Red Crown Rot Confirmed in Iowa

It was only a matter of time before this article needed to be written. Yesterday, we scouted a field in Des Moines County in southeast Iowa. The short story: red crown rot (RCR) was identified in a swath stretching across part of the field. In talking with the farmer, he noted that the same area had shown up on the yield monitor map two years ago, but he assumed it was sudden death syndrome (SDS).

This is a reminder that if you suspect you have RCR, please send samples to the ISU Plant and Insect Diagnostic Clinic for confirmation. There will be no charge for testing, thanks to support from the soybean checkoff. We will also be conducting a survey, similar to what we have done the past two years, to determine whether RCR is present in other Iowa fields. The current locations where RCR has been confirmed are available on the Crop Protection Network’s Red Crown Rot map. 

From an identification standpoint, RCR can look like a patch of yellow in a field when viewed from the road, like SDS. Leaves turn yellowish and brown between the leaf veins of infected plants. However, if you look below the canopy, plants with RCR can show reddish discoloration on the stem near the soil line (Figure 1). Another distinguishing characteristic is that tiny, red fungal growths, about the size of a pinhead, may also be observed under certain conditions (Figure 2). See this Crop Protection Network article for more details on disease identification, yield loss information, and disease cycle. 

For this season, there is nothing to be done from a management standpoint. However, confirming that your “SDS patches” are actually SDS will be important for making management decisions in future years.

Researchers from states where RCR is already established are currently determining best management practices as this is still a relatively new disease in the Midwest, including potential seed treatments, genetics, and cultural practices. We will share management information as it becomes available.