Summer 2024 In-Season Management Guide

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 2024 soybean crop.

Table of contents

Foliar Fungicides on Soybeans

Identifying Soybean Reproductive Growth Stages

Considering Double Crop Soybeans After Wheat This Year? 3 4 6

From our Research Director

This season has started with plenty of challenges to soybean production. While the state average planting dates were not much different than our five year average, the struggle of planting in short windows of opportunity into field conditions that were less than ideal made this planting season seem tough. Facing these ever-changing challenges while growing a high-yielding soybean crop reaffirms the need for continued production research. This publication includes some valuable information on the management of your crop and should help you to make informed production decisions during the growing season.

From our Research subcommittee

The seven farmer directors on the MSC board carefully consider the best uses of checkoff funds each year. Our research subcommittee further evaluates which production research projects best align with the strategic use of your checkoff investments. Our work included the thoughtful consideration and funding decisions for nearly 30 production research projects this year. The on-farm research program is in addition to those projects and is an example of an effort to create value for your farm by evaluating products and practices that you may be considering this year.

As always, please contact any of your MSC farmer directors or staff if you have ideas that you would like to see included in the future. Best wishes on your 2024 soybean crop.

Foliar Fungicides on Soybeans

MARK SEAMON MSC RESEARCH DIRECTOR

The use of fungicides on many field crops has increased in the past 10 to 15 years across the country. The agricultural chemical industry has offered several fungicide options for the control of leaf diseases in soybeans. These products offer control of diseases such as Septoria brown spot and Frogeye leaf spot. Other diseases seen in Michigan soybeans include white mold, sudden death syndrome (SDS), Phytophthora stem and root rot, Cercospora leaf blight, Rhizoctonia root rot and downy mildew. It is critical that you know which disease is most likely in your soybean field and to use multiple control options including variety selection, crop rotation, row spacing, seeding rate and fungicides.

The Michigan Soybean On-Farm Research program has responded to the interest of growers to evaluate the yield and economics of using foliar fungicides across 55 farms over six years. This evaluation has included several commercially-available fungicides at multiple sites. Trial results are listed below.

Fungicide: Stratego® YLD

Trial years: 2012 and 2013

Number of trials: 9

Yield Effect: Increased yield by 1.4 bushels per acre

Fungicide: Priaxor®

Trial years: 2014 and 2015

Number of trials: 22

Yield Effect: Increased yield by 2.1 bushels per acre

Fungicide: Miravis® Neo

Trial year: 2020

Number of trials: 14

Yield Effect: Increased yield by 2.0 bushels per acre

Fungicide: Delaro® Complete

Trial year: 2023

Number of trials: 10

Yield Effect: Increased yield by 3.0 bushels per acre

Although the above results show a consistent average yield increase from the use of foliar fungicides, there was variability each year with fields that showed no yield response and others that responded with increased yield. Therefore, it is logical to make fungicide application decisions for each field by your judgment of the potential for disease using field history of disease, density of soybean canopy, variety disease ratings, crop growth stage and cost. MSC continues to invest checkoff funds to evaluate fungicides in on-farm trials and with Dr. Marty Chilvers at MSU in-state as well as collaborative sites across the Midwest with university pathologists in the Crop Protection Network cropprotectionnetwork. s3.amazonaws.com/soybean-foliar-efficacy-2024.pdf

Frogeye leaf spot

Septoria brown spot

identifying soybean reproductive growth stages

ERIC ANDERSON

MSU EXTENSION SOYBEAN

EDUCATOR

JENNA FALOR

MSU EXTENSION FIELD CROPS EDUCATOR

Knowing the growth stage of a soybean crop is critical as several management practices and pesticide restrictions are based on crop stage. Use this summary to refresh your memory on how to identify reproductive growth stages and the key management practices associated with each stage. Note: a field is considered to have reached a given stage when at least 50 percent of plants exhibit the primary characteristic for that stage.

All growth stage photos are Copyright Iowa State University Extension. Thank you to them for allowing us to use the photos in this report.

R1 - Beginning flower

Characteristics:

One flower on any node on the main stem, typically starting on nodes 3-6 and progressing upward and downward; rapid vertical root growth begins; new flowers form until early R5 Management:

• Apply white mold fungicide to protect flowers.

• Scout for soybean aphids (refer to MSU-OSU Field Crops Insect Guide for considerations and thresholds).

• R1 is the last stage to apply dicamba products on Xtend soybeans.

• Glufosinate on LibertyLink beans must be applied prior to R1.

• To reduce the risk of white mold, irrigation during R1–R2 is not advised unless necessary.

R2 - full flowering

Characteristics:

One open flower on one of the two uppermost nodes with a fully developed leaf (unfurled, edges no longer touching) on the main stem; pods beginning to form on lower nodes; plants have achieved ~50% of full height and 25% of final dry weight Management:

• Apply white mold fungicide if not previously applied.

