Pythium Root Rot (Damping-Off, Seed Rot) (Peas) Description: A watery rot is characteristic. Plants are often stunted and light green because of the lack of root development. Solution: Plant as early in the season as possible. Peas are a cool-season crop, while pythium disease is most severe at temperatures from 64°-75°F, which is higher than preferred for pea germination. Sprinkle SoilGardTM Microbial Fungicide over seed at time of sowing, before covering seed with soil.