Mich. Growers Urged to Scout Fields for Red Crown Rot
Published: Friday, August 14, 2026
Soybean growers should be on the alert for red crown rot, according to Mark Seamon, research director for Michigan Soybean Assn.
Red crown rot isn't new to the U.S., having troubled peanut growers in southern states for 40 years. In recent years, the problem has moved north and into soybean crops. Incidents of the disease sprouted in 2025 in Wisconsin, Minnesota and Ohio. Indiana first spotted the problem in 2022. While still unreported, the fast-moving disease is likely already in some Michigan fields.
The fungal disease is caused by soil-borne pathogen, Calonectria ilicicola. Symptoms resemble Soybean Sudden Death Syndrome that show up late in the season, causing interveinal chlorosis followed by necrosis of leaves, a result of the fungus releasing toxins into the plant. Red crown rot usually only affects low lying patches within a field.
Identifiers for red crown rot include tiny red fruiting bodies that carry spores accumulating on lower plant stems. Plants can be easily pulled from the soil because lateral root stems have decayed, leaving the plant with a central pencil root.
Symptoms for Sudden Death Syndrome are similar. However, infected plants will have a brown pith inside the central stem.
Red crown rot spores can survive in the soil for many years. Since this is a developing disease for Michigan growers, identification and isolation is important to manage infestations.
Seamon says that there are seed treatments that look promising to hold back the disease but that selection for resistant seed varieties will be the best path for prevention. He urges producers with suspicious plants to request a test kit to make a positive identification. Test kits can be requested at https://www.michigansoybean.org/red-crown-rot.html.
Forage yields have suffered due to a cooler than average June, and dry conditions later in the season. Kim Cassida said that not a lot can be done to correct a two-pronged set of conditions that were simply not conducive to strong forage yields.
"The best way to withstand the stress is to have a healthy stand going into the plant stress so the plants will rebound better," she said.
Because there is no Band-Aide solution, she suggests monitoring P and K levels now, and applying as needed so that forages will have a better chance of strong over wintering, and a healthy start for the next season.
Christy Sprague reported that there is some 2-4-D resistance in water hemp, and plants that are showing up should be pulled quickly before they go to seed. MSU can help identify if any weed escape found in fields is resistant.
According to Chris Difonzo, now is the time to scout for corn leaf aphids, especially in southern Michigan counties in sweet corn crops. Corn rootworm has failed to thrive this year due to unfavorable conditions. But if weather and soil conditions became favorable in another year, corn rootworm could be a significant problem because most populations are now resistant to Bt corn. Breaking the rootworm cycle through rotation is a key in prevention.
The public is invited to the Michigan Water Quality Management Forum and Field Showcase at the Kellogg Biological Station, 10461 N 40th St., Hickory Corners, Mich., on Aug. 26 from 9 a.m. to 2 p.m. Preregistration is required. The event will discuss why nutrient reduction in agriculture practices matters for Michigan water quality, and how the fundamentals of soil health can help preserve and protect Michigan waters. More information is available by contacting Sarah Zeiler at szeiler@msu.edu. Preregistration can be completed at https://pears.io/events/msuext/9285/.
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