Source: PURDUE UNIVERSITY submitted to NRP
ADVANCING THE SUSTAINABILITY OF WEED MANAGEMENT ACROSS THE LANDSCAPE
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1010574
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2016
Project End Date
Sep 30, 2021
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
PURDUE UNIVERSITY
(N/A)
WEST LAFAYETTE,IN 47907
Performing Department
Botany & Plant Pathology
Non Technical Summary
Weed control is an important component of land management for both natural and agricultural systems. Managers must contend with invasive plant species, herbicide-resistant weeds, and increasing societal pressure to reduce herbicide use and adopt alternative control practices. Herbicide-resistant weeds in the U.S. have been estimated to cost $2 to $3 billion per year (United Soybean Board 2016). Among weed scientists, there is an increasing recognition of the need to incorporate weed ecology into management decisions and to examine alternate tools and strategies to achieve greater sustainability for weed management. At the same time, the cost and complexity of alternative practices to herbicides continues to provide a barrier for adoption for land managers, especially in agronomic crops. Thus, continued efforts to improve the stewardship of herbicide use in regards to herbicide resistance in weeds and environmental impact is well justified. This project will bring together a team with expertise in ecology, weed biology and management, and herbicide-resistance to address these challenges and to provide our clientele with research-based recommendations to improve their weed management systems. The overall goal of this proposed research is the refinement of management strategies based on a more thorough understanding of weed ecology and herbicide resistance so that weed control can be improved, inputs optimized, and selection pressure for resistance reduced.
Animal Health Component
70%
Research Effort Categories
Basic
20%
Applied
70%
Developmental
10%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2131510114020%
2131820114040%
2131460114010%
2132299114010%
2132231114010%
2131499114010%
Knowledge Area
213 - Weeds Affecting Plants;

Subject Of Investigation
1499 - Vegetables, general/other; 1460 - Tomato; 1510 - Corn; 2299 - Miscellaneous and new crops, general/other; 1820 - Soybean; 2231 - Mint;

Field Of Science
1140 - Weed science;
Goals / Objectives
The overall goal of this proposed research is the refinement of management strategies based on a more thorough understanding of weed ecology and herbicide resistance so that weed control can be improved, inputs optimized, and selection pressure for resistance reduced. We aim to address three specific objectives to achieve this goal.Assess and develop weed management strategies for new weed challenges or cropping systems using conventional and organic management practices.Examine herbicide resistance at genetic, population and landscape levels with a focus on the most recent problems with waterhemp, Palmer amaranth, and giant ragweed using new molecular tools.Collaborate in the dissemination of our research through peer-reviewed publications and extension programs.
Project Methods
Objective 1: Assess and develop weed management strategies for new weed challenges or cropping systems using conventional and organic management practices. Project A - Gibson will conduct field research in industrial hemp to 1) identify hemp cultivars that are suitable for Indiana growing conditions and 2) assess the effect of weed management on hemp growth and yields. The first experiment will be conducted at the Meigs Organic Unit. The experiment will follow a randomized complete block design with two main treatments (cultivar and planting date) and five blocks. Fifteen cultivars will be seeded in either early May or mid-June to assess the effect of planting date on cultivar performance. The experiment will be initiated in 2016 and repeated in a different section of the organic unit in 2017. The second experiment will follow a randomized complete block design with cultivar and planting date as the main treatments and four blocks. A minimum of two cultivars will be selected based on their 2016 performance and grown at multiple field sites. Three treatments will be imposed to assess the ability of hemp to compete with weeds. We will 1) cultivate mechanically between rows until crop canopy closure, 2) cultivate mechanically between rows until canopy closure and then remove visible weeds by hand until harvest, i.e. a weed-free control and 3) allow weeds to emerge throughout the growing season.Project B - Young and Johnson will conduct field research at the Southeast Purdue Agricultural Center with a focus on the integration of five cover crop species into contemporary soybean production systems in 2016 through 2017. The first experiment will establish the cover crops in the fall and then evaluate herbicide treatments for successful termination of the cover crops prior to planting soybean. The second experiment will determine the potential carryover (injurious herbicide persistence in the soil) of soil residual herbicides applied in soybean production to fall seeding of five cover crop species. Up to 19 herbicides used in soybean weed management programs will be applied to soybeans in the spring. The cover crops will be planted around the first week of September and evaluations of herbicide injury to those cover crops will proceed through the fall.Project C - Gibson, Young, Johnson, and Weller will evaluate traditional and new tactics or technologies for weed management in various agronomic and horticultural cropping systems. These techniques will involve evaluation of new herbicide candidates and herbicide-resistant crops (e.g. dicamba-tolerant soybean and 2,4-D tolerant soybean) along with along with current tools to develop improved chemical approaches that are effective in managing the diversity of herbicide-resistant or problematic in our agriculture systems. The incorporation of tillage, no-tillage and cover crops will be used to develop effective integrated weed management approaches that are not solely dependent on chemicals. This research will include small plot replicated research on-farm and at Purdue Research Centers.Project D - Johnson will conduct field and greenhouse research to examine the interaction of weeds and other plant pests. More specifically, the potential for weed species to serve as hosts for the causal agent for Goss' Wilt in corn will be investigated during the growing season and as an overwintering host.Project E - Young and Johnson will conduct field and greenhouse research on herbicide application technologies and adjuvant products that can optimize the efficiency of the dose transfer process of herbicides. The first field experiments will investigate four different spray nozzle designs with new herbicide formulations of 2,4-D and dicamba to determine the optimal application methods for weed control that will also minimize any off-target movement of the herbicides to sensitive species. The target weed species will include the most problematic species in soybean such as glyphosate-resistant marestail, waterhemp, Palmer amaranth, and giant ragweed. A second field experiment will be conducted to evaluate herbicide adjuvants for use with dicamba for control of the aforementioned weed species. The herbicide and adjuvant combinations will be evaluated to again optimize the efficacy of the herbicide application to foster greater stewardship in regards to the environment and herbicide resistance.Objective 2: Examine herbicide resistance at genetic, population and landscape levels with a focus on the most recent problems with waterhemp, Palmer amaranth, and giant ragweed using new molecular tools.Johnson, Young and Weller will conduct greenhouse, laboratory, and field experiments to confirm and characterize the distribution of Palmer amaranth, waterhemp, and giant ragweed, that are resistant to group 2, 5, 9, and 14 herbicide modes of action. Molecular marker assays and some whole-plant greenhouse screens will be performed on weed populations with suspected herbicide resistance. The molecular assays will be performed on leaf tissue collected during the growing season or from plants grown from seed in the greenhouse. The molecular assays will include those for confirmation of waterhemp resistance (glyphosate, ALS herbicides, and PPO herbicides), Palmer amaranth resistance (glyphosate, ALS herbicides), and giant ragweed (ALS herbicides). Traditional greenhouse screens will be performed for any herbicide resistance mechanisms where we don't have a molecular assay. Thus, giant ragweed resistance to group 5 and 9 herbicides will be evaluated using the whole-plant screen in the greenhouse. Weed resistance in Indiana has not yet been confirmed for glufosinate and the auxin herbicides (2,4-D or dicamba), but whole plant screens in the greenhouse will be implemented to address populations of concern as use of these herbicides are expected to increase. We will continue to investigate herbicide resistance mechanisms through basic plant physiology research related to the herbicide mode of action. Glyphosate resistance in giant ragweed will be the subject of this research so that we can discern how these mechanisms may relate to genetic spread of the resistance and management with alternative herbicides.Objective 3: Collaborate in the dissemination of our research through peer-reviewed publications and extension programs.Johnson and Weller have extension appointments and will continue to disseminate research results and develop printed and electronic materials (website, videos, webinars) to outline best management practices for weeds and integrated cropping systems. Gibson and Weller will work with cooperators to develop materials on weed management in organic for extension educators and farmers.

