An Old Disease Makes A Return Appearance: Late Season Diseases

Anne Dorrance, Harold Watters, CPAg/CCA

Stem Canker (Left) and Phytophthora Stem Rot (Right)

Stem canker has been identified in a few fields in Ohio as well as neighboring states this year.  The key symptom is a dieback of the plant.  A canker can be found, for northern stem canker at the 3rd to 4th node.  It is reddish brown and can surround the stem or go up as a streak along one side of the plant.  This can be separated from Phytophthora stem canker as in Phytophthora the base of the plant and roots are decayed while in stem canker the roots and base of the plant are healthy.  Stem canker can be caused by one of two different fungi:  Diaporthe phaseolorum var. caulivora (northern) and Diaporthe phaseolorum var. meridonalis (southern).  Infections by both fungi occur during the vegetative stages during rainy weather, which we had plenty of this year.  Seed infection can also contribute to this disease as well as heavy soybean residue.  Host resistance is the key management strategy and in fact it has been a long time (> 10 years) since we have had fields with reports of high incidence.

Source : osu.edu