Red crown rot, a fungal disease historically prevalent in the southern U.S., is now spreading to the Midwest, causing stem and root deterioration along with significant yield loss.

Caused by a pathogen first identified in 1950, it has affected soybeans in the southern U.S. since the 1970s, also impacting crops like peanuts, ginger and blueberries. In recent years, the disease has been found in Kentucky, Indiana, Illinois and, most recently, Missouri.

Red crown rot thrives in wet, poorly drained fields with warm conditions accelerating its spread. Secondary infection occurs through spores dispersed by rainfall, while late-season infections cause toxin buildup in leaves, mimicking sudden death syndrome (SDS). The fungus can overwinter, persisting for years and spreading through plant debris, soil movement, equipment or livestock.

The key identifying feature is the presence of tiny red round-shaped fruiting bodies known as perithecia on the crown and roots near the soil line. Under wet conditions, the fungus may extend above the soil line. Additional signs include white fungal infected tissue and gray discoloration in the pith. Severely affected plants may be easily pulled from the soil and could have multiple pathogens.

Symptoms typically appear after the R3 stage of soybeans, with initial yellowing of leaves. Root and stem rot can occur without foliar symptoms. Even though red crown rot infection can occur early in the development of the plant, the symptoms may not be easily recognized until later.

“The symptoms are likely there, but you may not find them unless you’re really looking for them,” said Dr. Carl Bradley, professor and Extension plant pathologist at the University of Kentucky in a Pioneer Forward-thinking Farming Webinar. “With this pathogen, it is really aggressive. It is one of the most aggressive root-rotting pathogens that I’m aware of in soybeans, and by the end of the season, you really just don’t have anything.”

Yield losses of 30% have been recorded in Louisiana and Mississippi. Since no rescue treatments are available, proactive management is necessary. Management strategies include planting later in infested fields, improving soil drainage and controlling root-feeding insects and nematodes. Additionally, crop rotation to non-host crops can help reduce soil inoculum.

Source - https://www.croplife.com