Sedum, a perennial also known as stonecrop, is popular both for its hardiness and its enormous flowers. Since sedum is drought-resistant and can grow in a variety of adverse conditions, it is a nearly ubiquitous landscape perennial that makes gardeners' lives easier by returning to grow and bloom each year with little to no coaxing or coaching. However, there are some diseases that can tackle your sedum and destroy it if you are not on the lookout for the signs and symptoms. Knowing what types of disease threaten your sedum will help you keep your landscaping happy and healthy.
Mold and Mildew
Sedum can fall prey to gray mold and powdery mildew. Gray mold causes a gray, fuzzy growth on the sedum plant and tends to spread rapidly along leaves and stems. Over time, it can blight the entire plant. Powdery mildew looks more like chalk dust and may be black, gray, white or even pink. Both of these infections can usually be controlled by removing the affected parts of the plants using sterile pruning techniques, and disposing of the debris in a garbage bag rather than dropping it on the ground. However, if the problem persists, treat mold and mildew with a thiophanate-methyl fungicide. Prevent mold and mildew by planting it in a location where it gets several hours of sun a day, and using a drip hose in the early morning.
In sedum, stem rot is caused by an infection by Sclerotium rolfsii. You will first notice that the flowers are yellowing and wilting. As the infection progresses, the rest of the plant will also wilt and die. You may be able to spot a white, threaded mass growing on the stem where it enters the ground. Once a sedum plant has stem rot, you must remove it and the soil surrounding it as quickly as possible to prevent the spread of the infection. The plant that has contracted stem rot cannot be saved. Prevent stem rot by making sure the soil is well-drained. Water when the ground is dry, and only in the early morning. Do not water periodically throughout the day or to the point where the ground becomes muddy.
Leaf Spot and Rust
Leaf spots are dark spots that appear on the tops of the leaves, while rust spots are rusty orange, black or brown lesions that form underneath the leaves. Both issues create serious problems for sedum if they are allowed to spread and coalesce, at which point they can overrun the plant and kill it. If you only see a few spots, remove the affected part of the plant and dispose of it completely to contain the infection. Treat both infections with sulfur if they persist. Like most sedum diseases, leaf spots and rust tend to appear when conditions are moist throughout the day, or when the soil is not well-drained.