Plant Pathology: Extension: Plant Disease Library

Sclerotinia

Important diseases:  Dollar spot, Camellia flower blight, Stem rot of numerous vegetables, ornamentals, and some field crops.

Sclerotinia stem rots may be confused with those caused by the fungus Sclerotium. The disease common name, "white mold," has been used to describe diseases caused by both fungi. However, the two fungi are most easily identified by the size, shape and color of their sclerotia produced within the white mycelial growth.

Dollar spot symptoms on turf are small, bleached or straw-colored spots approximately 2-inches in diameter. Spots may grow together into large irregular patches of affected turf. White, spider web-like growth of mycelium (fungal threads) can be seen in the early morning when dew is present. Fluffy, white, cottony-mold (mycelium) covers lower stems, flowers and leaves of stem rot infected plants. Sclerotia (survival structures) are often formed internally in infected stems or flowers and are not seen unless the tissue ruptures or is cut open. Infected stems or plants wilt and die.

Sclerotia are usually formed internally within stems or flowers and therefore take on the shape of the tissue surrounding them. This results in irregularly-shaped, initially white sclerotia that later turn hard and black. Spores (ascospores) are produced within tiny, cup-shaped mushrooms (apothecia) that grow out of the sclerotia usually in the spring.