandi, A., D.L. Jordan, A.C. York, S.R. Milla-Lewis, J.D. Burton, A.S. Culpepper, and J.R. Whitaker. 2012. Interference of selected Palmer amaranth (Amaranthus palmeri) biotypes in soybean (Glycine max). Online. Int. J. Agron.. Vol. 2012, Article ID 168267, 7 pages, 2012. doi:10.1155/2012/168267.
  • Hoffner, A.E., D.L. Jordan, A.C. York, E.J. Dunphy, and W.J. Everman. 2012. Influence of soybean (Glycine max) population and herbicide program on Palmer amaranth (Amaranthus palmeri) control, soybean yield, and economic return. Online. ISRN Agron, Vol. 2012, Article ID 947395, 8 pages, 2012. doi:10.5402/2012/947395.
  • Johnson, V.A., L.R. Fisher, D.L. Jordan, K.E. Edmisten, A.M. Stewart, and A.C. York. 2012. Cotton, peanut, and soybean response to sublethal rates of dicamba, glufosinate, and 2,4-D. Weed Technol. 26:195-206.
  • Main, C.L, J.C. Faircloth, L.E. Steckel, A.S. Culpepper, and A.C. York. 2012. Cotton tolerance to fomesafen applied preemergence. J. Cotton Sci. 16:80-87.