Sedums, also called stonecrops, are perennial flowering plants with succulent foliage. Many different types of sedums exist, some growing to only 2 inches tall and others reaching 2 feet or larger in height. Sedums' flower colors vary in shades of white, yellow, pink and red. Sedums are low-maintenance plants that are susceptible to only a few fungal diseases, most of which are prevented by planting the sedums in well-draining soils.
Stem rot disease is caused by the fungus Sclerotium rolfsii and is one of the most common diseases that affect sedums. Stem rot causes the sedum's lower leaves to turn yellow and white, cotton-like growths of mycelium to appear around or near the crown on the soil. Eventually, the whole plant will wilt and die. Treating stem rot can be difficult and in severe cases may involve replacing all of the soil. Control stem rot in the sedums by cutting away and destroying all the diseased or symptomatic plant parts.
Basal or Root Rot
Basal rot is caused by the fungus Rhizoctonia solani. This fungus rots and collapses the basal stems and turns them black or brownish. Root rots are caused by Fusarium fungi species and produce similar symptoms that are more centralized in the sedum's roots. Most fungicides are not effective in treating either basal or root rot. Remove and destroy sedums infected with these types of rot.
Powdery mildew (Erysiphe spp. fungi) causes white powdery spores to cover the sedum's leaves. This fungal disease is most prevalent during humid conditions when there is little rainfall. Treat powdery mildew by applying an appropriate fungicide, such as potassium bicarbonate, triadimefon or thiophanate-methyl, to your sedums according to the instructions on the label.
Several different leaf spot diseases can infect sedums, including those caused by the fungal species Cercospora, Colletotrichum and Septoria. Leaf spots appear as lesions or as decomposing or necrotic patches on the sedum's leaves and occur most often during wet conditions. Apply fungicides like thiophanate-methyl or sulfur to control leaf spot diseases on your sedums.
Gray mold, also known as Botrytis blight (Botrytis cinerea), is a fungal disease that causes a fuzzy gray mold to grow on the sedum's damaged or old flowers and leaves. The gray mold spreads to the healthy plant parts as the disease progresses. Gray mold disease is most prevalent during cool, wet environmental conditions and when old flowers or damaged plant parts remain on the sedum, providing an entry point for the fungus. Remove all the dead or dying flowers from the sedum to prevent gray mold. If your sedums are already infected with gray mold, apply an approved fungicide like thiophanate-methyl.
Rust diseases are caused by several fungal species belonging to the Puccinia genus. Sedums with rust diseases have powdery and rust-colored spore growths on their leaves and stems with yellowed surrounding plant tissues. Control rust diseases by applying an appropriate fungicide to your sedums, such as mancozeb or sulfur.