• R2 is the last stage to apply glyphosate (refer to MSU Weed Guide for questions on individual products).

• Conduct mid-season tissue sampling to monitor nutrient status by collecting topmost fully developed trifoliate from several plants, minus the petiole.

• Continue scouting for insect damage.

R3 - beginning pod

Characteristics:

One pod 3/16-inch on any of the four uppermost nodes with a fully developed leaf on the main stem; number of pods determined R3-R4 Management:

• Scout for diseases and insect feeding and apply pesticide if needed (refer to the Fungicide Efficacy Chart from Crop Protection Network for pre-harvest interval restrictions).

• Begin irrigating. The crop experiences peak water use R3–R6.

R4 - full pod

Characteristics:

One pod 3/4-inch on any of the four uppermost nodes with a fully developed leaf on the main stem; stress from R4–R6 will result in the most yield loss

Management:

• Continue scouting for insects and diseases.

R6 - full seed

Characteristics:

R5 - beginning seed

Characteristics:

Seed is 1/8-inch on any of the four uppermost nodes with a fully developed leaf on the main stem; plants attain maximum height, node number and leaf area; nodulation is maximized at R5.5, after which nodules begin to die; seed size is determined during R5.5–6.5

Management:

• R5 is the last stage to spray for soybean aphid if necessary.

• Continue scouting for insects and diseases.

Green seeds fill pod cavity on any of the four uppermost nodes with a fully developed leaf on the main stem; pod weight peaks; most nutrients taken up by R6.5; leaves on lower nodes begin yellowing; protective membrane pulls away from seed at end of R6, analogous to black layer in corn, signifying physiological maturity

Management:

• R6 is the last stage to spray for soybean aphid if necessary.

R7 - beginning maturity

Characteristics:

• Continue scouting for insects and diseases.

One pod anywhere on the plant has reached mature pod color; seed dry matter peaks; leaf yellowing increases and may begin dropping by the end of this stage; seeds at 60% moisture; frost injury from this point forward will have minimal impact on yield

Management:

• Cease irrigating when 50% of leaves have turned yellow.

• Scout for green stem, lodging and other issues that could impact harvest.

R8 - full maturity

Characteristics:

95% of pods have reached mature color

Management:

• Once R8 is reached, harvest can typically occur after 5–10 days of good drying weather.

• Begin harvest at 13–15% moisture.

• If stems are green, delay harvest if possible.

• Consider collecting soil samples for soybean cyst nematode (SCN) and utilize testing paid for by the Michigan Soybean Committee.

considering double crop soybeans after winter wheat this year?

ERIC ANDERSON MSU EXTENSION SOYBEAN EDUCATOR

Winter wheat crop development is currently ahead of normal, opening a larger window for double-crop soybeans. Table 1 shows current wheat growing degree day (GDD) accumulation through May 20, 2024. It also shows the 10-year average and departure from normal. Across these locations, wheat is about 9-11 days ahead of normal. If this weather pattern continues, wheat harvest could start a week or more earlier than normal this year.

DENNIS PENNINGTON

MSU EXTENSION WHEAT SPECIALIST

coming one week later on average. The USDA’s Risk Management Agency expanded eligibility for federal crop insurance for double-crop soybean production following wheat in 58 counties in Michigan beginning in 2023 through a written agreement with no history of double-cropping (Fig. 1). Double-crop soybean yields range from 0 to 30 bushels per acre.

Table 1. Wheat GDD (base 0) accumulations since January 1, 2024 for selected Enviroweather stations.

Two critical questions must be answered when considering double-crop soybeans: Is there enough soil moisture left after wheat harvest? And is there enough time to raise a soybean crop before a killing frost?

9 Cassopolis (GLBRC) 960 743 217 29% 11

Planting double-crop soybeans in Michigan has historically been a high-risk venture due to the limited growing season following winter wheat harvest. However, the climatic trend over the past several decades has been a longer growing season with the first hard freeze

Figure 1. Map of federal crop insurance eligibility for double-crop soybeans following wheat. Adapted from USDA-RMA 2023.

Maintaining soil moisture through wheat grain fill via rainfall or irrigation is important not only to optimize wheat yield but also to ensure enough moisture for germinating soybean seed. Both surface and subsurface moisture levels are important. If there is not enough moisture near the surface to germinate the seed, critical time and yield potential will be lost. If the subsoil is dry, the soybeans will be entirely dependent on rainfall for the remainder of the season resulting in a risky venture. As the old adage goes for double-cropping, “If June is dry, do not try.”

Assuming adequate moisture is available, addressing the “enough time” question is multi-faceted and includes management decisions in several areas.

