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Update from the Field: Strange Soybean Symptoms

Posted By Dave Dyson, Agronomist on September 02, 2021

As an agronomist for The Andersons, I travel a wide swath throughout the Corn Belt. Lately, I have been noticing strange colors in the soybean fields. I have never found scouting fields at 55 mph yield good intel I have gotten out of the truck and into the fields to determine if the soybeans are injured by herbicide, a lack of nutrients, or a pest.

This time of year, the soybean plant should be around the R5-R6 growth stage. At this stage, plants should be a dark green color and be at least chest high in height. When herbicides move off target and land on a non-tolerant plant, new growth will be affected. The affected growth can be a tell-tale sign of what herbicide moved off target. Most of the soybean damage I'm seeing these days is from two growth regulators, dicamba or 2,4-D. Dicamba presents as puckered leaves on the upper part of the plant, Figure1. 2,4-D presents as elongated leaves on the upper part of the plant, Figure2.

Figure 1: This picture taken near Walton, Indiana, in 2020 shows the upper most leaves puckering due to dicamba injury.

Figure 2: This picture taken by Kokomo, Indiana, in 2020 shows the newest leaves elongated due to 2,4-D damage.

Typically, late summer is the driest part of the growing season. Nutrient deficiencies will always show up in plant leaves during a dry spell. Potassium is mobile in the plant but requires moisture to move. When potassium is deficient, it will move from the older leaves to the younger leaves. Potassium deficiencies present as yellowing, reddening, and dying leaf margins on lower leaves during the vegetative stage and on upper leaves during grain fill, Figure 3. Manganese is immobile so the deficiency will show in the younger or upper leaves. The younger leaves will present as yellowish-grey or reddish-grey with green veins, Figure 4. If the soybean plant is at R5 or younger, adding Over Pass® 10-2-10 or Korrect® can add yield to this year's crop. Nutrient needs spike around the R4-R5 growth stage to support pod fill in soybeans, Figure 5.

Figure 3: This picture taken near Gilead, Indiana, in 2021 shows yellowing on the edge of the newest leaves during grain fill. This is representative of typical potassium deficiency.

Figure 4: This picture taken by Macy, Indiana, in 2021 shows interveinal yellowing with green veins on the upper leaves. This demonstrates typical manganese deficiency.

Figure 5: This graph demonstrates the nutrient needs of soybeans during various growth stages. The curve is greatest around the R4-R5 growth stages to support pod fill.

Sudden death syndrome (SDS) is a fungal pest caused by Fusarium virguliforme. This fungus lives in the soil and can colonize the roots of the soybean plant. The effected plants start showing symptoms in mid-to-late August. The leaves present as yellow spots coalescing to form chlorotic blotches between the leaf veins, Figure 6. The above-ground symptoms are caused by toxins produced by the fungus and translocated throughout the plant. The necrotic leaves tend to twist, curl, and fall from the plant. Studies have shown the fungus lives on the residue, so reducing the infected residue will help reduce the population of the fungi. We could promote and encourage deep tillage, but for those producers in a no-till cropping system that is a non-starter. Deep tillage can also increase compaction and erosion, two yield-limiting factors that high yield soybean producers.

Figure 6: This picture taken by Waterloo, Indiana, shows the effects of sudden death syndrome (SDS) on soybeans.

The Andersons have a product, Bio Reverse®, to rapidly decompose the previous crop’s residue through the introduction of microorganisms immediately following harvest. When you apply 1pt/ac of Bio Reverse with your fall herbicide application, you will be introducing 300 billion colony forming units (CFUs), four species of bacteria, and one variety of residue-busting yeast. Reducing residue and winter annual weeds is the one-two punch that can deliver higher yields next year.Soybean cyst nematodes (SCN), Figure 7, will increase the chances of soybeans being affected by SDS. If you believe you may have a presence of SCN right now, consult your local Ag Advisor so they may begin pulling soil samples to confirm. A soybean seed treatment next spring combined with a fall application of Bio Reverse may help reduce the SCN population and thereby, decrease the chance for sudden death syndrome.

Figure 7: This picture was taken by Oakley, Michigan. In this situation, the soybean cyst nematodes (SCN) killed the soybeans outright.

In conclusion, getting out of the truck and determining what is causing the crop to look odd can give you a leg up this year and next. Herbicide drift can be devastating, but it is contained in this year's crop. Adding Bio Reverse this fall to crop residue will decrease disease and increase seed-to soil-contact for next year's planting. Adding a seed treatment to next crop's seed will reduce soybean cyst nematode population. If you need help with determining what the different symptoms are out in your soybean fields, contact your local trusted Ag Advisor from The Andersons.  

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David Dyson

Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com

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