Red crown rot is expected to reappear in Illinois soybean fields this season. The disease was first confirmed in Illinois in 2018 and is an emerging issue for the top soybean producing state.
Robert Bellm, a certified crop adviser with Brasse Farms Inc. in Madison County, encountered it in 2020 and continues to find it in new fields.
“We don’t know if it’s actually expanding or if people are just becoming more aware of it,” he told FarmWeek. “I expect to see it again in 2024, especially in fields that were positive in 2023. It’s like sudden death syndrome or soybean cyst nematode. Once it’s in the field it’s going to reoccur in those same fields and expand.”
Carl Bradley, a professor of plant pathology at the University of Kentucky, told FarmWeek the disease causes leaves to turn yellow and adds reddish discoloration on the lower stem and roots resulting in premature death.
He said while it is easy to mistake red crown rot for other diseases there is one symptom that is very diagnostic. “The fungus produces fruiting bodies called paresthesia,” he said. “They’re a spherical shape, reddish orange in color, and they’re going to be on the lower stems and roots. When those are present and you see all the other symptoms, you know it’s red crown rot.”
Bellm added that because the symptoms mimic other common problems like sudden death syndrome, brown stem rot, and southern stem canker, it’s important to have a hands-on scouting approach.
“You literally have to get into the field and eliminate your bias of what you think you’re going to see,” he said. “This is not a windshield survey. This is in the field, sometimes on your hands and knees, pulling up plants, looking for the signs and symptoms on the lower crown and roots and properly identifying it.”
Bellm encourages growers and agronomists to scout in the middle of July and dig up discolored plants.
“The early affected plants melt down very rapidly and disappear into the canopy,” he added. “You don’t start to see the broader areas of discoloration in the canopy until two or three weeks later. That early infection is showing up late R3 or early R4.”
Bradley said there is still a lot to learn about the disease, and while there is no silver bullet solution, they are conducting research on management options.
“The only thing that consistently suppressed disease symptoms to some degree was Saltro seed treatment, a Syngenta product,” he said. “It is currently the only product labeled for management of red crown rot.”
Bradley said in Kentucky they are seeing more red crown rot pressure in later planted soybeans, especially double crops, so they are doing more research on planting dates. He adds that the disease spreads by the movement of soil.
“So if you have it in one field and you don’t have it in others, do things to prevent moving it from one field to the next, like cleaning equipment,” he said.
Bradley and Bellm, who both spoke on a red crown rot panel during the 2024 Illinois Soybean Summit, agree that identification is key to managing the disease moving forward. They encourage Illinois growers and agronomists to submit potentially infected samples to the University of Illinois plant clinic to help track it this season.
Rhiannon Branch is the commodities editor for FarmWeekNow.
