A soybean disease new to Missouri could hurt crop yields this season. It’s tough to prevent, hard to detect and, as of now, there’s no cure.
Red crown rot stems from a fungus that lives in the soil, which makes it easy to accidentally spread. Its symptoms include discolored leaves and the appearance of a fungus that looks like small red balls on the stem.
“Once we introduce this fungus into a field, you cannot un-introduce it,” said Mandy Bish, a University of Missouri assistant professor and plant pathologist.
Red crown rot has been in the U.S. since the 1960s, first affecting peanuts. The first two cases of the disease on Missouri soybeans were confirmed last year, but since it mimics the symptoms of another soybean disease, sudden death syndrome, Bish said it might have been in Missouri longer than that.
“One was an organic production farm,” she 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.”
Bish said in one field, the disease caused a 52% decrease in soybean yield. Without a cure, Bish recommends farmers pursue “band-aid solutions.”
“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,” she said. “He's a seed dealer too.”
For other farmers, she recommends “rotating to a crop that is a non-host for this pathogen,” such as corn.
It’s too early to detect red crown rot on this season’s soybeans, but Bish said the disease is here to stay. Farmers should try to identify the disease as quickly as possible to prevent spreading it to other areas of the farm through their equipment.
“Trying to contain it is the number one priority,” she said. “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,” she 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.”
Farmers can send in samples of their crops to MU’s Plant Diagnostic Clinic, which now accepts digital submissions.
