Red Crown Rot Confirmed in Ohio Soybean Field for the First Time

For the first time, Red Crown Rot (RCR) has been confirmed in Ohio soybean. The disease was found in a Delaware County field after the grower and crop consultants submitted symptomatic plants to the Ohio State Soybean Pathology and Nematology Laboratory. Laboratory analysis confirmed the presence of Calonectria ilicicola, the fungus that causes RCR. Now that it has been found, RCR may be in other parts of Ohio, therefore scouting and proper identification become paramount.

Looks Like SDS – But It’s Not

RCR (Fig. 1) can be easily mistaken for sudden death syndrome (SDS) because both cause yellowing and browning between leaf veins during pod fill. But there are important differences that help separate the two:

• RCR: Reddish discoloration develops at the base of the stem (crown), often with tiny red fungal structures at the soil line. Plants can die quickly, and dead plants usually retain their leaves attached to stems.
• SDS: The stem surface generally looks healthy, and roots often show blue fungal growth. Plants affected by SDS often undergo premature defoliation, dropping leaves early while the petioles remain attached.

From above the canopy, RCR and SDS look nearly identical. That’s why digging plants (not pulling), checking the crown, and sending samples to a diagnostic lab are essential for correct identification.

Figure 1. Symptoms of red crown rot (RCR) observed for the first time in Ohio (Delaware County, August 2025). Top row (left to right): field with widespread interveinal chlorosis and necrosis during pod fill; close-up of leaf showing interveinal browning; soybean plants killed prematurely with leaves still attached. Bottom row (left to right): external root and crown discoloration; reddish discoloration in lower stem tissue; red reproductive structures (perithecia) of the fungus at the base of the stem near the soil line.

Conditions That Favor Red Crown Rot

RCR develops most severely in warm, wet soils, particularly when soil temperatures are between 77 and 86°F (25–30°C), the range in which the fungus actively infects soybean roots. This means that the planting date and associated soil temperatures can influence disease severity. The pathogen thrives in sandy or lighter-textured soils and in areas with poor drainage or standing water. RCR is especially challenging because it can survive in soil for many years, even without soybean, allowing it to persist and infect future crops. Fields with a history of soybean or other susceptible legumes, such as clovers, vetch, or lupine, are at higher risk.

Why Does It Matter?

In states where RCR is established, yield losses can be significant under favorable conditions. Because it is soilborne and infects several legumes, the pathogen cannot be eradicated once present. Early detection and tracking are critical to develop Ohio-specific management strategies and protect soybean yields.

Management of Red Crown Rot

No soybean varieties in the U.S. have complete resistance, but some show partial tolerance. Management focuses on reducing disease severity and slowing spread:

• Crop Rotation: Avoid planting soybean or other legume hosts (e.g., red, white, and crimson clover, vetch, lupine, alfalfa, peanut) for at least two years in infested fields. Rotation to non-host crops such as corn or small grains can reduce inoculum, but may not eliminate it.
• Variety Selection: Choose varieties with the best available partial resistance/tolerance where possible.
• Planting Date: Avoid planting soybean early when soil temperatures are already warm and wet, as this favors early infection and more severe disease.
• Drainage Management: Improve field drainage where possible to reduce periods of soil saturation.
• Fungicide Seed Treatments: Some seed-applied fungicides may suppress early infection, but need be combined with other practices.
• Equipment Sanitation: Prevent soil movement from infested to clean fields by cleaning tillage and harvest equipment.

Once established, management is long-term and preventative, aiming to protect yield potential.

What to Do if You Suspect RCR

1. Scout fields during pod fill, especially if you see yellowing leaves in patches (Figure 1, upper left).  August and September are the optimal months for scouting, as RCR develops progressively over time. Weekly scouting is recommended during this period to monitor symptom progression effectively.
2. Dig plants (do not pull) and check for reddish crown discoloration.
3. Place plants in a plastic zip-top bag, removing as much air as possible to reduce moisture loss. Include field details (county, variety, planting date, recent weather).
4. Submit samples to one of the following:

• Soybean Pathology & Nematology Laboratory
  110 Kottman Hall, 2021 Coffey Rd, Columbus, OH 43210
• C. Wayne Ellett Plant and Pest Diagnostic Clinic 
  234 Selby Hall, 1680 Madison Avenue, Wooster, OH 44691

Submitting Samples for Red Crown Rot Diagnosis

With support from the Ohio Soybean Council, our lab will process samples to confirm RCR. Please complete this submission form.

More details on sample collection can be found here: Collecting Soybean Samples for Disease Diagnostics (OSU PDF)

LEARN MORE: For detailed information on disease biology, symptoms, management, and distribution visit the Crop Protection Network’s Red Crown Rot Map and Red Crown Rot: Understanding its Impact and How to Manage it.