Disease

Southern blight

A hot-weather soil fungus that rots stems at the soil line, with white threads and mustard-seed-like balls.

What you'll see

• Plants wilt and collapse suddenly in hot weather, often one stem at a time.
• Coarse white fungal threads fan out over the stem base and nearby soil or mulch.
• Round tan to brown balls, the size of mustard seeds, form in the white growth.

Why it happens

A soil fungus that thrives in hot, humid weather attacks over 500 kinds of plants, including tomatoes, peppers, hostas and many perennials. It survives for years as hard little balls and spreads on soil, water, tools and plants.

How to fix it

1. Remove wilted plants with their roots, the white growth and the mulch around them, and bag them.
2. Don't compost them; the seed-like balls survive composting.
3. Turn the soil deeply to bury the survival balls.

Keep it from coming back

• Keep the soil pH above 6.5 and add compost to beds regularly.
• Inspect new plants and their soil for white threads or seed-like balls before planting.
• Don't move soil from infected beds on tools or boots.

Sources

• University of Maryland Extension: Southern blight of vegetables
• Missouri Botanical Garden: Crown rot of perennials (southern blight)
• University of Maryland Extension: Southern blight disease on flowers

General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.