Progress 10/01/16 to 09/30/21

Outputs
Target Audience:The target audience for this reporting period included farmers, consultants, farm managers, and ag retail professionals in the major agronomic crops and specialty crops in Indiana. In addition, our results were directed towards fellow scientists in weed science, agronomy, basic science, across the disciplines of crop management, government agencies (e.g. NRCS, SWCS, EPA), and agricultural commodity groups. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Several graduate students, undergraduate students, three post-doctorate fellows, and two visiting scholars were involved in this research. These individuals were trained by the faculty investigators and technicians who work within these research labs. The research results were analyzed, summarized, and delivered to individuals who can utilize the information to improve weed management and enhance their professional status. More specifically, Dr. Johnson shared this information with his extension audience to help them do their job better - 15,000 farmers, 800 certified crop advisors, 1,000 commercial applicators, and 80 extension educators. Drs. Young and Gibson also participated in outreach activities (virtual meetings and teleconference) where the research results were delivered to constituents. How have the results been disseminated to communities of interest?Dr. Johnson and his extension associate Marcelo Zimmer would normally speak at approximately 80 county extension events, 5 regional extension events (crop mgt workshops), the Indiana CCA conference, the Kentuckiana CCA conference, 15 PAC field days, 15 diagnostic training center days each year. The audience of 15,000 to 20,000 people each year would normally be realized. However, COVID-19 dramatically reduced the ability to delivered face-to-face, but contact via electronic means increased our total contacts by over 200%. As stated previously, Drs. Young and Gibson also participate in outreach activities and the change in delivery mechanisms for 2019 also impacted their outreach efforts. All investigators and graduate students have presented these research findings at regional and national scientific conferences and farmer workshops. Dr. Meyers coauthored a revised weed management section of the Midwest Vegetable Production Guide for Commercial Growers, which contains recommendations for producers in eight Midwestern states and is available as both a printed guide and new online database. In addition, Dr. Meyers authored newsletter articles and delivered 12 presentations to stakeholder groups. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Dr. Gibson's lab has generated data that suggests, in contrast to reports in the scientific literature and popular press, industrial hemp may be quite impacted by competition with weeds. These results validate the research from 2019 that had similar findings. This research also indicates currently available hemp cultivars may have poor stand establishment, particularly on wet soils, and respond to delayed planting with reduced growth and early flowering. Surveys of farmers suggest that there is great interest among organic farmers in adopting hemp but concerns about how readily hemp will fit into current farm operations and certification processes. The evolution of herbicide resistance in Amaranthus species to PPO-inhibitors, glufosinate (i.e. Liberty), and synthetic auxin herbicides has been a major concern across most of the midwestern and southern U.S. crop production regions. Currently, we are using these herbicides as our primary means of controlling glyphosate-resistant weed populations, but don't expect the success to last long. Weed seed from plants with suspected resistance to key herbicides were collected by individuals in the Young and Johnson labs, or the seed was submitted by industry professionals. Based off submissions from the last six years, concern continues to grow on management of tall waterhemp and the presence of multiple resistance to the herbicide glyphosate and PPO-inhibiting herbicides. In fact, over the last year we have confirmed two populations of waterhemp in Indiana with resistance to dicamba. At one of these commercial field sites, trials conducted in 2020 and 2021 confirmed the waterhemp population also has resistance to ALS-inhibitors, HPPD-inhibitors, atrazine, and glyphosate, while also demonstrating less sensitivity to 2,4-D. Additional field research was conducted to evaluate the effectiveness of Liberty Link (glufosinate-resistant) and Xtend (dicamba + glyphosate-resistant) soybeans for improving tall waterhemp management. The use of glufosinate and dicamba integrated with other effective herbicide site of action groups does indeed show promise to help growers control tall waterhemp. However, as stated previously, the potential for tall waterhemp to evolve resistance to these technologies is significant if we don't practice sound Best Management Practices that incorporate diverse herbicide combinations and non-chemical weed management tactics. As an alternative to chemical weed control, the Young and Johnson labs evaluated the use of different designs of row cultivators in 2021 that have applications in both conventional and organic production systems. A high residue row cultivator that can be used in combination with most cover crops resulted in effective control of giant ragweed and grass species, but not perfect, as some weed survival was expected within the crop row. However, growers must be accepting of some weed survival, especially within the crop row, if we want to reduce our reliance on herbicides for weed management. Likewise, a weed electrocution toolbar was tested as a non-chemical alternative for control of weeds that have escaped management and were taller than the crop (soybean) canopy. Overall, the weed electrocution implement was effective for control of giant ragweed and reduced weed seed production to limit new weed seed introductions to the soil seedbank, a long-term weed management strategy. Finally, we have initiated extensive research to evaluate cover crops for their potential to improve control of herbicide-resistant weeds in both corn and soybeans. Our research has shown good potential to integrate cover crops with herbicides for control of winter annual weeds and summer annuals that emerge early in the spring. However, very little benefit has been observed with weeds that emerge later in the spring. Additionally, poor management of the cover crop can result in lower crop yields and interference with herbicide efficacy. We have initiated research the last two years that focuses more on the "planting green" concept that allows more cover crop biomass to accumulate in the spring to help with suppression of weeds for a longer period in the growing season. Dr. Meyers' lab conducted research to improve weed management in peppermint, watermelon, cantaloupe, pumpkin, bell pepper, onion, summer and winter squash, and tomato. Additional research was conducted to evaluate reduced herbicide doses on potted mum (dicamba, 2,4-D, glyphosate) and processing tomato (dicamba) to better understand the potential influence of off-target herbicide movement to these two specialty crops. In total, 9 greenhouse and 28 field research experiments were conducted over the last year.

