The extension weed science programs at The Ohio State University, Purdue University, and the University of Illinois recently collaborated to revise suggestions and precautions for use of dicamba in dicamba-resistant soybean. The United States Environmental Protection Agency renewed labels of Xtendimax, Engenia, and FeXapan last October, and this updated extension weed science publication offers additional suggestions to help further reduce off-target dicamba movement.
The weed science programs at Southern Illinois University and the University of Illinois are participating in a research project sponsored by the United Soybean Board to survey and monitor the potential for the evolution of weeds with resistance to glufosinate and dicamba. Early detection of evolved resistance to these herbicides could alert soybean farmers of the imposing threat in time for changes in management strategies that avoid herbicide failures. Researchers in Illinois will collect seed from at least two of our most challenging weed species, waterhemp and horseweed (a.k.a. marestail). We also would like to collect seed from Palmer amaranth and could benefit from your assistance.
If you know of Palmer amaranth populations in soybean fields around the state from which we could collect seed, please let us know. Contact Dr. Karla Gage at Southern Illinois University (618-453-7679, or firstname.lastname@example.org) for Palmer amaranth populations south of Interstate 70, or Dr. Aaron Hager at the University of Illinois (217-333-9646, email@example.com) for populations north of Interstate 70 and we’ll make arrangements to collect seed prior to harvest.
The University of Illinois Extension will host the Ewing Demonstration Center Agronomy Field Day on Thursday, July 26, 2018 at 9 a.m. Every growing season presents challenges to production, and this year is no exception! We are happy to host this summer field day to share with local growers current, ongoing agronomy research in southern Illinois, including cover crop trials on corn and soybeans, nitrogen management in corn, weed management in soybean, and our continuous no-till field, now in its 50th year of continuous no-till production.
We are highlighting our 50th year of continuous no-till production in our field day this year. This no-till trial area was established in 1969 by George McKibben, the “Father of No-Till”, long-time agronomist and researcher at the Dixon Springs Ag Center in southern Illinois. This plot has been cropped utilizing no-till production of corn and soybeans ever since. The “zero-till” system as it was first called, was researched to “save the soil” that was lost over the many years of intensive tillage required to raise grain crops on the sloping hills of southern Illinois with the planting equipment available at the time.
In honor of this milestone, we will have the original “zero-till planter” on display. This planter was modified and built in the early 1960s at the Dixon Springs Ag Center and used there and also at the Ewing Demonstration Center and other research sites. The demonstrated success of this zero-till planter and production system was one of the inspirations that led companies like Allis-Chalmers and John Deere to start engineering and producing no-till planting equipment. Also, joining us for the field day will be Donnie Morris, retired farm mechanic and engineer who built this planter, along with other retired Extension advisors and educators that worked at the Ewing Demonstration Center over the years.
The topics to be discussed at Field Day include:
Looking Back at 50 Years of Continuous No-till
- Current and Retired Staff, University of Illinois
Insect Management in Corn and Soybean
- Nick Seiter, Research Assistant Professor, University of Illinois
What We Have Learned After 48 Years of Continuous No-till
- Ron Krausz, Manager SIU Belleville Research Center
- Sarah Dintelmann, Undergraduate Assistant ,Weed Science, SIU
Managing Cover Crops in Corn and Soybean
- Nathan Johanning, Extension Educator, University of Illinois
Intro to Corn Genetics: Why is Sweet Corn Sweet?
- Talon Becker, Extension Educator, University of Illinois
Please join us for Agronomy Field Day to help celebrate this milestone in crop production! The field day is free and open to anyone interested, and lunch will be provided. Certified Crop Advisor CEUs will also be offered (Soil & Water – 2.0; IPM – 0.5, Crop Management – 0.5). The Ewing Demonstration Center is about 20 minutes south of Mt. Vernon located at 16132 N. Ewing Rd; Ewing, IL 62836, on the north edge of the village of Ewing, north of the Ewing Grade School on north Ewing Road. Watch for signs.
