Pythium is the most important damping-off fungus. It also causes seed rots, root and crown rots, and soft rots. It has an extremely wide host range. Pythium is a water-mold and is favored by saturated soil conditions and high soluble salts. Black lesions may be present on affected stems.
Rots are watery and slimy in nature.
Affected roots are soft and honey-brown in color. A diagnostic feature of Pythium infection is the sloughing of the outer root cortex leaving only the thread-like root stele intact. Oospores and sporangia can be seen within infected plant tissue. If tissue is stained with acid fuchsin, spores will stain pink. Pythium can be easily confused with Phytophthora .