Publications

  • Type: Other Status: Published Year Published: 2021 Citation: Egel, D.S. et al. 2021. Midwest Vegetable Production Guide for Commercial Growers 2021 (ID-56). West Lafayette, IN: Purdue Univ. Exten. Serv.
  • Type: Other Status: Published Year Published: 2020 Citation: Brown, C., S. Meyers, M. Rose, D. Doohan. Specialty crops at risk from dicamba and 2,4-D drift. 5-part series. North Central IPM Center.
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Harre NT, Young JM, Hager A, Young BG (2021) Soil residual herbicides: Is there a trade-off between waterhemp (Amaranthus tuberculatus) control and soybean injury and yield? Crop, Forage, & Turfgrass Management, e20097. https://doi.org/10.1002/cft2.20097
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Reinhardt Piskackova TA, Reberg?Horton SC, Richardson RJ, Jennings KM, Franca L, Young BG, Leon RG (2021) Windows of action for controlling palmer amaranth (Amaranthus palmeri) using emergence and phenology models. Weed Res 61:188-98. DOI: 10.1111/wre.12470
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Perkins CM, Gage KL, Norsworthy JK, Young BG, Bradley KW, Bish MD, Hager A, Steckel LE (2021) Efficacy of residual herbicides influenced by cover-crop residue for control of Amaranthus palmeri and A. tuberculatus in soybean. Weed Technol 35:77-81. doi: 10.1017/wet.2020.77
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Meyers, S.L., K.M. Jennings, D.K. Miller, and M.W. Shankle. 2020. Response of sweetpotato to diquat applied pre-transplanting. Weed Technology. 34:637-641
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Meyers, S.L., T.C. Barickman, J.L. Main, and T. Horgan. 2020. Yellow nutsedge (Cyperus esculentus) interference in simulated sweetpotato (Ipomoea batatas) plant beds. Weed Sci. 68:405-410
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Meyers, S.L., S. Chaudhari, K.M. Jennings, D.K. Miller, and M.W. Shankle. 2020. Response of sweetpotato to pendimethalin application rate and timing. Weed Technol. 34:301-304
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Harre NT, Duncan GW, Young JM, Young BG (2021) Relating initial paraquat injury to final efficacy in selected weed species influenced by environmental conditions. Weed Technol 35:279-88
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Haarmann, J. A., B. G. Young, and W. G. Johnson. 2021. Control of Palmer amaranth (Amaranthus palmeri) regrowth following failed applications of glufosinate and fomesafen. Weed Technol., 35:464-470
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Hodgkiss, C.L., B.G. Young, S. D. Armstrong, and W.G. Johnson. 2021. Evaluating cereal rye and crimson clover for weed suppression with within buffer areas in dicamba-resistant soybeans. Weed Technol. 35:404-411
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Hodgkiss, C.L., T.R. Legleiter, B.G. Young, and W.G. Johnson. 2021. Effects of herbicide management practices on the weed density and richness in dicamba-resistant cropping systems in Indiana. Weed Sci. 69:88-94
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Meyers, S.L., W. Guan, D. Egel, D. Nowaskie. 2021. Triploid watermelon response to flumioxazin. Weed Technology. 35:618-622


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

Outputs
Target Audience:The target audience for this reporting period included farmers, consultants, farm managers, and ag retail professionals in the major agronomic crops and specialty crops in Indiana. In addition, our results were directed towards fellow scientists in weed science, agronomy, basic science, across the disciplines of crop management, government agencies (e.g. NRCS, SWCS, EPA), and agricultural commodity groups. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Several graduate students, undergraduate students, and two post-doctorate fellows were involved in this research. These individuals were trained by the faculty investigators and technicians who work within these research labs. The research results were analyzed, summarized, and delivered to individuals who can utilize the information to improve weed management and enhance their professional status. More specifically, Dr. Johnson shared this information with his extension audience to help them do their job better - 15,000 farmers, 800 certified crop advisors, 1,000 commercial applicators, and 80 extension educators. Drs. Young and Gibson also participated in outreach activities (virtual meetings and teleconference) where the research results were delivered to constituents. How have the results been disseminated to communities of interest?Dr. Johnson and his extension associate Marcelo Zimmer would normally speak at approximately 80 county extension events, 5 regional extension events (crop mgt workshops), the Indiana CCA conference, the Kentuckiana CCA conference, 15 PAC field days, 15 diagnostic training center days each year. The audience of 15,000 to 20,000 people each year would normally be realized. However, COVID-19 dramatically reduced the ability to delivered face-to-face education. Alternatively, methods for dissemination included the production of videos and virtual meetings using a conferencing software app such as Zoom. As stated previously, Drs. Young and Gibson also participate in outreach activities and the change in delivery mechanisms for 2019 also impacted their outreach efforts. All investigators and graduate students have presented these research findings at regional and national scientific conferences and farmer workshops. Dr. Meyers coauthored a revised weed management section of the Midwest Vegetable Production Guide for Commercial Growers, which contains recommendations for producers in eight Midwestern states and will be available in December 2020 as both a printed guide and new online database. In addition, Dr. Meyers authored 20 newsletter articles, was a resource for two popular press articles, and delivered 12 presentations to stakeholder groups. What do you plan to do during the next reporting period to accomplish the goals?The same approach used in this reporting period will be used as we further our activity on this project. One area that will require a continued effort will be the research, education, and training involved with proper stewardship of Xtend soybeans as the use of dicamba in this soybean system has resulted in unacceptable levels of off-target movement to sensitive plants from 2017 through 2020. We will be developing and delivering updated training materials for 2,4-D resistant soybeans (Enlist) during the winter of 2021. With the addition of Dr. Meyers to the project in Fall 2019, we anticipate progressively greater productivity and impact from his emerging research and outreach programs in specialty crops.

Impacts
What was accomplished under these goals? Dr. Gibson's lab has generated data that suggests, in contrast to reports in the scientific literature and popular press, industrial hemp may be quite impacted by competition with weeds. These results validate the research from 2019 that had similar findings. This research also indicates currently available hemp cultivars may have poor stand establishment, particularly on wet soils, and respond to delayed planting with reduced growth and early flowering. Surveys of farmers suggest that there is great interest among organic farmers in adopting hemp but concerns about how readily hemp will fit into current farm operations and certification processes. Dr. Meyers lab conducted research to improve weed management in peppermint, watermelon, pumpkin, bell pepper, summer and winter squash, and tomato. In total, 13 greenhouse and 11 field research experiments were conducted over the last year. The evolution of PPO and synthetic auxin herbicide resistance in amaranths is a huge concern. Currently, we are using these herbicides as our primary means of controlling glyphosate resistant populations, but don't expect the success to last long. Weed seed from plants with suspected resistance to key herbicides were collected by individuals in the Young and Johnson labs, or the seed was submitted by industry professionals. Based off submissions from the last five years, concern continues to grow on management of tall waterhemp and the presence of multiple resistance to the herbicide glyphosate and PPO-inhibiting herbicides. Field research was conducted to evaluate the effectiveness of Liberty Link (glufosinate-resistant) and Xtend (dicamba + glyphosate-resistant) soybeans for improving tall waterhemp management. The use of glufosinate and dicamba integrated with other effective herbicide site of action groups does indeed show promise to help growers control tall waterhemp. However, as stated previously, the potential for tall waterhemp to evolve resistance to these technologies is significant if we don't practice sound Best Management Practices that incorporate diverse herbicide combinations and non-chemical weed management tactics. As an alternative to chemical weed control, the Young and Johnson labs have purchased a high-residue, row cultivator that can be used in both conventional and organic production systems. We demonstrated this cultivator at TAPC with good results, but a grower must be accepting of some weed survival, especially within the crop row. Integration of this cultivator with other weed control practices such as cover crops will be the focus of future research. Finally, we have initiated extensive research to evaluate cover crops for their potential to improve control of herbicide-resistant weeds in both corn and soybeans. Our research has shown good potential to integrate cover crops with herbicides for control of winter annual weeds and summer annuals that emerge early in the spring. However, very little benefit has been observed with weeds that emerge later in the spring. Additionally, poor management of the cover crop can result in lower crop yields and interference with herbicide efficacy. We have initiated research this fall that will focus more on the "planting green" concept that allows more cover crop biomass to accumulate in the spring to help with suppression of weeds for a longer period in the growing season.