To help us provide adequate lunch and materials, please RSVP to the University of Illinois Extension Office in Franklin County at 618-439-3178 by Tuesday, July 24. For additional information on the field day, contact Marc Lamczyk at the Franklin County office or firstname.lastname@example.org.
We would like to take this opportunity to once again extend the invitation to attend the 2018 University of Illinois Weed Science Field Day, to be held Wednesday, June 27th at the University of Illinois Crop Sciences Research and Education Center, located immediately south of the main campus on South Wright Street. Coffee and refreshments will be available under the shade trees near the Seed House beginning at 8:00 a.m. The tour will provide ample opportunity to look at research plots and interact with weed science faculty, staff, and graduate students. Participants can compare their favorite corn and soybean herbicide programs to other commercial programs. The tour will conclude around noon with a catered lunch at the Seed House. Cost for the Urbana weed science field tour is $10, which will help defray the cost of the field tour book, refreshments and lunch.
We look forward to visiting with you at the Urbana weed science field day on June 27th. If you have any questions about the weed science field research tour, please feel free to call Charlie Mitsdarfer (217-621-7717) or Aaron Hager (217-621-8963).
The following article was written by Lauren Quinn, media specialist in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois. The article describes recently publiched research, lead by Dr. Adam Davis, a research ecologist with USDA-ARS and adjunct professor in the Department of Crop Sciences, that examined cooperative weed management as a tool used against the challenges of herbicide-resistant waterhemp. The following quote from Dr. Davis succinctly summarizes the research: “The crux of the story is that if you do good stuff and you aggregate it at larger spatial scales, it gets even better. If you do bad stuff and you aggregate it at large spatial scales, it gets even worse.” I hope this information will be helpful and beneficial as you plan your future weed management programs.
In the fight against herbicide resistance, farmers are working with a shrinking toolkit. Waterhemp, a weedy nemesis of corn and soybean farmers, has developed resistance to multiple herbicide modes of action, often in the same plant. Even farmers using the latest recommendations for tank mixtures are fighting an uphill battle, with long-distance movement of pollen and seeds bringing the potential for new types of resistance into their fields each year.
In a study released this week, scientists at the University of Illinois and USDA’s Agricultural Research Service offer a new tool that is not only highly effective, it’s free. All it costs is a conversation.
“I think we’re at a point now where farmers are looking for new tools. This tool is free, but it requires that people talk to each other and work together as opposed to doing everything on their own,” says Adam Davis, research ecologist with USDA-ARS and adjunct professor in the Department of Crop Sciences at U of I.
The tool is cooperative weed management – in other words, making decisions about how to manage herbicide-resistant weeds in cooperation with neighboring farms. The more farms working together, and the larger area covered, the better.
Davis and his team tested the efficacy of farmer cooperation using a computer simulation of waterhemp resistance evolution through time and space. They ran the simulation using real numbers and management practices from the past, starting in 1987, to arrive at a realistic representation of herbicide resistance in waterhemp in 2015. Then they forecast 35 years into the future to determine how resistance might change under different management and cooperation scenarios.
“The crux of the story is that if you do good stuff and you aggregate it at larger spatial scales, it gets even better. If you do bad stuff and you aggregate it at large spatial scales, it gets even worse,” Davis says.
The “bad stuff,” according to the simulation, is using a single herbicide mode of action year after year. Resistance to a single chemical evolved and spread very quickly throughout the simulated landscape, especially if everyone was spraying the same one every year.
“If you take the cheap route, you’ll save some money in the short term on your herbicide costs, but in the long term, you’ll have a much greater likelihood of developing resistance,” Davis notes.
But if farmers invested in tank mixtures of herbicides representing three or four modes of action, the evolution and spread of resistance was delayed, and the delay got longer with increasing levels of cooperation.
