EVALUATION OF WEED MANAGEMENT STRATEGIES IN LOUISIANA RED RIVER VALLEY CORN AND SOYBEAN

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1016167
• Project Start Date: Jun 1, 2018
• Project End Date: Apr 30, 2022
• Program Code: [(N/A)]- (N/A)

Recipient Organization
LOUISIANA STATE UNIVERSITY
202 HIMES HALL
BATON ROUGE,LA 70803-0100

Performing Department
Dean Lee Research Station

Non Technical Summary
Weeds are one of the primary pest that crop producers plan for in their operation. Profitability of crop producers is highly influenced by the immense number of plant species that can be weedy pest in the desirable crop. In corn and soybean, weed management strategies can range from cultural to chemical. Louisiana crop producers typically utilize chemical application and tillage for weed management. The extensive use of chemicals for weed management in Louisiana requires determination of herbicide efficacy on problematic weedy pest. Also, numerous herbicide-tolerant crop technologies are available for use in Louisiana and their value needs to be evaluated. Overall, weed infestations will limit crop yield and profitability. Research into and development of management strategies for weedy pest in Louisiana is essential for the long-term success of a farming operation.

Animal Health Component

75%

Research Effort Categories

Basic

25%

Applied

75%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
213	2300	1140	100%

Knowledge Area
213 - Weeds Affecting Plants;

Subject Of Investigation
2300 - Weeds;

Field Of Science
1140 - Weed science;

Keywords

corn

soybean

weed management

Goals / Objectives
The first objective is to evaluate herbicide and herbicide-tolerant crops for weed management and crop tolerance in field corn and soybean.Thesecond objective is todevelop weed management strategies for crops and cropping systems in the Louisiana Red River Valleyis a goal.

Project Methods
Objective 1Research will investigate herbicides, herbicide-tolerant crops, and weed management programs. Evaluation of efficacy, and crop safety of experimental or currently registered herbicides and herbicide-resistant crops will be conducted at LSU AgCenter research and extension centers and, if needed, on-farm research sites where a problem weed or weed spectrum is identified. Research will involve small- and large-plot techniques that will complement each other. Small-plot experiments typically include a plot size of 2 to 8 rows, (7.5-40 inch row spacing) wide by 30 to 40-feet long with 3 to 4 replications of treatments. For large-plot techniques, plot size will typically equal the width of planting or pesticide application equipment and be at least 200-feet in length with no less than three replications per treatment.Research will be designed using appropriate experimental designs that allow for proper statistical analysis to reveal treatment strengths and weaknesses. Typically, treatments will be arranged in a randomized complete block (RCB) experimental design. Factorial arrangement of treatments in a RCB experimental design will be utilized when comparing multiple herbicides, rates, or application timings. The use of a split-plot experimental design will be used if weed management systems, such as tillage versus no-tillage, along with herbicide treatments, are tested.Herbicides will be applied with tractor-mounted compressed air systems, CO2-pressurized backpack systems, or with on-farm equipment that will be examined and tested for accuracy. Visual weed control estimates of percent control and crop injury will be recorded at appropriate intervals after application on a scale of 0 to 100% (0 = no control or injury and 100 = complete control or crop death). Crop yield data will also be collected if needed to access the feasibility of the treatment. Crop and weed growth parameter data will be collected to access the value of a treatment where appropriate.Data will be analyzed using the proper method as specified by treatment and experimental design under the advisement of the Louisiana State University Department of Experimental Statistics. Where appropriate, data will be correlated and regression utilized to predict efficacy or simple analysis of variance will be utilized and means separated using an appropriate mean separation method. Results of these trials will be a primary source for weed control recommendations provided through the Louisiana Cooperative Extension Service for distribution to county agents, producers, consultants, and the agricultural industry. Additionally, data will be published in producer-oriented and scientific publications.Objective 2Research to evaluate and develop management strategies different from other regions of Louisiana is needed primarily due to the inherent soil pH and weed spectrum of the Louisiana Red River Valley. Weed management programs will investigate the value of residual herbicides with and without postemergence herbicide applications for control of problematic weeds. Research will also be conducted to determine the potential for herbicide persistence and subsequent effect on crops following grown in rotation. Therefore, weed management systems for corn and soybean will be investigated. Similar procedures listed to accomplish objective 1 will also be utilized for objective 2.For all objectives, cooperative research with scientist from the Universities of Arkansas, Georgia, and Tennessee as well as Mississippi State University and the USDA-ARS will be conducted to answer questions for clientele from a wide geographic area.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Target audiences for this project include crop producers and weed management professionals. 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?The results have been disseminated to communities of interest through oral and poster presentations at scientific conferences, field days, demonstrations, personal visits, newsletters, and through extension field agents. What do you plan to do during the next reporting period to accomplish the goals?Continue to evaluate older herbicide for new uses and recently released herbicides for management of weed species in Louisiana. Also, continued evaluation of new herbicide tolerant technologies in corn and soybean.

