In-Season Management Guide 2025

Summer 2025

michigan soybean on-Farm Research in-season management guide

The information in this publication is the result of checkoff investments in soybean research.

We hope you find this information valuable and wish you a successful 2025 soybean crop.

Table of contents Biologicals on Soybeans Managing Herbicide Resistant Weeds Stay Ahead of White Mold

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From our Research Director It would be great to know which challenges our soybean crop will face this season.

However in most cases we end up reacting to stresses and doing our best to correct issues that arise such as nematodes, insects, diseases and weeds. While some crop pests are surprises, there are some that we can count on seeing each year. Two examples of those recurrent pests are included in this publication: white mold and herbicide resistant weeds. We appreciate the consistent research efforts and expertise shared by Drs. Christy Sprague and Marty Chilvers as their work aims to protect soybean yields from these pests. Likewise, Dr. Eric Anderson authored an article that shares research experience with a variety of biological products.

Please keep your input flowing to your soybean checkoff so that our funded research is meeting your needs.

From our Research subcommittee As farmer directors of the soybean checkoff, we are constantly looking for opportunities to support Michigan soybean growers. One important investment of checkoff funds is in production research. We are fortunate to have great soybean researchers who are investigating topics which are critical to soybean productivity and profitability. This publication includes some examples of our investment in research. As the research results develop, we try to make some of the projects available for farmers to try on their own farms as part of our annual on-farm research trials.

We look forward to more research results as this year’s crop and trials progress. Please stay in touch with your Michigan Soybean Committee directors and staff with comments, suggestions or questions to help guide future research.

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Soybean sidekicks: Microbes to the rescue (sometimes)

ERIC ANDERSON

MSU EXTENSION STATEWIDE SOYBEAN EDUCATOR

Agricultural biological products Table 1. Biological product results in Michigan Soybean On-Farm Research trials from 2011-2024. were a $17 billion market in 2024 and Product Year Stage Rate Number of Average yield Average income are projected to increase by nearly 14 applied (oz/ac) Locations increase (bu/ac) difference ($/ac) percent annually through the rest of this 2011-2014 V2-R1 4 17 1.8 $6 decade according to one report. A 2024 Ratchet a,b c,d farmer survey, “Biologicals: Row-Crop 2012-2014 V4-R3 1 11 0.1 -$22 ProAct Farmer Value, Perception and Potential” e 2013 PRE or R1 128 2 0.8 -$42 SumaGroulx found 87 percent of farmers in the U.S. f 2015 V3-5 or R1-3 128 13 0.6 -$14 Blackmax 22 are aware of the term “biologicals” g 2016 V3-V5 2 18 0.2 -$2 Radiate and 45 percent say they are currently purchasing or using them to boost yield, 2020-2021 In-furrow 16 14 0.3 -$3 Nutrio Unlock enhance profitability and provide soil (+ Puric Prime Max in-furrow) h health benefits. If you have attended a trade show or picked up an ag magazine Stimulate i 2022-2023 V4-R1 8 17 0.1 -$5 recently, you know that, clearly, interest 2023-2024 V4-R1 32 14 -0.3 -$15 ArchiTech j in these products has grown in recent a included Optimize 400 (2011), Stratego YLD fungicide (2012, 2013); b lipo-chitooligosaccharide (LCO); c years. harpin protein; d included Stratego YLD (2012); e microbes, humic acid; f humin, carbohydrates, humic and What are biological products? The fulvic acids; g IBA (indole butyric acid), kinetin; h microbes + humic acid; i microbes; j gamma-aminobutyric word “biologicals” can actually mean acid (GABA), nutrients different things: product is strong. And, unfortunately, it could be that some • Biologicals: Living microbes that help plants grow companies may not be as forthcoming with their results as • Biostimulants: Natural extracts from microbes we would like them to be.

