In the Plant Disease and Insect Clinic, we are receiving soybean samples with the symptom of physiological scorch.
At this point, most of it is SDS, or Sudden Death Syndrome, but numerous diseases can cause similar symptoms. Regardless of the cause this symptom is indicative of a problem with the vascular system once soybean has shifted to the reproductive phase. Usually “scorch” is the result of a root-rot such as SDS, CBR, dectys stem borer, or Phytophthora root rot.
Spraying a fungicide will not impact these diseases at all and should be avoided.
Below are links to disease notes that will explain how to differentiate these diseases and what action to take in the future.
Frogeye leaf spot, Target spot and Stem Canker
So far this year target spot of soybean and frogeye leaf spot have both been identified in North Carolina.
Many cultivars are resistant to these diseases so there is no cause for alarm at this time. If the disease is detected it warrants a fungicide application.
If target spot is identified it warrants an application of a strobilurin fungicide. If frogeye is identified then a combination fungicide (StrategoYLD, Fortix, Quadris Top, or Affiance) may be warranted since resistance to strobilurin fungicides was identified last year in Beaufort County.
Soybean stem canker has been found in the Piedmont and in Martin County. Soybean stem canker must be controlled with varietal resistance and fungicides rarely impact this disease especially at this point in the season.