Publications

  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Haarmann, J.A., B.G. Young, and W.G. Johnson. 2020. Control of waterhemp (Amaranthus tuberculatus) regrowth after failed applications of glufosinate or fomesafen. Weed Technol. https://doi.org/10.1017/wet.2020.58
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Hodgkiss, C.L., T.R. Legleiter, B.G. Young, and W.G. Johnson. 2020. Effects of herbicide management practices on the weed density and richness in dicamba-resistant cropping systems in Indiana. Weed Sci. (in press)
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Meyers, S.L., K.M. Jennings, D.K. Miller, and M.W. Shankle. 2020. Response of sweetpotato to diquat applied pre-transplanting. Weed Technology. In Press.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Meyers, S.L., T.C. Barickman, J.L. Main, and T. Horgan. 2020. Yellow nutsedge (Cyperus esculentus) interference in simulated sweetpotato (Ipomoea batatas) plant beds. Weed Sci. 68:405-410
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Meyers, S.L., S. Chaudhari, K.M. Jennings, D.K. Miller, and M.W. Shankle. 2020. Response of sweetpotato to pendimethalin application rate and timing. Weed Technol. 34:301-304
  • Type: Other Status: Published Year Published: 2020 Citation: Egel, D.S. et al. 2019/2020. Midwest Vegetable Production Guide for Commercial Growers 2020 (ID-56). West Lafayette, IN: Purdue Univ. Exten. Serv.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Desimini, S.A., K.D. Gibson, S.D. Armstrong, M. Zimmer, L.O. Maia, W. G. Johnson. 2020. Effect of cereal rye and canola on winter and summer annual weed emergence in corn. Weed Technol. 34:21-27
  • Type: Other Status: Published Year Published: 2020 Citation: Brown, C., S. Meyers, M. Rose, D. Doohan. Specialty crops at risk from dicamba and 2,4-D drift. 5-part series. North Central IPM Center.
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Harre NT, Duncan GW, Young JM, Young BG (2020) Relating initial paraquat injury to final efficacy in selected weed species influenced by environmental conditions. Weed Technol (in press)
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Ghaste M, Hayden NC, Osterholt MJ, Young J, Young B, Widhalm JR (2020) Evaluation of a Stable Isotope-Based Direct Quantification Method for Dicamba Analysis from Air and Water Using Single-Quadrupole LCMS. Molecules, 25(16), p.3649
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Harre NT, Young BG (2020) Early-season nutrient competition between weeds and soybean. Journal of Plant Nutrition 43:1887-1906
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Harre NT, Young JM, Young BG (2020) Influence of 2, 4-D, dicamba, and glyphosate on clethodim efficacy of volunteer glyphosate-resistant corn. Weed Technol 34:394-401 doi: 10.1017/wet.2019.124
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Soltani N, Oliveira MC, Alves GS, Werle R, Norsworthy JK, Sprague CL, Young BG, Reynolds DB, Brown A, Sikkema P (2020) Off-target movement assessment of dicamba in North America. Weed Technol 34:318-330. doi:10.1017/wet.2020.17
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: McCauley CL, McAdam SAM, Bhide K, Thimmapuram J, Banks JA, Young BG (2020) Transcriptomics in Erigeron canadensis reveals rapid photosynthetic and hormonal responses to auxin-herbicide application. Journal of Experimental Botany, 71:37013709, doi:10.1093/jxb/eraa124
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Whalen DM, Bish MD, Young BG, Conley SP, Reynolds DB, Norsworthy JA, Bradley KW (2020) Herbicide programs for the termination of grass and broadleaf cover crop species. Weed Technol 34:1-10 https://doi.org/10.1017/wet.2019.73
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Devkota, P., and W. G. Johnson 2020. Efficacy of dicamba and glyphosate as influenced by carrier water pH and hardness. Weed Technol. 34:101-106


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

Outputs
Target Audience:The target audience for this reporting period included farmers, consultants, farm managers, and ag retail professionals in the major agronomic crops and specialty crops in Indiana. In addition, our results were directed towards fellow scientists in weed science, agronomy, basic science, across the disciplines of crop management, government agencies (e.g. NRCS, SWCS,EPA), and agricultural commodity groups. Changes/Problems:Dr. Stephen Meyers joined the Purdue University faculty in the Department of Horticulture and Landscape Architecture in August 2019. Dr. Meyers' responsibilities include a 50% research appointment for weed management in specialty crops and has been added to this Hatch project due to our similar research interests. What opportunities for training and professional development has the project provided?Several graduate students, undergraduate students, and two post-doctorate fellows were involved in this research. These individuals were trained by the faculty investigators and technicians who work within these research labs. The research results were analyzed, summarized, and delivered to individuals who can utilize the information to improve weed management and enhance their professional status. More specifically, Dr. Johnson shared this information with his extension audience to help them do their job better - 15,000 farmers, 800 certified crop advisors, 1,000 commercial applicators, and 80 extension educators. Drs. Young and Gibson also participated in outreach activities such as field days and grower meetings where the research results were delivered to constituents. How have the results been disseminated to communities of interest?Dr. Johnson and his extension associate Marcelo Zimmer speak at approximately 80 county extension events, 5 regional extension events (crop mgt workshops), the Indiana CCA conference, the Kentuckiana CCA conference, 15 PAC field days, 15 diagnostic training center days each year. They are likely reaching an audience of 15,000 to 20,000 people each year. As stated previously, Drs. Young and Gibson also participate in outreach activities such as field days, workshops, and grower meetings. The audience for the farmer workshops that Dr. Gibson participated included both agronomic and vegetable crop farmers. Furthermore, all investigators and graduate students have presented these research findings at regional and national scientific conferences and farmer workshops. Dr. Meyers coauthored a revised weed management section of the Midwest Vegetable Production Guide for Commercial Growers, which contains recommendations for producers in eight Midwestern states and will be available in December 2019 as both a printed guide and new online database. What do you plan to do during the next reporting period to accomplish the goals?The same approach used in this reporting period will be used as we further our activity on this project. One area that will require a continued effort will be the research, education, and training involved with proper stewardship of Xtend soybeans as the use of dicamba in this soybean system resulted in unacceptable levels of off-target movement to sensitive plants in 2017, 2018, and 2019. We will be developing and delivering updated training materials for 2,4-D resistant soybeans (Enlist) during the winter of 2019/2020. With the addition of Dr. Meyers to the project, we anticipate increasing research efforts, training opportunities for undergraduate and graduate students, dissemination of research results to stakeholders, and outputs related to specialty crop weed science.