“The message is not to use the most expensive herbicide program possible; the message is to use the available tools to manage your weeds better,” Davis says. “If you do that on your own farm, certainly it’s going to help. If you do it on a bunch of adjoining farms, it’s going to help even more. You can buy a couple of decades of time, in terms of delaying herbicide resistance evolution, by aggregating the best practices at large spatial scales.”
The simulation looked at management on individual farms, cooperatives of 10 neighboring farms, and cooperative weed management areas, comprising 10 neighboring farmer cooperatives. Davis says the specific number of farms making collective weed management decisions isn’t as important as the spatial scale they cover. He suggests forming weed management areas at the township scale and above.
The concept is simple, but farmers treasure their independence. How will it work?
Davis points to existing regional farm associations, such as drainage districts or commodity groups, as possible models for how weed management cooperatives might operate. He also suggests involving custom applicators in decision-making and implementation, since they’re already out there servicing multiple farms in a region.
The researchers are asking additional questions of the simulation, adding non-chemical control options like cover crops, crop rotation, and the Harrington Seed Destructor, to see how much more effective they get at larger scales. They’re also trying to quantify how much non-compliance a cooperative weed management area can withstand before its effectiveness falls apart.
But for now, the study suggests preserving the effectiveness of existing herbicides is worth the trouble of making nice with the neighbors.
The article, “Confronting herbicide resistance with cooperative management,” is published in Pest Management Science [DOI: 10.1002/ps.5105]. Co-authors include Jeffrey Evans, Alwyn Williams, Aaron Hager, Steven Mirsky, Patrick Tranel, and Adam Davis. The research was supported by USDA NIFA AFRI Award 2012-67013-19343, and is part of the USDA-ARS Area-Wide Pest Management Project.
Soil-residual herbicides are important components of integrated weed management programs. Reducing the number of weeds exposed to foliar-applied herbicides helps reduce the selection intensity for weeds resistant to foliar-applied herbicides. Residual herbicides applied with postemergence soybean herbicides also can reduce the need for a second postemergence application. However, simply applying a soil-residual herbicide does not guarantee the product will provide the desired level or duration of weed control. Many edaphic and environmental factors influence the level of weed control achieved by soil-residual herbicides.
Soil-residual herbicides applied with postemergence herbicides require precipitation to move them into the soil solution where they are available for uptake. Herbicide effectiveness is reduced when a soil-residual herbicide is sprayed on a dry soil surface with no precipitation for several days following application. Residual herbicides generally require 0.5 to 1.0 inch of precipitation within 7 to10 days after application for optimal incorporation. Soil condition, soil moisture content, residue cover, and the chemical properties of the herbicide influence how much and how soon after application precipitation is needed for optimal activity.
Also, keep in mind the labels of soil-residual products include a maximum soybean growth stage or time interval prior to harvest beyond which an application cannot be made. A sample of these growth stages and preharvest intervals is presented in Table 1.
Table 1. Maximum soybean growth stage or preharvest interval for foliar application of soil-residual herbicides.
|Herbicide||Maximum soybean growth stage for broadcast application|
|Anthem Maxx||Through the third trifoliate leaf stage|
|Dual Magnum/EverpreX||Do not apply within 90 days of harvest|
|Dual II Magnum||Through the third trifoliate leaf stage|
|FirstRate||Before soybean reach growth stage R2|
|Prefix||Do not apply within 90 days of harvest|
|Sequencea||Do not apply within 90 days of harvest|
|Warrant/Warrant Ultra||Before soybean reach growth stage R2|
|Zidua||Third trifoliate stage|
aApply postemergence only to glyphosate-resistant soybean varieties.
The labels of most postemergence corn herbicides allow applications at various crop growth stages, but almost all product labels indicate a maximum growth stage beyond which broadcast applications should not be made, and a few even a state minimum growth stage before which applications should not be made. These growth stages are usually indicated as a particular plant height or leaf stage; sometimes both of these are listed. For product labels that indicate a specific corn height and growth state, be sure to follow the more restrictive of the two. Application restrictions exist for several reasons, but of particular importance is the increased likelihood of crop injury if applications are made outside a specified growth stage or range. The following table lists the maximum corn growth stage for broadcast application of several postemergence corn herbicides. Be sure to constult the respective product label for additional precautions or restrictions.
