Amaryllis is a bold, striking flower that grows from a bulb. Many people grow them in containers, often in the fall or winter for late winter to early spring blooms, but amaryllis can also grow outdoors in warmer climates. Amaryllis is generally easy to grow and is not often troubled by disease, but be aware of signs of southern blight and know how to manage it.
What is Amaryllis Southern Blight Disease?
Southern blight of amaryllis is a fungal disease that can affect these plants. The causal agent is the fungus Sclerotium rolfsii. It also causes disease in legumes, cruciferous vegetables, and cucurbits, among many other plants you may have in your garden.
There are a lot of different plants, and weeds, that can play host to the southern blight fungus. For amaryllis, you are most likely to see the disease if you grow them outdoors. Potted amaryllis plants are less vulnerable but could become infected through the soil or contaminated garden tools.
Amaryllis Southern Blight Symptoms
The first signs of southern blight infection are yellowing and wilting of the leaves. The fungus will then appear as white growth around the stem at the level of the soil. The fungus spreads through small, bead-shaped structures called sclerotia, which you may see on the threads of white fungus.
Amaryllis with southern blight may also show signs of infection in the bulb. Look for soft spots and brown, rotted areas on the bulb below the soil. Eventually the plant will die.
Preventing and Treating Southern Blight
The fungus that causes this disease will accumulate in the leftover plant material from past seasons. To prevent the spread of southern blight from year to year, clean up around your beds and dispose of dead leaves and other material appropriately. Don’t put it in the compost pile.
If you grow amaryllis in pots, throw out the soil and clean and disinfect the pots before using them again with new bulbs.
Southern blight of amaryllis can also be treated if you catch it in time. Drench the soil around the stem with an appropriate fungicide. Check with your local nursery for the right treatment for amaryllis.