Impacts
What was accomplished under these goals? Dr. Gibson's lab has generated data that suggests, in contrast to reports in the scientific literature and popular press, industrial hemp may be quite impacted by competition with weeds. Farmers seeking to adopt industrial hemp will need to be concerned with early-season weed control. This research also indicates currently available hemp cultivars may have poor stand establishment, particularly on wet soils, and respond to delayed planting with reduced growth and early flowering. Surveys of farmers suggest that there is great interest among organic farmers in adopting hemp but concerns about how readily hemp will fit into current farm operations and certification processes. Dr. Gibson received an award in 2019 from the NIFA Organic Research and Extension Initiative (OREI) to investigate the effect of adding hemp to agronomic rotations. The evolution of PPO and synthetic auxin herbicide resistance in amaranths is a huge concern. Currently, we are using these herbicides as our primary means of controlling glyphosate resistant populations, but don't expect the success to last long. An annual screen of herbicide resistance in weeds throughout Indiana was conducted by soliciting suspect plant submissions through our Purdue University Plant and Pest Diagnostic Laboratory. Based off submissions from 2019 and the previous four years, concern continues to grow on management of tall waterhemp and the presence of multiple resistance to the herbicide glyphosate and PPO-inhibiting herbicides. Field research was conducted to evaluate the effectiveness of Liberty Link (glufosinate-resistant) and Xtend (dicamba + glyphosate-resistant) soybeans for improving tall waterhemp management. The use of glufosinate and dicamba integrated with other effective herbicide site of action groups does indeed show promise to help growers control tall waterhemp. However, as stated previously, the potential for tall waterhemp to evolve resistance to these technologies is significant if we don't practice sound Best Management Practices that incorporate diverse herbicide combinations and non-chemical weed management tactics. Finally, we have initiated extensive research to evaluate cover crops for their potential to improve control of herbicide-resistant weeds in both corn and soybeans. Our research has shown good potential to integrate cover crops with herbicides for control of winter annual weeds and summer annuals that emerge early in the spring. However, very little benefit has been observed with weeds that emerge later in the spring. Additionally, poor management of the cover crop can result in lower crop yields and interference with herbicide efficacy.

Publications

  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Campbell, T.M., J. T. Ikley, W. G. Johnson, and K. A. Wise. 2019. Impact of inoculum concentration on Gosss Wilt Development in Corn and Alternatie Hosts. Plant Health Progress 20:155-159
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Spaunhorst, D. J., N. Nie, J. R. Todd, J. M. Young, B. G. Young, and W. G. Johnson. 2019. Confirmation of herbicide resistance mutations Trp574Leu, ?G210, and EPSPS gene amplification and control of multiple herbicide-resistant Palmer amaranth (Amaranthus palmeri) with chlorimuron-ethyl, fomesafen, and glyphosate. PLoS ONE 14(3): e0214458. https://doi.org/10.1371/journal.pone.0214458
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Zimmer, M., B. G. Young, and W. G. Johnson 2019. Halauxifen-methyl preplant intervals and environmental conditions in soybean. Weed Technol. 33:680-685.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Devkota, P., and W. G. Johnson. 2019. Influence of carrier water pH, foliar fertilizer, and ammonium sulfate on 2,4-D and 2,4-D plus glyphosate efficacy. Weed Technol. 33:562-568.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Sandler, L.N., J.L. Beckerman, F. Whitford, and K. Gibson. 2019. Cannabis as conundrum. Crop Protection 117: 37-44.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Sandler, L.N. and K.D. Gibson. 2019. A call for weed research in industrial hemp (Cannabis sativa L.). Weed Research 59:255-259.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Valliant, J.C.D., K.Z. Ruhf, J.R. Brooks, K.D. Gibson, and J.R. Farmer. 2019. Fostering farm transfers from farm owners to unrelated, new farmers: A qualitative assessment of farm link services. Land Use Policy 86:438-447.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Dingha, B., L. Sandler, A. Bhowmik, C. Akotsen-Mensah, L. Jackai, K. Gibson, and R. Turco. 2019. Industrial Hemp Knowledge and Interest among North Carolina Organic Farmers in the United States. Sustainability 11. 2691. https://doi.org/10.3390/su11092691
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Zollinger R, Bernards ML, Young BG, Peterson DE, Kruger GR (2018) Efficacy of Water-Conditioning Adjuvants for Dicamba-Tolerant Soybean, in Pesticide Formulation and Delivery Systems: 38th Volume, Innovative Application, Formulation, and Adjuvant Technologies, edited by Fritz, B. and Butts, T. (West Conshohocken, PA: ASTM International, 2018), 89-97. https://doi.org/10.1520/STP161020170216
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2019 Citation: Whalen DM, Bish MD, Young BG, Conley SP, Reynolds DB, Norsworthy JA, Bradley KW (in press) Herbicide programs for the termination of grass and broadleaf cover crop species. Weed Technol
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Nie H, Mansfield BC, Harre NT, Young JM, Steppig NR, Young BG (2019) Investigating target?site resistance mechanism to the PPO-inhibiting herbicide fomesafen in waterhemp and interspecific hybridization of Amaranthus species using next generation sequencing. Pest Manag Sci https://doi.org/10.1002/ps.5445
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: McCauley CL, Young BG (2019) Differential response of horseweed (Erigeron canadensis) to halauxifen-methyl, 2,4-D, and dicamba. Weed Sci DOI:https://doi.org/10.1017/wet.2019.56
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Whalen DM, Bish MD, Young BG, Hager AG, Conley SP, Reynolds DB, Steckel LE, Norsworthy JK, Bradley KW (2019) Evaluation of cover crop sensitivity to residual herbicides applied in the previous soybean [Glycine max (L.) Merr] crop. Weed Technol 33:312-320
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Harre NT, Weller SC, Young BG (2019) An improved method to shorten physiological dormancy of giant ragweed (Ambrosia trifida) seed. Weed Sci 67:205-213


