Sclerotinia stem rot first appears as watersoaked spots, usually at the point where stems attach to branches, or on branches or stems in contact with the soil. A white cottony growth of fungal mycelium develops on the lesions, and infected tissue becomes soft and watery. The fungus may spread rapidly to nearby stems and leaves if moisture is present for several hours. Lesions then may expand and girdle the stem, causing the foliage to wilt. During dry conditions, lesions become dry and will turn beige, tan, or bleached white in color and papery in appearance. Hard, irregularly shaped resting bodies of the fungus, called sclerotia, form in and on decaying plant tissues. Sclerotia are generally 1/4 to 1/2 inch in diameter, initially white to cream in color but become black with age. They frequently develop in hollowed-out centers of infected stems. Sclerotia eventually fall to the ground where the fungus is able to survive until the next growing season.
Presence among species
|Sclerotinia sclerotiorum||Solanum tuberosum|