Experts Warn of Red Crown Rot in Soybean Crops

By Blake Jackson

A new threat to Missouri soybean fields has emerged in the form of red crown rot, a difficult-to-detect and incurable disease that could significantly reduce yields this growing season.

Caused by a soil-borne fungus, the disease is easily spread and nearly impossible to eliminate once introduced.

"Once we introduce this fungus into a field, you cannot un-introduce it," explained Mandy Bish, assistant professor and plant pathologist at the University of Missouri.

Red crown rot, which first appeared in the U.S. in the 1960s affecting peanuts, was officially confirmed in Missouri soybean fields just last year. However, Bish suspects the disease may have been present longer. It closely resembles symptoms of sudden death syndrome, making it difficult to diagnose without lab testing.

"One was an organic production farm," Bish said. "The farmer was not submitting samples because he thought he had red crown rot. He was just submitting samples to our plant diagnostic clinic to see what all he had, and we happened to see these little red spheres on the roots of the plant, which are called perithecia."

In one case, the disease caused a 52% reduction in yield, highlighting its potential severity. As there is no known cure, Bish advises farmers to explore alternative management strategies.

"For the organic situation, I recommended that he test some of his organic lines in that field to see which ones hold up the most to red crown rot, because then you might have a market," Bish said. "He's a seed dealer too."

For conventional operations, rotating to non-host crops such as corn is advised.

Though symptoms may not yet be visible in this year’s soybeans, Bish warns the fungus is now established in the region. Early identification and containment are essential to reduce further spread.

"Trying to contain it is the number one priority," Bish emphasized. "So if I know I have a field with red crown rot, then I want to make sure all my equipment goes into that field last."

"But one of the issues is that the fungus, the spores, move through the air," Bish added. "So you can do the best you can on your field to manage this disease, but the spores are coming in from other places too, and that can be frustrating."

Photo Credit: istock-oticki