Progress 10/01/17 to 09/30/18

Outputs
Target Audience:The target audience for this reporting period included farmers, consultants, farm managers, and ag retail professionals in the major agronomic crops and specialty crops in Indiana. In addition, our results were directed towards fellow scientists in weed science, agronomy, basic science, across the disciplines of crop management, government agencies (e.g. NRCS, SWCS,EPA), and agricultural commodity groups. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Several graduate students, undergraduate students, and two post-doctorate fellows were involved in this research. These individuals were trained by the faculty investigators and technicians who work within these research labs. The research results were analyzed, summarized, and delivered to individuals who can utilize the information to improve weed management and enhance their professional status. More specifically, Dr. Johnson shared this information with his extension audience to help them do their job better - 15,000 farmers, 800 certified crop advisors, 1,000 commercial applicators, and 80 extension educators. Drs. Young and Gibson also participated in outreach activities such as field days and grower meetings where the research results were delivered to constituents. How have the results been disseminated to communities of interest?Dr. Johnson and his technician Joe Ikley speak at approximately 80 county extension events, 5 regional extension events (crop mgt workshops), the CCA conference, 15 PAC field days, 15 diagnostic training center days each year. They are likely reaching an audience of 15,000 to 20,000 people each year. During the winter of 2017/2018, an additional 200 meetings were organized to train farmers and applicators on proper use of dicamba in Xtend soybeans. Johnson and Ikley developed the educational materials that were used at these dicamba training meetings. As stated previously, Drs. Young and Gibson also participate in outreach activities such as field days, workshops, and grower meetings. The audience for the farmer workshops that Dr. Gibson participated included both agronomic and vegetable crop farmers. Furthermore, all investigators and graduate students have presented these research findings at regional and national scientific conferences and farmer workshops. What do you plan to do during the next reporting period to accomplish the goals?The same approach used in this reporting period will be used as we further our activity on this project. One area that will require a continued effort will be the research, education, and training involved with proper stewardship of Xtend soybeans as the use of dicamba in this soybean system resulted in unacceptable levels of off-target movement to sensitive plants in 2017 and again in 2018. New regulations adopted within the last month by the U.S. EPA and the Office of the Indiana State Chemist requires training of any applicator using dicamba in the Xtend soybean system. We will be developing and delivering updated training materials during the winter of 2018/2019.

Impacts
What was accomplished under these goals? Dr. Gibson completed research on the industrial hemp cultivar trial. Preliminary analysis suggests that cultivars are very sensitive to planting date likely due to their sensitivity to day length. Seed varieties were particularly sensitive, fiber varieties from Italy may be better suited for Indiana daylength. The critical period experiment was conducted during 2017 and 2018. Preliminary data suggest that, in contrast to reports in the scientific literature and popular press, industrial hemp may be quite impacted by competition with weeds. Farmer seeking to adopt industrial hemp will need to be concerned with early-season weed control. The evolution of PPO and synthetic auxin herbicide resistance in amaranths is a huge concern. Currently, we are using these herbicides as our primary means of controlling glyphosate resistant populations, but don't expect the success to last long. An annual screen of herbicide resistance in weeds throughout Indiana was conducted by soliciting suspect plant submissions through our Purdue University Plant and Pest Diagnostic Laboratory. Based off submissions from 2018 and the previous four years, concern continues to grow on management of tall waterhemp and the presence of multiple resistance to the herbicide glyphosate and PPO-inhibiting herbicides. Field research was conducted to evaluate the effectiveness of Liberty Link (glufosinate-resistant) and Xtend (dicamba + glyphosate-resistant) soybeans for improving tall waterhemp management. The use of glufosinate and dicamba integrated with other effective herbicide site of action groups does indeed show promise to help growers control tall waterhemp. However, as stated previously, the potential for tall waterhemp to evolve resistance to these technologies is significant if we don't practice sound Best Management Practices that incorporate diverse herbicide combinations and non-chemical weed management tactics. Finally, we have initiated extensive research to evaluate cover crops for their potential to improve control of herbicide-resistant weeds in both corn and soybeans. Our research has shown good potential to integrate cover crops with herbicides for control of winter annual weeds and summer annuals that emerge early in the spring. However, very little benefit has been observed with weeds that emerge later in the spring. Additionally, poor management of the cover crop can result in lower crop yields and interference with herbicide efficacy.

Publications

  • Type: Journal Articles Status: Accepted Year Published: 2018 Citation: McCauley CL, Johnson WG, Young BG (2018) Efficacy of halauxifen-methyl on glyphosate-resistant horseweed (Erigeron canadensis). Weed Sci https://doi.org/10.1017/wsc.2018.43
  • Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Zimmer M, Young BG, Johnson WG (2018) Weed control with halauxifen-methyl applied alone and in mixtures with 2, 4-D, dicamba, and glyphosate. Weed Technol doi: 10.1017/wet.2018.48
  • Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Zimmer M, Young BG, Johnson WG (2018) Herbicide programs utilizing halauxifen-methyl for glyphosate-resistant horseweed (Conyza canadensis) control in soybean. Weed Technol doi: 10.1017/wet.2018.60
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Korres NE, Norsworthy JK, Young BG, Reynolds DB, Johnson WG, Conley SP, Smeda RJ, Mueller TC, Spaunhorst DJ, Gage KL, Loux M, Kruger GR, Bagavathiannan MV (2018) Seedbank Persistence of Palmer Amaranth (Amaranthus palmeri) and Waterhemp (Amaranthus tuberculatus) across Diverse Geographical Regions in the United States. Weed Sci 66:446-456
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Harre NT, Nie H, Jiang Y, Young BG (2018) Differential antioxidant enzyme activity in rapid-response glyphosate-resistant Ambrosia trifida. Pest Manag Sci 74:2125-2132
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Kandel YR, Mueller DS, Legleiter T, Johnson WG, Young BG, Wise KA (2018) Impact of fluopyram fungicide and preemergence herbicides on soybean injury, population, sudden death syndrome, and yield. Crop Protect 106:103-109 https://doi.org/10.1016/j.cropro.2017.12.009
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Harre NT, Young JM, Young BG (2018) Environmental factors moderate glyphosate-induced antagonism of POST herbicides on the rapid response biotype of glyphosate-resistant giant ragweed (Ambrosia trifida). Weed Sci 66:301-309 https://doi.org/10.1017/wsc.2017.77
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Legleiter TR, Young BG, Johnson WG (2018) Influence of broadcast spray nozzle on the deposition, absorption, and efficacy of dicamba plus glyphosate on four glyphosate-resistant dicot weed species. Weed Technol 32:174-181 https://doi.org/10.1017/wet.2017.104
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Legleiter TR, Young BG, Johnson WG (2018) Glyphosate plus 2, 4-D deposition, absorption, and efficacy on glyphosate-resistant weed species as influenced by broadcast spray nozzle. Weed Technol 32:141-149 https://doi.org/10.1017/wet.2017.88
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Van Horn CR, Moretti ML, Robertson RR, Segobye K, Weller SC, Young BG, Johnson WG, Schulz B, Green AC, Jeffery T, Lesp�rance MA, Tardif FJ, Sikkema PH, Hall CJ, McLean MD, Lawton MB, Sammons DR, Wang D, Westra P, Gaines TA (2018) Glyphosate resistance in Ambrosia trifida: Part 1. Novel rapid cell death response to glyphosate. Pest Manag Sci 74:1071-1078 doi:10.1002/ps.4567
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Moretti ML, Van Horn CR, Robertson R, Segobye K, Weller SC, Young BG, Johnson WG, Sammons DR, Wang D, Ge X, d'Avignon A, Gaines TA, Westra P, Green AC, Jeffery T, Lesp�rance MA, Tardif FJ, Sikkema PH, Hall CJ, McLean MD, Lawton MB, Schulz B (2018) Glyphosate resistance in Ambrosia trifida: Part 2. Rapid response physiology and non-target site resistance. Pest Manag Sci 74:1079-1088 doi:10.1002/ps.4569
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Spaunhorst, D., Devkota, P., Johnson, W., Smeda, R., Meyer, C., & Norsworthy, J. (2018). Phenology of Five Palmer amaranth (Amaranthus palmeri) Populations Grown in Northern Indiana and Arkansas. Weed Science, 66(4), 457-469. doi:10.1017/wsc.2018.12


