Red Crown Rot of Soybean

Figure 1. Foliar Symptoms

Red crown rot (RCR) is a soybean disease caused by the soilborne fungus Calonectria ilicicola that is spreading to parts of the Midwest. There have been no confirmed reports of RCR in Ohio, but it has been detected in Kentucky and Illinois.  RCR can be easily confused with other soybean diseases that cause similar foliar symptoms.

RCR can be misidentified as sudden death syndrome (SDS) or brown stem rot (BSR) as all three diseases can cause yellowing between the leaf veins or interveinal leaf chlorosis (Figure 1.)

Figure 2. Stem discoloration

Proper diagnosis will require digging up the plant, scraping the soil off, and inspecting for red discoloration on the outer stem (Figure 2). Also look for small, brick red perithecia (fungal sexual structure) on the lower stem or root crown area. These perithecia will be smaller than the tip of a pencil and more likely to be observed following wet weather.

In general, concentrate scouting efforts for RCR in low-lying, saturated areas of the field between the R3 (beginning pod) and R5 (beginning seed) growth stages. Keep an eye out for scattered patches of plants dying off early.

If you have questionable areas in your beans and suspect RCR or sudden death let me know.  I can collect plant samples and send them to our lab for diagnosis.

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