Red crown rot is a new disease in the Midwest, and was first detected in 2017 in a single field in Pike County, Illinois.
The fungal disease is soil-borne and causes a root/crown rot following wet conditions near planting, according to a University of Illinois Extension Field Crop Disease Hub post by Nathan Kleczewski.
Later in the season, typically after R3, the fungus can produce a toxin that moves into the foliage. Severely affected plants die or senesce prematurely, with the leaves staying attached to the plant.
The important thing to note is that there are several diseases and issues that can cause similar symptoms, so drive-by scouting is not sufficient.
Once you see interveinal chlorosis, the next step is to look for plants that are more advanced in terms of disease. Inspect the crown and stems of these plants. If conditions have been wet, you may see small round, brick red “balls” on the lower stem. You also may see the lower stem covered by white fungal growth.
The key here is the presence of fungal tissues, not simply a reddish coloration to the stem.
Researchers are working to better understand the distribution and management of red crown rot in Illinois. If you have plants with interveinal chlorosis, or suspect red crown rot, collect several lower stems and roots and place them in a cooler in a 1-gallon Ziploc bag. Keep samples in a fridge until they can be shipped, overnight Monday-Wednesday, to: Kleczewski Lab-RCR Survey. 064 NSRL, University of Illinois, 1101 W Peabody Drive, Urbana, IL 61802.
On each bag include the date, county, coordinates, percent of field affected and previous crop, as well as a contact email or number.