Problems of Sedum

Plants Lanky; Poor Flowering - Soil too Rich
Since sedums prefer sandy, relatively poor soil, soil that is too rich or that has been over-fertilized may encourage excessive development of the foliage, resulting in lank, top-heavy plants with few flowers. Do not add any fertilizer to the soil of these plants. Better yet, try to move the plants to a location with a poorer soil.

Plants Suddenly Die Out - Overspread
Occasionally sedum plants, especially ground covers like Goldmoss suddenly die out, leaving bare patches. This is usually because they have spread too much or become too crowded. It is a simple matter to start new sedums in the spots by working the soil a bit and then scattering leaves from existing plants over it. They will root easily and fill in the bare spot.

Leaves Yellowed and Distorted - Aphids
Aphids are soft-bodied, pear-shaped insects, about the size of the head of a pin. They may be green, brown, or pink. They cluster on tender new shoots and stems to feed, sucking sap from the sedum leaves, causing discoloration and distortion. Leaves turn yellow or brown, and wilt under bright sunlight. Control a light infestation by spraying the leaves vigorously with water. Do this early in the morning for 3 consecutive days. If this doesn't solve the problem, spray the clusters of aphids with insecticidal soap every 2 to 3 days for 2 weeks. As a last resort, use pyrethrum spray.
For more information see file on Dealing with Aphids.

Ragged Holes In Leaves - Slugs and Snails
Slugs are actually snails, but without protective shells. They are 1 to 2 inches long (some species grow up to 8 inches). Their coloration ranges from white to gray, yellow, and brown-black. Plants attacked by slugs and snails suffer large ragged holes in leaves and stems. Although these pests are usually attracted to moist, well-mulched gardens and acidic soil, they occasionally feed on succulent sedums. They are active at night, rasping holes with their file-like tongues in leaf and stem surfaces. They hide under boards or leaf litter during the day. Control by trapping them in a plate baited with beer. The slug is attracted to the yeast in the beer, climbs in, and drowns. Set out traps at the first sign of holes in sedum leaves.
For more information see file on Dealing with Slugs and Snails.

Stems Rot at Soil Line - Crown Rot
Crown rot caused by a soil-dwelling fungus causes sedums to decay at the soil line. There is no permanent cure for crown rot. Remove infected plants and the soil around them. Discard them in the trash to avoid spreading the fungus. Do not replant sedums in that area for a year or two. Thoroughly cultivating around neighboring plants allows the soil to dry out and helps prevent the spread of the fungus.
For more information see file on Dealing with Fungal Disease.

Dead Blotches on Leaves - Leaf Blotch
Botrytis gray mold attacks sedum leaves and flowers, causing blotches to form. Eventually, the leaves and flowers turn brown and die. Cut off and discard all diseased plant parts and destroy entirely any badly infected plants. Spray infected plants with a copper or sulfur based fungicide, making 2 applications 5 days apart.
For more information see file on Dealing with Fungal Disease.

Powdery Spots on Leaves - Rust
Powdery spots on leaf undersides signal rust, a fungus disease. Rusts seldom harm sedums, but the spots are unsightly. Remove and destroy infected leaves. If the infestation is serious, destroy diseased plants and all debris before growth starts in the spring. Control weeds in and around the garden, as they can contribute to rust problems. To prevent rust, spray plants periodically with wettable sulfur, beginning several weeks before you expect this disease to appear. Space plants widely to allow air to circulate among them, and avoid wetting the leaves when watering.
For more information see file on Dealing with Fungal Disease.