• Plant growth regulators: Natural hormones that Numerous factors play into whether a given product will affect plant growth produce significantly higher yields in a field in any given • Biopesticides: Natural pest control products year including weather, presence of a given stress, timing Some people use these terms differently, but in this and method of application, and possibly even variety. We article we’ll use “biologicals” to mean all of them. That said, believe the science has shown that some products have most references will be to true biologicals. the potential to increase soybean plant health and yield The Science for Success team of university soybean as shown in controlled-environment studies, and we are specialists studied numerous soybean biological seed committed to continuing to test more products in on-farm treatment products and collected over 5,000 data points trials in the future to see whether this potential can be across 101 site-years and 21 states in 2022 and 2023. realized at field-scale. If you have any products you have In 2023, they found that Bradyrhizobium - the inoculant used that have been beneficial on your farm, please let us responsible for root nodulation and nitrogen fixation know and we will consider testing them in future trials. increased yields by 1.6 bu/acre on average. Across the entire study, they found some of the other treatments produced as much as a 3 bu/acre increase over the control, but they observed this response only 25 percent of the time.

Between 2011 and 2024, several foliar-applied biologicals were tested in the Michigan Soybean On-Farm Research program (Table 1). Although treatments resulted in a significantly higher yield than the control at 6 out of 106 locations, there were no significant differences when averaged across locations and/or years for each product.

Why do university research results often differ from those presented by companies? It could be that some companies do not perform statistical analysis on yield data and show only average yields, whereas university results include statistics to show true differences apart from the “white noise” of in-field and between-farm variability. Companies 2023 Ag biologicals landscape—companies marketing one or more biomay be testing their products in fields where specific factors based crop production product. Adapted from MixingBowlhub.com. are present (or absent) and the beneficial impact of the michigan Soybean in-season management guide

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Managing Herbicide-Resistant Weeds: What Can Be Done Now? DR. CHRISTY SPRAGUE

MSU PROFESSOR AND WEED EXTENSION SPECIALIST

Every year, weed control ranks high on the list of management practices farmers wish they’d handled better.

Weather delays, poor timing, wrong herbicide choices, and the spread of tough-to-control species - especially herbicide-resistant weeds - can all throw even the bestlaid weed control plans off course. With the cool spring slowing things down this year, many farmers are just getting started on postemergence (POST) herbicide applications in soybeans. Now is a great time to think through what those applications should look like. Here are five key points to consider before heading to the field.

1. Did Your Preemergence (PRE) Herbicides Work?

Rainfall after a soil-applied PRE herbicide is crucial. This year, most PRE herbicides should have received enough rain to incorporate and help control early-emerging weeds.

But that doesn’t mean you’re done. Late-emerging weeds like waterhemp, Palmer amaranth, horseweed (marestail), eastern black nightshade, and annual grasses still need attention. So do common and giant ragweed, which don’t have any consistently effective PRE options in soybeans.

2. Watch for Herbicide-Resistant Weeds Herbicide-resistant weeds continue to be one of the biggest challenges in soybean fields. Knowing what resistant species are in your fields - and even in neighboring fields - should guide your POST herbicide strategy.

In Michigan, newly confirmed herbicide-resistant species include: • Waterhemp resistant to 2,4-D (Group 4) and glyphosate (Group 9) • Common ragweed resistant to ALS (Group 2)-inhibitors and glyphosate (Group 9) • Ryegrass resistant to ACCase (Group 1)-inhibitors Additionally, the continued spread of PPO (Group 14)-, ALS-, and glyphosateresistant waterhemp should be considered when choosing postemergence Common ragweed

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herbicide options. You can check a county-bycounty map of confirmed herbicide-resistant weed populations on the MSU Plant & Pest Diagnostics site: canr.msu.edu/ pestid/resources/ plant-and-weedidentification/map.

3. Know Your Soybean Trait System and POST Herbicide Options Your POST herbicide options depend on Waterhemp the soybean traits planted. Here’s a quick breakdown: • Liberty/Liberty Ultra (glufosinate): Can be used on LibertyLink, Enlist E3, or XtendFlex soybeans.

