Pathogen(s) causing disease:

Pythium, Fusarium, Diplodia, Rhizoctonia, Penicillium spp. and other soilborne bacteria.

Symptoms:

The seed rots prior to germination.

Conditions:

Favorable among wet and cool soil growing conditions in the spring. Soil temperatures 55 F or lower favor seed rot because germination is delayed. Seed rot is often more severe in early planted or no-till/reduced tillage fields because of cool soil temperatures. 

Management:

Fungicide seed treatment provides protection for 2-3 weeks. Plant when soil conditions are warmer and drier, and ensure planting depth is not too deep.

Sources:

Purdue University
Iowa State University