Wheat Harvest Timing

Although wheat is typically harvested at 13–15% moisture for sale or storage, grain yield and quality will not be decreased when harvesting at 20-22% moisture. The obvious advantage is being able to plant 7–10 days earlier. A study in Kentucky found harvesting wheat at 20–22% followed by immediate soybean planting resulted in an 8–12 bu/ac soybean yield increase compared with harvesting wheat at 13–15% moisture. Although glyphosate can be used as a pre-harvest aid in wheat, it is unlikely to significantly enhance wheat dry-down. The disadvantage of harvesting wheat early will be the added cost of drying or dockage.

Wheat Straw

One approach to managing wheat residue is to cut wheat at 8–12” and ensure the combine distributes the chaff the entire width of the head. Growers can plant immediately following harvest with a no-till drill with discs that effectively cut through the residue down to planting depth. This has the added advantage of conserving existing soil moisture by avoiding tillage. If available, using a stripper

header will minimize residue on the ground. Taller wheat stubble will also help force soybeans to set pods higher off the ground, minimizing harvest losses due to missed pods. Another approach is to cut and bale the straw prior to soybean planting. In addition to the extra revenue stream, the advantage here is in decreasing residue cover and increasing the chances of good seed-to-soil contact by avoiding “hair-pinning” of the straw in the furrow. The disadvantage is the delay in getting soybeans planted, but if this operation can begin the same day as wheat harvest, the planting delay may be minimal.

Soybean Planting

All of the same decisions that need to be made when planting soybeans in May need to be made when planting in July, with a few caveats. Conventional wisdom says plant by July 10th for a profitable crop, although this is largely weather-dependent. A rough rule of thumb is that 1 bu/ac/ day is lost with delayed planting in July. With roughly 60 fewer days of the growing season ahead compared with a normal planting, changes must be made with respect to variety selection, seeding rate, row spacing and more.

• Select a medium to long maturity group (see Fig. 2) to maximize yield. Selecting an ultra-earlymaturing variety, although increasing the odds of reaching maturity before freezing, has consistently resulted in lower yields. However, a frost event prior to maturity will result in green plants at harvest. Ask your seed dealer about varieties that will yield well under double-crop.

• Stand count at harvest should be above 180K, so aim for a seeding rate of 200K–225K.

• In order to quicken canopy closure and maximize sunlight capture, use a narrow row spacing, ideally 15 inches or less. This will also help with weed control during late-summer.

Weed Control

Choose fields for double-cropping where weeds were adequately controlled with spring herbicide applications in wheat. However, be aware that some wheat herbicides have rotational restrictions for soybean (e.g. Huskie - 4 months, Talinor - 10 months). Refer to Table 12 in the 2024 MSU Weed Control Guide for Field Crops for rotation restrictions for several common herbicides. Once wheat is harvested, weeds will typically grow rapidly as sunlight becomes more available. Depending on weed pressure and which species are present, these weeds may need to be controlled before soybean planting or emergence. Volunteer wheat will also likely need to be controlled, so consider making a postemergence application after volunteer wheat has emerged and other weeds have outgrown injury from the wheat harvest. Remember, growing weeds (and volunteer wheat) will use up soil moisture, so timely control will be critical.

For those not planting a non-GMO soybean variety, selecting a herbicide-tolerant variety will provide more options for a double-crop weed control program. In-crop dicamba applications in Xtend soybeans are not allowed after June 30, so consider selecting Enlist E3, LibertyLink,

or other traits besides Roundup Ready, particularly in fields with known glyphosate-resistant weeds. For example, 2,4-D choline, glyphosate and glufosinate can be safely used on Enlist E3 soybean with no calendar date restriction. Do not use herbicides that will injure soybean (e.g. Cobra, Flexstar, Blazer) as yield will be impacted in this shorter-season crop. Also, consider including a residual herbicide to keep fields weed-free until canopy closure, particularly if later-emerging weeds like pigweeds or waterhemp are present.

Other considerations when considering double-crop soybeans following wheat:

• Select fields with few stones or consider rolling fields after planting to reduce potential for cutter bar damage when harvesting shorter plants.

• Avoid planting double-crop soybeans in fields infested with soybean cyst nematodes (SCN) as the shortened time between soybean crops will increase SCN populations.

• Scout for soybean aphids. If aphid populations are high in earlier-planted soybeans, consider including an effective seed treatment (e.g. Gaucho, Cruiser) which would protect double-crop soybeans for 2-4 weeks as aphids move from earlier-planted fields to doublecrop fields. However, if aphids have reached threshold, a well-timed foliar application may provide more protection than a seed treatment. Aphids reproduce faster in late-planted soybeans and can cause more injury because the plants have less leaf area and root growth than soybeans planted earlier in the season.

Planting double-crop soybeans is risky in Michigan, but following the guidelines above can help reduce that risk. Also, be aware that this practice will add another soybean crop to your rotation. This can decrease future soybean yields by promoting higher levels of soil-borne diseases and soybean cyst nematodes.

Figure 2. Soybean maturity zones in Michigan.