• Enlist One (2,4-D) or Enlist Duo: Only for Enlist E3 soybeans.

• Glyphosate: For Roundup Ready soybeans (including many stacked trait systems).

Tank-mixing Liberty and Enlist One in some cases has shown better control of waterhemp in Enlist E3 soybeans than using either herbicide alone. This will be especially important in areas where 2,4-D resistant waterhemp has been identified.

Additionally, timing matters. Apply herbicides when weeds are under four inches tall for best results.

Always check the label for: • Soybean growth stage restrictions • Seasonal maximum rates • Preharvest intervals • Crop rotation intervals For example, Liberty/Liberty Ultra must be applied before the R1 (bloom) stage, while Enlist One and Enlist Duo can be applied through R1, but not past R2 soybean. Glyphosate can be applied through soybean flowering (R2).

4. Consider Adding a Residual to POST Herbicide Applications Some of the toughest weeds - like waterhemp and Palmer amaranth - keep emerging well into July, long after your POST herbicide application window closes. To stay ahead, consider tank-mixing a Group 15 residual herbicide

with your POST application. These herbicides won’t control weeds that have already emerged, but they’ll prevent new emergence of these species.

Common Group 15 herbicide options in soybeans include: • Dual II Magnum • Warrant/Enversa • Outlook • Zidua These Group 15 tank-mixtures will also help control later emerging eastern black nightshade and annual grasses.

Group 15 POST herbicide applications may also follow a PRE application of these herbicides. This concept is called overlapping residual or a layered residual approach. This concept can be extremely helpful for weed control in earlierplanted soybeans.

A few precautions: • Be mindful of the maximum use rates. For example, the POST maximum application rate for Dual II Magnum is 2 pints/acre, and the total seasonal limit is 3.9 pints/acre.

• Watch your crop rotation plans. Group 15 herbicides have restrictions on planting wheat after soybeans.

For instance, you must wait: • 4.5 months after applying Dual II Magnum • 4 months for Outlook, Warrant, Enversa or Zidua

Ask yourself: • Did the weeds emerge after you sprayed?

• Were they already too big?

• Was spray coverage adequate?

If none of these apply, you could be dealing with herbicide resistance. Avoid spreading seeds to other fields and consider having the weeds tested. MSU Plant & Pest Diagnostics offers a screening service: canr.msu.edu/pestid/ submit-samples/herbicide-resistant-weeds-in-Michigan For more information, consult the 2025 MSU Weed Control Guide for Field Crops (E0434) at: canr.msu.edu/ weeds.

5. Scout for Weed Escapes Check your fields 10-14 days after your POST herbicide application to see how well it worked. If weeds escaped, you might still have time for an additional postemergence herbicide application - just make sure you’re still within soybean growth stage and herbicide use rate limits.

Marestail

Figure 1. Late-season waterhemp control with a Group 15 herbicide tank-mixture with Liberty + Enlist One.

Untreated

Liberty + Enlist One

Liberty + Enlist One + Group 15 michigan Soybean in-season management guide

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Stay Ahead of White Mold:

Mid-Season Management Tactics DR. MARTY CHILVERS

MSU FIELD CROPS PATHOLOGIST

White mold (also known as Sclerotinia stem rot caused by the fungus Sclerotinia sclerotiorum) is a potentially devastating disease, capable of causing significant yield losses. Symptoms of white mold often begin in August as bleached lesions on the stem, followed by fluffy mycelial growth and then the production of sclerotia (black resting bodies) on or in stems and pods. Unfortunately, at the time of visible symptom development, it’s often too late for an effective fungicide application.

Disease outbreaks of white mold occur when three key factors align: the presence of a susceptible host, field history of disease, and favorable environmental conditions, particularly cool (< 85°F), moist weather during flowering.