Progress 10/01/16 to 09/30/17

Outputs
Target Audience:The target audience for this reporting period included farmers, consultants, farm managers, and ag retail professionals in the major agronomic crops and specialty crops in Indiana. In addition, our results were directed towards fellow scientists in weed science, agronomy, basic science, across the disciplines of crop management, government agencies (e.g. NRCS, SWCS, EPA), and agricultural commodity groups. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Several graduate students, undergraduate students, and two post-dosctorate fellows were were involved in thisresearch. These individuals were trained by the faculty investigators and technicians who work within these research labs. The research results were analyzed, summarized, and delivered to individuals who can utilize the information to improve weed management and enhance their professional status. More specifically, Dr. Johnsonshared this information with hisextension audience to help them do their job better - 15000 farmers, 800 certified crop advisors, 1000 commercial applicators, and 80 extension educators. Drs. Young and Gibson also participated in outreach activities such as field days and grower meetings where the research results were to delivered to constituents. How have the results been disseminated to communities of interest?Dr. Johnson and his technician Joe Ikley speak at approximately 80 county extension events, 5 regional extension events (crop mgt workshops), the CCA conference, 15 PAC field days, 15 diagnostic training center days each year. They are likely reaching an audience of 15,000 to 20,000 people each year. As stated previously, Drs. Young and Gibson also particpate in outreach activities such as field days, workshops, and grower meetings. The audience for the farmer workshops that Dr. Gibson particpated included both agronomic and vegetable crop farmers. Furthermore, all investigators and graduate students have presented these reserach findings at regional and national scientific conferences and farmer workshops. What do you plan to do during the next reporting period to accomplish the goals?The same approach used in this reporting period will be used as we further our activity on this project. One potential area that will require a significant increase in effort will be the research,education, and training involved with proper stewardship of Xtend soybeans as the use of dicamba in this soybean system resulted in unacceptable levels of off-target movement to sensitive plants in 2017. New regulations adopted in the past few months by the U.S. EPA and the Office of the Indiana State Chemist requires training of any applicator using dicamba in the Xtend soybean system.

Impacts
What was accomplished under these goals? Dr. Gibson completed research on the industrial hemp cultivar trial. Preliminary analysis suggests that cultivars are very sensitive to planting date likely due to their sensitivity to day length. Seed varieties were particularly sensitive, fiber varieties from Italy may be better suited for Indiana daylength. The critical period experiment was conducted during 2017. Preliminary data suggest that, in contrast to reports in the scientific literature and popular press, industrial hemp may be quite impacted by competition with weeds. Farmer seeking to adopt industrial hemp will need to be concerned with early-season weed control. The critical period experiment will be continued in 2018. The evolution of PPO and synthetic auxin herbicide resistance in amaranths is a huge concern. Currently, we are using these herbicides as our primary means of controlling glyphosate resistant populations, but don't expect the success to last long. An annual screen of herbicide resistance in weeds throughout Indiana was conducted by soliciting suspect plant submissions through our Purdue University Plant and Pest Diagnostic Laboratory. Based off submissions from 2017 and the previous three years, concern continues to grow on management of tall waterhemp and the presence of multiple resistance to the herbicide glyphosate and PPO-inhibiting herbicides. Field research was conducted to evaluate the effectiveness of Liberty Link (glufosinate resistant) and Xtend (dicamba + glyphosate resistant) soybeans for improving tall waterhemp management. The use of glufosinate and dicamba inegrated with other effective herbicide site of action groups does indeed show promise to help growers control tall waterhemp. However, as stated previously, the potential for tall waterhemp to evlaove resistance to these technologies is significant if we don't practice sound Best Management Practices that incorporate diverse herbicide combinations and non-chemical weed management tactics. Herbicide efficacy can be negatively influenced by spray solution pH, hardness and foliar fertilizers., Herbicide stability in spray solutions can be negatively impacted by extremes in pH. However, storage stability doesn't vary much over a wide range of storage temperatures. The use of ammonium sulfate has been a common adjuvant used with herbicides to condition water quality for use as a spray carrier. However, the use of ammonium sulfate with the herbicide dicamba will increase dicamba volatility from traget surfaces and result in off-target movement. Thus, alternatives to ammonium sulfate with glyphosate and dicamba combiantions has been the focus of field and greenhouse resarch. To date, no alternative adjuvanthas show the potential to provide equivlaent efficacy as ammonium sulfate when combined with glyphosate and dicamba. In addition, the spray nozzles and dirft reduction adjuvants required for use with dicamba applications can reduce herbicide efficacy. Thus, dicamba applications performed in Xtend soybeans are not optimized for herbicide activity because of the application requirements implement to reduce off-target movement. This will hasten the evoltuion of weeds resistant to dicamba. Dr. Johnson has condintued his research across pest disciplines (weeds and plant pathology). The recent findings have demonstrated that there are a few commonly found weeds that can serve as alternative hosts for Goss's wilt disease in corn, specifically grass weeds.