Impacts
What was accomplished under these goals? Objective and goal 1 and 2: Diverse herbicide-tolerant technologies are available in soybean and research was conducted to determine best weed management practices in the different technologies. In soybean tolerant to dicamba and glyphosate, control of barnyardgrass, glyphosate-resistant Palmer amaranth, and prickly sida and an increase in yield was achieved only when residual herbicides were applied preemergence. Control of barnyardgrass and glyphosate-resistant Palmer amaranth and soybean yield was increased in 2,4-D, glyphosate, and glufosinate tolerant soybean and in soybean that are tolerant to only glyphosate and glufosinate when residual herbicides applied preemergence and early-postemergence. Regardless of herbicide technology, entireleaf morningglory, hemp sesbania, sicklepod, prickly sida, and hophornbeam copperleaf control was greater than 90% following all treatments. Research was conducted to determine if herbicide treatments applied preemergence, postemergence, or preemergence followed by postemergence would provide acceptable weed control at corn harvest. Preliminary data indicated that a preemergence followed by postemergence application was needed.

Publications

• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Batts, T. M., D. K. Miller, J. L. Griffin, A. O. Villordon, D. O. Stephenson, K. M. Jennings, S. Chaudhari, D. C. Blouin, J. T. Copes, and T. P. Smith. 2020. Impact of reduced rates of 2,4-D and glyphosate on sweet potato growth and yield. Weed Technol. doi: https://doi.org/10.1017/wet.2020.57
• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Batts, T. M., D. K. Miller, J. L. Griffin, A. Villordon, D. O. Stephenson, IV, K. M. Jennings, S. Chaudhari, D. C. Blouin, J. T. Copes, and T. P. Smith. 2020. Impact of reduced rates of dicamba and glyphosate on sweet potato growth and yield. Weed Technol. doi: https://doi.org/10.1017/wet.2020.54.

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Target audiences for this project include crop producers and weed management professionals. 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?The results have been disseminated to communities of interest through oral and poster presentations at scientific conferences, field days, demonstrations, personal visits, newsletters, and through extension field agents. What do you plan to do during the next reporting period to accomplish the goals?Continue to evaluate older herbicide for new uses and recently released herbicides for management of weed species in Louisiana. Also, continued evaluation of new herbicide tolerant technologies in corn and soybean.

Impacts
What was accomplished under these goals? Objective and goal 1 and 2: Diverse herbicide-tolerant technologies are available in soybean and research was conducted to determine best weed management practices in the different technologies. In soybean tolerant to dicamba and glyphosate, control of barnyardgrass and glyphosate-resistant Palmer amaranth and an increase in yield was achieved only when residual herbicides were applied preemergence, but residual herbicide early-postemergence did not provide an increase in control. Control of barnyardgrass and glyphosate-resistant Palmer amaranth and soybean yield was increased in 2,4-D, glyphosate, and glufosinate tolerant soybean and in soybean that are tolerant to only glyphosate and glufosinate when residual herbicides applied preemergence and early-postemergence. Regardless of herbicide technology, entireleaf morningglory, hemp sesbania, sicklepod, prickly sida, and hophornbeam copperleaf control was greater than 90% following all treatments. The premix of glyphosate, S-metolachlor, and mesotrione is a popular postemergence herbicide utilized by corn producers in Louisiana for weed management. Research has shown that atrazine should be co-applied with the premix to broaden weed spectrum, however, the premix label restricts the atrazine rate to 0.5 lb ai/A. Research was conducted to determine if the atrazine rate should be raised to increase the levels of weed control. Preliminary results indicated that 0.5 lb ai/A of atrazine is sufficient, but research will continue.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Stephenson, IV, D. O., T. A. Spivey, M. A. Deliberto, Jr., D. C. Blouin, B. C. Woolam, and T. B. Buck. 2019. Cotton injury, growth, and yield following low-dose flumioxazin postemergence applications. J. Cotton Sci. 23:218-224.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Stephenson, IV, D. O., T. A. Spivey, M. A. Deliberto, Jr., D. C. Blouin, B. C. Woolam, and T. B. Buck. 2019. Effects of low dose flumioxazin and metribuzin postemergence applications on soybean. Weed Technol. 33:87-94. doi:10.1017/wet.2018.101.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Miller, D. and D. O. Stephenson. 2019. Herbicide/Insecticide co-application impacts in Xtend and Enlist cotton. In Proc., South. Weed Sci. Soc. 72:46.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Miller, D. and D. O. Stephenson. 2019. Impact of reduced rates of isoxaflutole on soybean growth and yield. In Proc., South. Weed Sci. Soc. 72:47.
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Miller, D. and D. O. Stephenson. 2019. Impact of reduced rates of isoxaflutole on growth and yield of cotton. In Proc., South. Weed Sci. Soc. 72:63.