Sclerotia resting bodies in the soil germinate to produce apothecia which release spores that infect through flower petals. However, don’t be tricked into confusing harmless mushrooms such as the birds nest fungus with Sclerotinia apothecia. In fact, these Sclerotinia apothecia are so hard to find that they are often not a good scouting tool.

Which fields should I target for management?

Field history is one of the most important considerations.

Target fields that have a history of white mold. The sclerotia resting structures can survive for up to ten years in soil.

Although tillage can initially bury sclerotia, subsequent tillage will bring sclerotia close enough to the soil surface where they can germinate. Studies have demonstrated that long term no-till fields tend to be at lower risk to white mold. Additionally, variety susceptibility is an important component. Although no varieties are immune to white mold, variety selection can make a huge difference. It’s a good idea to look up your varieties susceptibility/resistance scores to understand where you may have greater challenges if disease favorable conditions align.

When should fungicides be applied?

The best fungicide timing is from beginning of flowering (R1) through to the beginning of pod development (R3).

Once we hit the “full pod” (R4) growth stage fungicides will not be as effective in suppressing disease. To differentiate the R3 from the R4 growth stage, start at the top of the plant and identify the first fully open leaf. Now including that node, count down four nodes and look at the size of the developing pod at the fourth node. If that pod is at or greater than 3/16” (5mm) it’s at the R3 growth stage, but once the pod is more than ¾” (2cm) it’s at the R4 growth stage and fungicides will be far less effective.

What about disease forecasting tools?

The Crop Protection Network has introduced the Crop Risk Tool, a free, web-based resource designed to help soybean growers make timely, informed decisions for managing foliar diseases. Built on years of field data and research, the tool uses local weather inputs to forecast the risk of white mold. It provides daily risk updates and a 7-day forecast to support fungicide applications during critical growth stages. The tool accounts for variations in dryland and irrigated environments and is easily accessible through the CPN website, where additional resources like fungicide efficacy tables and disease ID guides are also available. (cropprotectionnetwork.org/crop-diseaseforecasting) Figure: Top: The very common and harmless “birds nest” fungus, which is often confused with the white mold fungus. Bottom: Sclerotinia (white mold fungus) apothecia and sclerotia on soil surface (Jill Check).

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Which fungicides should be applied?

The fungicide efficacy tool hosted on the Crop Protection Network lists fungicides and their efficacy

for white mold. Fungicide products ranked as “good” for white mold suppression include Endura, Approach (in a two-pass system), Omega and Propulse. In our small plot work we also have good success with the herbicide Cobra, which often performs as well as the best fungicides under high white mold disease pressure. However, farmers should note there is the potential for burn, and some yield loss under conditions that don’t favor disease. (cropprotectionnetwork.org/ publications/fungicideefficacy-for-controlof-soybean-foliardiseases)

Figure: To differentiate the R3 and R4 growth stages, look at the size of the developing pod at the fourth node of a fully developed leaf. If that pod is 3/16” (5mm) it’s at the R3 growth stage, once the pod is mode than ¾” (2cm) it is at the R4 growth stage.

Are there other considerations?

Foliar fungicides can be an effective tool for managing white mold. However, they are only one of the tactics available and should be used in combination with other white mold management practices such as partially resistant varieties, wide rows, reduced planting rates, irrigation water management, and appropriate tillage methods. Be sure to make note of which fields develop white mold for future planning, and if you are investing in a fungicide, be sure to leave check strips to pencil out the economics.

Each year we screen varieties, test new fungicide products, biologicals and amendments. The most promising of these are brought to on-farm research trials in collaboration with the Michigan Soybean Committee and Eric Anderson, the MSU Extension Soybean Educator. If you are interested in a particular product, we would like to hear from you. Please reach out via email to chilvers@msu.edu.

Figure: The Crop Risk Tool in action looking at risk level for white mold and frogeye leaf spot across multiple fields in 2024.

michigan Soybean in-season management guide

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Summer 2025

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