Publications

  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Moretti ML, Van Horn CR, Robertson R, Segobye K, Weller SC, Young BG, Johnson WG, Sammons DR, Wang D, Ge X, d'Avignon A, Gaines TA, Westra P, Green AC, Jeffery T, Lesp�rance MA, Tardif FJ, Sikkema PH, Hall CJ, McLean MD, Lawton MB, Schulz B (2017) Glyphosate resistance in Ambrosia trifida: Part 2. Rapid response physiology and non-target site resistance. Pest Manag Sci doi:10.1002/ps.4569
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Farmer JA, Bradley KW, Young BG, Steckel LE, Johnson WG, Norsworthy JK, Loux MM (2017) Influence of tillage methods on management of Amaranthus species in soybean. Weed Technol 31:10-20
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Zollinger RK, Howatt K, Bernards ML, Young BG (2016) Ammonium Sulfate and Dipotassium Phosphate as Water Conditioning Adjuvants. Pesticide Formulation and Delivery Systems: 35th Volume, Pesticide Formulations, Adjuvants, and Spray Characterization in 2014, STP158720140126, G. Goss, Ed., ASTM International, West Conshohocken, PA, pp. 42-51, https://doi.org/10.1520/STP158720140126
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Meyer CJ, Norsworthy JK, Young BG, Steckel LE, Bradley KW, Johnson WG, Loux MM, Davis VM, Kruger GR, Bararpour MT, Ikley JT, Spaunhorst DJ, Butts TR (2016) Early-season Palmer amaranth and waterhemp control from preemergence programs utilizing 4-hydroxyphenylpyruvate dioxygenaseinhibiting and auxinic herbicides in soybean. Weed Technol 30:67-75
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Kohrt JR, Young JM, Matthews JL, Young BG (2016) Influence of nitrogen status on the sensitivity of glyphosate-resistant and -susceptible tall waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri). Weed Sci 64:735-742
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Schwartz LM, Gibson DJ, Young BG. (2016) Using integral projection models to compare population dynamics of four closely related species. Popul Ecol 58:285-292
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Schwartz LM, Gibson DJ, Young BG (2016) Do plant traits predict the competitive abilities of closely related species? AoB PLANTS 8: plv147; doi:10.1093/aobpla/plv147
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Schwartz LM, Norsworthy JA, Young BG, Bradley KA, Kruger GR, Davis VM, Steckel LS, Walsh M. (2016) Tall waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri) seed production and retention at soybean maturity. Weed Technol 30:284-290
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Butts TR, Norsworthy JA, Kruger GR, Sandell L, Young BG, Steckel LS, Loux MM, Bradley KA, Conley S, Stoltenberg D, Arriaga FJ, Davis VM (2016) Management of pigweed (Amaranthus spp.) in glufosinate-resistant soybean in the Midwest and Midsouth. Weed Technol 30:355-365
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Spaunhorst, D. J., and W. G. Johnson. 2017. Variable tolerance among Palmer amaranth (Amaranth palmeri) biotypes to glyphosate, 2,4-D amine, and premix formulation of glyphosate + 2,4-D choline. ISSN: 0043-1745 , 1550-2759; DOI: 10.1017/wsc.2017.50 Weed science , 2017, Vol.65(6), p.787-797
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Heneghan, J. M., and W. G. Johnson. 2017. The growth and development of five waterhemp (Amaranthus tuberculatus) populations in a common garden. ISSN: 0043-1745 , 1550-2759; DOI: 10.1017/wsc.2016.20 Weed science , 2017, Vol.65(2), p.247-255
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Devkota, P, and W. G. Johnson. 2016. Glufosinate efficacy as influenced by carrier water pH, foliar fertilizer, and ammonium sulfate. ISSN: 0890-037X , 1550-2740; DOI: 10.1614/WT-D-16-00053.1 Weed Technology , 2016, Vol.30(4), p.848-859
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Devkota, P., and W. G. Johnson. 2016. Effect of carrier water hardness and ammonium sulfate on efficace of 2,4-D choline and premixed 2,4-D choline plus glyphosate. ISSN: 0890-037X , 1550-2740; DOI: 10.1614/WT-D-16-00040.1 Weed technology , 2016, Vol.30(4), p.878-887
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Devkota, P., D. J. Spaunhorst, and W. G. Johnson. 2016. Effect of carrier water pH, hardness, foliar fertilizer and ammonium sulfate on mesotrione efficacy. ISSN: 0890-037X , 1550-2740; DOI: 10.1614/WT-D-16-00019.1 Weed Technology , 2016, Vol.30(3), p.617-628
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Legleiter, T. R. and W. G. Johnson. 2016. Herbicide coverage in narrow row soybean as influenced by spray nozzle design and carrier volume. ISSN: 0261-2194 , 1873-6904; DOI: 10.1016/j.cropro.2016.01.009 Crop Protection , 2016, Vol.83, p.1-8
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Spaunhorst, D. J., and W. G. Johnson. 2016. Palmer amaranth control with preplant herbicide programs containing dicamba, isoxaflutole, and 2,4-D. ISSN: 2374-3832; DOI: 10.2134/cftm2015.0173 Crop, Forage & Turfgrass Management. , 2016, Vol.2(1), p.0
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Regnier, E.E., S.K. Harrison, M. M. Loux, C. Holloman, R. Venkatesh, F. Diekman, R. Taylor, R. A. Ford, D.E. Stoltenberg, R. G. Hartzler, A. S. Davis, B. J. Schutte, J. Cardidina, K. J. Mahoney, W. G. Johnson. 2016. Certified crop advisors perceptions of giant ragwed (Ambrosia trifida) distribution, herbicide resistance and management in the corn belt. ISSN: 0043-1745 , 1550-2759; DOI: 10.1614/WS-D-15-00116.1 Weed Science , 2016, Vol.64(2), p.361-377
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Devkota, P., F. Whitford, and W. G. Johnson. 2016. Influence of spray solution temperature and holding duration on weed control with premixed glyphosate and dicamba formulation. ISSN: 0890-037X , 1550-2740; DOI: 10.1614/WT-D-15-00101.1 Weed Technology , 2016, Vol.30(1), p.116-122
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Ikley, J., W. Johnson, and K. Wise. 2016. Defining the alternative host range and the effect of herbicides on the pathogenicity of Clavibacter michiganensis supsp nebraskensis, causal agent of Gosss wilt of corn. ISSN: 0031-949X Phytopathology. , 2016, Vol.106(1), p.S4
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Hollandbeck, G. A., W. G. Johnson, and K. A. Wise. 2016. Effect of volunteer corn density on deoxynivalenol production by Fusarium graminearum. ISSN: 0031-949X Phytopathology. , 2016, Vol.106(1), p.S3
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Giacomini DA, Umphres AM, Nie H, Mueller TC, Steckel LE, Young BG, Scott RC, Tranel PJ (2017) Two new PPX2 mutations associated with resistance to PPO?inhibiting herbicides in Amaranthus palmeri. Pest Manag Sci 73:15591563 doi:10.1002/ps.4581
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Harre NT, Nie H, Robertson RR, Johnson WG, Weller SC, Young BG (2017) Distribution of herbicide-resistant giant ragweed (Ambrosia trifida) in Indiana and characterization of distinct glyphosate-resistant biotypes. Weed Sci 65:699-709
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Loux MM, Dobbels T, Bradley KE, Johnson WG, Young BG, Spaunhorst DJ, Norsworthy JK, Steckel LE (2017) Influence of cover crops on management of Amaranthus spp. in glyphosate- and glufosinate-resistant soybean. Weed Technol 31:487-495
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Van Horn CR, Moretti ML, Robertson RR, Segobye K, Weller SC, Young BG, Johnson WG, Schulz B, Green AC, Jeffery T, Lesp�rance MA, Tardif FJ, Sikkema PH, Hall CJ, McLean MD, Lawton MB, Sammons DR, Wang D, Westra P, Gaines TA (2017) Glyphosate resistance in Ambrosia trifida: Part 1. Novel rapid cell death response to glyphosate. Pest Manag Sci doi:10.1002/ps.4567