0 = no symptoms
1 = lesions on lateral branches only
2 = lesions on main stem, no wilt, and normal pod development
3 = lesions on main stem resulting in plant death and poor pod fill
As you scout your fields, the more plants that are rated as a 3 would indicate a increased severity of white mold in the field.
What does this all mean in terms of potential yield loss? Previous studies across Wisconsin has indicated that for every 1% plant mortality, yield loss is 0.25-0.50 bushels per acre. So, for example, if there was 10% plant mortality, yield loss may be from 2.5 to 5 bushels per acre.
For further information, a new video available through UW-Extension YouTube discusses symptoms and risk factors associated with white mold.
Grau, C.R., Radke, V.L., and Gillespie, F.L. 1982. Resistance of soybean cultivars to Sclerotinia
sclerotiorum. Plant Dis. 66:506-508.