What is Southern Blight?
Southern blight, southern wilt, southern stem rot, and southern root rot all refer to the same disease. It is caused by the soil borne fungus Sclerotium rolfsii. The disease attacks a wide range of vegetable crops and ornamental plants at or below the soil line. Southern blight on plants is most likely to occur in the summer months when the soil is warm and moist. Symptoms include discolored lower leaves, wilted foliage, and plant collapse and it usually results in the death of the plant. Upon close inspection, you may find an abundance of white hyphae or mycelia around the lower stem and roots and in the surrounding soil. When you find the hyphae or mycelia, the best course of action is to dispose of the plant and the soil surrounding it.
How Do You Control Southern Blight?
Controlling southern blight in the home garden is a challenge because the fungicides that are effective in treating the disease are only available to commercial growers. Home gardeners must depend on cultural practices to control the disease. In the home garden, southern blight treatment begins with good sanitation to prevent the spread of the disease. The disease organism travels around the garden in bits of soil that clings to garden tools and the soles of shoes. Remove the soil before moving from one part of the garden to another. Quarantine new plants by growing them in a bed that is isolated from the rest of the garden until you are sure they are disease-free. Remove and destroy diseased plants, along with the surrounding soil and any garden debris or mulch that has come in contact with them. Don’t transplant any nearby plants to other parts of the garden. Soil solarization is an effective method of killing the fungus in the south, but in northern climates, the soil temperatures may not be high enough to eradicate the disease. Cover the soil with a clear plastic tarp and leave it in place while the heat builds up under it. The top two inches (5 cm.) of soil must come to a temperature of at least 122 degrees F. (50 C.) to kill the fungus. If all else fails, consider calling in a landscape professional to treat your garden soil with the appropriate fungicides specified for southern blight treatment.