Table 1. Postemergence herbicide application timings based on corn growth stage(s).
|Herbicide||Maximum corn heights and/or growth stagesa|
|2,4-D||Broadcast before corn exceeds 8” tall; use drop nozzles when corn is taller than 8”.|
|Accent Q||Broadcast up to 20” tall or through the V6 stage. Apply with drop nozzles when corn is 20–36” tall or before the V10 stage.|
|Anthem Maxx||Apply from corn emergence through the V4 (visible fourth leaf collar) stage.|
|Armezon Pro||Apply from corn emergence to the 8-leaf stage or 30” tall. Use directed applications when corn is 12–30” tall.|
|Atrazine||Apply before corn exceeds 12” tall.|
|Basagran||No height specified on label.|
|Basis Blend||Apply to corn from spike through 2 collar stage. Do not apply to corn having 3 fully emerged collars or over 6” tall.|
|Cadet||Apply until corn is 48″ tall or prior to tasseling.|
|Callisto/Callisto GT||May be applied to corn up to 30” tall or up to the 8-leaf stage.|
|Callisto Xtra||Apply before corn exceeds 12” tall|
|Capreno||Broadcast applications may be made to corn from the 1-leaf collar stage up to 20” tall. Do not apply if corn is more than 20” tall or exhibiting 7 or more leaf collars.|
|Clarity or Banvel||Apply between corn emergence and the 5-leaf stage or 8” tall; apply 0.5 pt/A rate when corn is 8 to 36” or if 6th leaf is emerging, or if 15 days prior to tassel emergence. Do not apply when soybean are growing nearby if: 1) corn is more than 24” tall, 2) soybean are more than 10” tall, 3) soybean have begun to bloom.|
|DiFlexx||Apply broadcast to corn from spike through V10 growth stage or 36” tall, whichever occurs first.|
|DiFlexx Duo||Apply broadcast to corn from emergence up to, but not including, V7 or 30” tall, whichever occurs first. Can be applied as a directed spray from V7 through V10, up to 36” tall corn, or up to 15 days prior to tassel, whichever occurs first.|
|Enlist One/Duo||Apply when corn is no larger than V8 or 30” tall, whichever is more restrictive. Directed applications can be made to corn up to 48” tall.|
|Glyphosate (glyphosate-resistant corn)||Apply broadcast through the V8 stage or until corn reaches 30” tall. Use drop nozzles for applications to corn 30–48” tall.|
|Halex GT (glyphosate-resistant corn)||Apply to corn up to 30″ tall or the 8-leaf stage.|
|Harmony SG||Apply to 2–6 leaf corn with 1–5 collars or up to 16” tall.|
|Harness Max||Apply until corn reaches 11” tall.|
|Hornet WDG||Apply broadcast until corn reaches 20” tall or V6 stage. Apply with drop nozzles to corn up to 36” tall.|
|Impact/Armezon||Can be applied up to 45 days before harvest. Do not apply Armezon past the V8 growth stage.|
|Impact Z||Apply before corn exceeds 12” tall.|
|Laudis||Apply up to the V8 growth stage.|
|Liberty (glufosinate-resistant corn)||Broadcast until corn at the V6 growth stage. Use drop nozzles for up to 36” tall.|
|Marksman||Apply between corn emergence and the 5-leaf or 8” height stage.|
|Moxy||Apply prior to tassel emergence.|
|NorthStar||Broadcast applications are made when corn is between 4 –20” tall (V2–V6). Use directed applications when corn is 20–36” tall.|
|Permit||Can be applied from spike through layby.|
|Realm Q||May be broadcast applied to corn up to 20” tall or exhibiting 6 leaf collars.|
|Require Q||Apply to corn 4–20” tall. Do not apply to corn exhibiting 7 or more leaf collars.|
|Resolve Q||Do not apply to corn taller than 20” or exhibiting 7 or more leaf collars.|
|Resource||Apply to corn from the 2-leaf through 10-leaf stage.|
|Revulin Q||Do not apply to corn taller than 30” or that exhibits 8 or more collars.|
|Solstice||May be applied broadcast up to the V8 growth stage or 30” tall.|
|Starane Ultra||Apply broadcast to corn with up to 5 fully exposed leaf collars (V5).|
|Status||Can be applied to corn between 4” (V2) and 36” (V8) tall.|
|Steadfast Q||Apply to corn up to 20” tall and exhibiting up to 6 leaf collars.|
|Stinger||Apply to corn from emergence through 24” tall.|
|Yukon||Apply broadcast or with drop nozzles to corn from spike to 36” tall. Drop nozzles are recommended when corn exceeds 20”.|
|Zemax||May be applied after corn emergence until plants reach 30” tall or up to the V8 stage.|
a When maximum application timings are indicated by two corn growth stages, follow the most restrictive of the two.
