The Plant Clinic has received reports of sedum that has rotted at the lower stem and crown. Initially, we had no sample to provide a positive diagnosis. However, a recently received sample, along with telephone calls from several different locations, suggests that this disease is likely occurring in at least the central part of the state.
Colletotrichum stem rot, also called sedum stem rot, is caused by an anthracnose fungus called Colletotrichum. Plants collapse or wilt, drawing attention to the crowns. The lower stems of these plants appear white with mycelia and pinhead-sized fruiting bodies of the fungus. With the aid of a hand lens or dissecting scope, you can see black hairs (setae) of the fungus in these white areas. Masses of spores appear around the hairs when conditions are humid. The fungus overwinters in plant debris in the soil.
Cultural practices and environmental conditions should be reviewed to plan disease management. Moisture promotes infection, and rain and wind spread the fungal spores. Stems on crowded plants are also more likely to become diseased than well-spaced plants that dry more quickly. Sedums withstand drought very well but do not tolerate wet conditions. Suggested cultural controls are to thin plants, minimize the use of mulches around the plants, and ensure good soil drainage. Grow sedums in full sun where there is good air circulation. Destroy all infected plant parts.
We do not have a chemical listing for sedum in the University of Illinois recommendations. On other herbaceous hosts with anthracnose, we find some products with fairly general labels. Such fungicides will protect healthy plants but will not eradicate the disease. Fungicides are most effective in the spring, and will prevent overwintering spores from infecting healthy foliage.