Progress 06/01/18 to 09/30/18

Outputs
Target Audience:Target audiences for this project include crop producers and weed management professionals. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?One graduatestudent was trained during the project. How have the results been disseminated to communities of interest?The results have been disseminated to communities of interest through oral and poster presentations at scientific conferences, field days, demonstrations, personal visits, newsletters, and through extension field agents. What do you plan to do during the next reporting period to accomplish the goals?Continue to evaluate older herbicide for new uses and recently released herbicides for management of weed species in Louisiana. Also, continued evaluation of new herbicide tolerant technologies in corn and soybean.

Impacts
What was accomplished under these goals? Residual herbicides applied preemergence and postemergence early in the season is a good strategy to manage herbicide-resistant weeds. In Louisiana, cotton and soybean plantingcoincides and applications of residual herbicides at planting to one crop may move off-target to another crop. Research evaluated the effect of reduced rates of commonly utilized premergence residual herbicides to simulate off-target movement. Off-target movement of flumioxazin or metribuzin to unifoliate through 4-trifoliate soybean can cause significant early-season injury and some soybean width reduction. However, soybean yields were not reduced. Ragweed parthenium is a native weedy species that has begun to infest soybean production. Applying dicamba 4 to 6 weeks prior to soybean planting as a burndown controlled ragweed parthenium 90% at soybean planting. Also, preliminary control data indicates that chlorimurion-containing herbicides applied as a postemergence burndown application at planting followed by glyphosate postemergence provides approximately 70% ragweed parthenium control at season end. To control ragweed parthenium with postemergence applications in soybean, dicamba or fomesafen should be tank-mixed with glyphosate. Finally, to control ragweed parthenium just prior to soybean harvest, an application of saflufenacil alone or tank-mixed with paraquat was required. Weed management programs that utilized preemergence only, postemergence only, or preemergence followed by postemergence herbicide applications in corn did not differ in their control of barnyardgrass, entireleaf morningglory, hemp sesbania, sicklepod, and prickly sida. This indicates that Louisiana corn producers have a range of application timings to choose from for weed management. Corn in Louisiana is historically planted in early-March and summer annual weeds typically don't begin to emerge until early-April; therefore, all potential herbicide application timings occur prior to or just after weed emergence, which is a great situation for maximum herbicide efficacy.

Publications

• Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Stephenson, IV, D. O., T. A. Spivey, M. A. Deliberto, Jr., D. C. Blouin, B. C. Woolam, and T. B. Buck. 2018. Effects of low dose flumioxazin and metribuzin postemergence applications on soybean (Glycine max). Weed Technol. (in press).
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Woolam, B. C., D. O. Stephenson, IV, and D. C. Blouin. 2018. Determining seasonal emergence and control programs for henbit (Lamium amplexicaule L.). Weed Technol. (in press). doi: 10.1017/wet.2018.51
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Schwartz-Lazaro, L. M., J. K. Norsworthy, L. E. Steckel, D. O. Stephenson, IV, M. D. Bish, K. W. Bradley, and J. A. Bond. 2018. A Midsouthern consultants survey on weed management practices in soybean. Weed Technol. 32:116-125. doi:10.1017/wet.2017.109
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2018 Citation: Buck, T., D. Stephenson, B. Woolam, and J. McKibben. 2018. Growth characteristics and control of Nealleys sprangletop (Leptochloa nealleyi Vasey). In Proc., South. Weed Sci. Soc. In press
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2018 Citation: Stephenson, IV, D. O., B. C. Woolam, and T. B. Buck. 2018. Effect of simulated mesotrione drift on non-HPPD-tolerant soybean. In Proc., South. Weed Sci. Soc. In press
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Barber, T., A. Culpepper, G. Kruger, J. Norsworthy, R. Rector, G. Oakley, D. B. Reynolds, R. Scott, D. O. Stephenson, and B. Young. 2018. The effect of formulation on dicamba volatility as measured by low tunnels. In Weed Sci. Soc. America Abstr. http://wssaabstracts.com/public/54/proceedings.html
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Stephenson, IV, D. O., B. Woolam, and T. Buck. 2018. Effect of simulated isoxaflutole drift on non-HPPD tolerant soybean. In Weed Sci. Soc. America Abstr. http://wssaabstracts.com/public/54/proceedings.html
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Buck, T, A, York, D. Stephenson, B. Woolam, M. Askew, and S. Rustom. 2018. Cotton (Gossypium hirsutum L.) response to mepiquat chloride, glyphosate, and dicamba. In Weed Sci. Soc. America Abstr. http://wssaabstracts.com/public/54/proceedings.html