The weed science program at the University of Illinois invites all weed management practitioners to our annual weed science field tour, which will be held on Wednesday, June 27 at the Crop Sciences Research and Education Center (a.k.a. South Farm), located south of campus on Wright Street extended. Registration will begin at 8:00 a.m. and refreshments (coffee, juice, and doughnuts) will be available. Preregistration is not required, but please let us know in advance if you will be bringing a large group of participants so we can plan accordingly for meals.
Similar to past years, we will car pool to the fields where participants can join in a guided (but informal) tour format. The tour will provide ample opportunity to look at research plots and interact with weed science faculty, staff, and graduate students. Participants can compare their favorite corn and soybean herbicide programs to other commercial programs and get an early look at a few new products that soon will be on the market. The tour will conclude around noon with a catered lunch at the Seed House.
Cost for the Urbana weed science field tour is $10, which will help defray the cost of the field tour book, refreshments and lunch. We will apply for 2 hours of CCA credit under the IPM category. If you have any questions about the weed science field research tour, please feel free to call Charlie Mitsdarfer (217-621-7717) or Aaron Hager (217-621-8963).
Beginning in 1949, a conference was organized by faculty and staff from several departments at the University of Illinois to provide clientele and stakeholders with the latest pest management research and recommendations. The conference was brought into existence by Dr. H.B. “Pete” Petty, the first extension entomologist with the Cooperative Extension Service at the University of Illinois, to meet the educational needs of Illinois pest management practitioners. From its inception in 1949 through 1986, the conference was known as the Illinois Custom Spray Operators’ Training School (often referred to as Spray School), but was renamed as the Illinois Agricultural Pesticides Conference in 1987, and renamed again as the Illinois Crop Protection Technology Conference in 1999. Speakers at this conference presented current research and recommendations for management of weeds, insects, and diseases for a variety (depending on the era) of Illinois crops. The conference represents a 60-year history of pests and pest management in Illinois cropping systems.
Perhaps unknown to some, the history of the conference was recorded in an annual conference proceedings. Through the efforts of Professors emeriti Kevin Steffey and Michael Gray, these proceedings now can be accessed electronically at:
I invite everyone to take a few moments and browse the history of Illinois agriculture chronicled in these proceedings. Don’t be surprised to find some of the first references to pest management principles that we now routinely teach in academic classes and extension meetings. Enjoy!
It’s difficult to recall the debut of a weed management technology that generated more divisiveness than the 2017 introduction of dicamba-resistant soybean varieties and the accompanying use of dicamba. Damage to off-target vegetation from myriad sources of exposure resulted in not only monetary losses, but also untold costs to professional and personal relationships. Trust that took years to build was damaged or lost in the span of one growing season. This includes the public trust in pesticide use.
