Southern Blight
A plant collapses suddenly in hot weather, and at the soil line there is a fan of coarse white threads spreading over the stem and the ground around it. Scattered through that white mat are round tan to reddish-brown beads the size of mustard seed, which is the one sign that separates it from white mold, whose resting bodies are black and irregular.
Disease checklist
Four things to look for. If most of them match what you are holding, you are in the right place.
What gets rid of it
Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.
1Remove the plant and the soil around it
Dig out the collapsed plant plus several inches of surrounding soil while the tan beads are still on it, and bin the lot.
Try this first2Solarise the bed
Cover moist bare soil with clear plastic through six to eight weeks of high summer, which is one of the few things that reduces the sclerotia.
clear plastic sheeting 4 mil soil solarization3Keep mulch off the stems
Pull organic mulch back from the crown of hostas, daylilies and tomatoes, since the fungus feeds on damp organic matter against the stem.
4Bury residue deeply or remove it
The sclerotia need oxygen near the surface, so turning residue more than 4 inches down or taking it away both help.
garden spade digging fork5Rotate away from susceptible crops
Follow an outbreak with corn or a grass cover crop rather than tomatoes, peppers, beans or peanuts.
cereal rye cover crop seed
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Which plants get southern blight
Every plant we cover that gets southern blight, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same disease can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.
perennials4
Plant families hit hardest
Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Solanaceae, with 3 of the 9 affected plants.
- Solanaceae3 plants
When to treat
Once the stem is girdled the plant is gone and no fungicide will save it, and very few varieties of anything have real resistance, so the management is removal, rotation and soil solarisation rather than a spray.
Timing only — the label is the law
This page tells you when to watch for southern blight and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.
- Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
- Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
- Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
- Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.
Other problems on the same plants
If a plant gets southern blight, these are the problems it most often gets as well, so they are worth checking for while you are out there. They tend to appear together; one does not cause another.