Organic Gardening – Southern Blight and Heirloom Tomatoes

Southern blight is the common name for a disease caused by the fungus Sclerotium rolfsii. Other names for this disease include crown rot and white mold. It is a disease problem only in warm climates. In recent years, however, incidents of the disease that is present in both warm and cool climates And the fungus will overwinter under snow or mulch.

Unfortunately this disease has a host range of approximately 200 different genera that include ornamental plants and field crops. Some of the most common host plants include the daylily, astilbe, hostas, peony, phlox, ajuga, delphinium and potatoes.

The first symptom usually noticed is the yellowing and wilting of lower leaves. These leaves will die back from the tips down and very succulent stems will fall over. The fungus will typically attack the plant just at or under the soil line. Sometimes a dark brown lesion can be seen on the stem before other symptoms are visible. The fungus produces a large amount of pure white, thread-like material called mycelium. This material can grow up a plants stem and spread across the soil infecting other plants in the garden.

If this disease hits your garden, controlling it can be a real challenge. Having a good healthy organic garden soil structure to grow healthy strong plants is the best method in controlling disease in your organic garden. Preventative measures like keeping your garden clean of all spent plant debris and the proper disposal of infected plants are among the best practices to use to defend your garden from disease.