Illinois soybean producers are facing heightened pressure from red crown rot (RCR), a soilborne fungal disease caused by Calonectria ilicicola, which is becoming more entrenched in the state's fields. Since its Midwest emergence in 2018, the disease's footprint has steadily grown, with Illinois now seeing the most significant impact among major soybean states.

According to the Crop Protection Network, red crown rot has been confirmed in 34 Illinois counties, making it the state with the highest recorded case count. Neighboring states Indiana, Missouri, and Kentucky have also reported positive detections, as have Louisiana, Delaware, and-this year for the first time-Ohio.

"The footprint of red crown rot is expanding throughout the area-not an epidemic, but more is being found," said Syngenta agronomist Phil Krieg, who monitors southern Illinois. He added that RCR is showing up right on schedule in high-risk areas, reflecting its establishment in the soil profile.

Recognizing and Responding to Red Crown Rot

Matt Montgomery, agronomy education lead at Beck's Hybrids, emphasized the importance of field-level identification. While Sudden Death Syndrome (SDS) presents with uniform damage, RCR appears more erratically-a "mishmash" of green, yellow, and brown plants, often adjacent to each other.

To confirm RCR, growers should check lower stems for red discoloration and red fruiting bodies (parathecia) about an inch above or below the soil line, most visible in mid-August. Diagnostic lab testing is recommended to distinguish RCR from similar diseases like brown stem rot (BSR).

"Saltro is the best seed treatment on the market for RCR, but under heavy pressure, it's not always sufficient," Montgomery cautioned. With no in-season cure, management relies on prevention, weed control, and rotation, though the fungus's resilient sclerotia can persist in soil for years.

He also advised farmers to limit field spread by tackling known RCR fields last when conducting tillage or harvest: "Let's work that piece of ground last."

Weather Stress Compounds Disease Impact

The disease's growth is being compounded by adverse weather. Southern Illinois is facing prolonged dry, hot spells. According to the U.S. Drought Monitor, 4% of Illinois is experiencing moderate drought and 22% is classified as abnormally dry.

"Overall soybeans look good, finally, but dry and hot weather is taking yield away every day," Krieg noted.

Crop Progress Report Signals Mixed Outlook

The USDA Crop Progress report as of August 17 shows:

94% of soybeans in Illinois had bloomed, slightly behind the five-year average.

87% had reached the pod-setting stage, slightly ahead of historical trends.

Crop condition ratings for Illinois soybeans are:

17% excellent

43% good

27% fair

9% poor

4% very poor

These figures trail the national average and reflect ongoing weather and disease pressures.

LoTerm Implications

With red crown rot now established across much of Illinois, experts stress that loterm agronomic planning is crucial. Crop rotation, seed treatment, and aggressive weed and field hygiene practices will be essential as farmers prepare for future seasons.

"Once it's in the soil, it's not going away," Montgomery warned. "This is going to be a disease we have to manage every year."