By Daren S Mueller
Red crown rot (RCR) of soybean has NOT yet been found in Iowa, but it has cropped up in several neighboring states. RCR is fairly widespread across Illinois and has been identified in Missouri, Wisconsin, and Minnesota (Fig 1). It is likely only a matter of time before RCR is identified in Iowa.
Red crown rot can cause substantial soybean losses, and we are asking farmers and agronomist to be on the lookout for RCR in Iowa fields. To help facilitate this, the Iowa Soybean Association, through the soybean checkoff, is offering free RCR testing for Iowa farmers when samples are sent to the ISU Plant and Insect Diagnostic Clinic.
Red crown rot in a soybean field looks very similar to sudden death syndrome (SDS). Soybean leaves turn yellow and brown between leaf veins and patches of yellowing plants can be viewed from the edge of the field or from overhead (Figs 2 and 3). Leaves eventually wilt and plants may die. However, RCR causes characteristic red discoloration of the lower soybean stem (Fig 4). The fungus that causes RCR can also produce tiny, round, and red fungal structures on the stem and roots near the soil line (Fig 5). Plants with RCR may have extensive root rot (Fig 6).
Source : iastate.edu