The United States Environmental Protection Agency (EPA), in response to the unprecedented number of complaints, issued several amendments to the XtendiMax, Engenia, and FeXapan labels last October that will impact all purchases and applications of these products in 2018 and beyond. The intent of these label amendments is to reduce sensitive plant species exposure to dicamba primarily through physical movement (i.e., drift during the application or particle movement during temperature inversions) or via dicamba residues dislodged from application equipment, but these modifications will do nothing to reduce exposure via volatility.
Industry projections for 2018 suggest planted acres of dicamba-resistant varieties could be double the acres planted last year. Concerns about how the technology will be used and the possible implications of large-scale damage to non-target vegetation in 2018 remain at the forefront of countless conversations. The continued availability of this technology on soybean beyond the November 2018 label expiration date likely will be determined this growing season. Frankly, how dicamba is managed on soybean in 2018 could also impact the continued use of dicamba on other crops in the future. Much is at stake.
Last November, an ad-hoc committee from the Weed Science Society of America received a request from the EPA to offer suggestions for what success or failure for dicamba might look like in 2018. Weed scientists from soybean-producing regions offered many thoughtful comments, but for brevity I include only the response I submitted:
Success: The use of dicamba as one component of an integrated weed management program that emphasizes proper selection and application of effective soil-residual herbicides and only EARLY postemergence applications of dicamba (i.e., ~14 days after planting) followed by implementation of other herbicide or non-herbicide tactics to ensure zero weed seed production.
Failure: The singular use of dicamba as a postemergence herbicide in dicamba-resistant soybean.
Keep in mind the reason for investing in any weed management technology is to adequately control competing vegetation so the crop can express its full genetic yield potential. Merely measuring “success” in terms of reducing the number of official dicamba complaints or reports of damage to off-target vegetation diminishes the value of utilizing this technology for weed management.
Every herbicide application must follow all label directions and minimize off-target movement of spray particles. It is the absolute responsibility of the applicator, whether private or commercial, to follow all label directions before, during, and after the application of dicamba. Undoubtedly, there will be instances in 2018 when commercial applicators will have to refuse to spray if prevailing conditions are in violation of the label. Conditions that would prevent a commercial applicator from spraying also would prevent spraying by private applicators. Clearly, it is in the best interest of maintaining the availability of this technology not to spray when prevailing conditions would result in an off-labeled application.
Previously, we offered precautions for use of dicamba in dicamba-resistant soybean. Label guidelines and restrictions are meant to reduce physical movement of spray particles during application, but volatility is not prevented by label language. Registrants have publically stated the approved dicamba formulations are not no-volatility formulations, and recently generated university data would support that statement. Volatility is largely driven by temperature, so utilizing dicamba earlier in the season when temperatures are cooler could help reduce off-target movement via volatility.
Herein, we offer the following suggestions to promote successful weed management in dicamba-resistant soybean.
Steps for Successful Weed Management in Dicamba-Resistant Soybean
Plant dicamba soybean seed into a weed-free seedbed
Achieve a weed-free seedbed through the use of:
1) Preplant tillage
2) Effective burndown herbicide(s)
3) A combination of tillage and burndown herbicides
Select and apply within 7 days of planting a soil-residual herbicide that targets your most problematic weed species. If desired (and labeled), add dicamba and an appropriate buffer.
For waterhemp or Palmer amaranth, select a product containing the active ingredients from one of the following categories of control:
*Excellent: greatest efficacy on Amaranthus species and longest residual control
Good: good efficacy on Amaranthus species, residual control generally not as long
Acceptable: stronger on grass species but with some activity on Amaranthus species
Scout fields 14 days after planting. Apply dicamba at 0.5 lb ae/acre when weeds are less than 3 inches tall and when conditions allow for the application. Consider adding an approved soil-residual herbicide to the tank mix.
Scout treated fields 7 days after the dicamba application. If control is not complete or another flush of weeds has emerged, consider using non-dicamba options for complete control. Examples include alternative herbicides, cultivation, and hand rogueing. The goal should be zero weed seed production.