Septoria Leaf Spot
Dozens of small round spots about an eighth of an inch across, each with a dark brown border and a pale tan or grey centre. Hold a hand lens to the centre and you will see tiny black dots like ground pepper, which early blight never has, and the spots stay small and separate instead of merging into ringed patches.
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.
1Mulch to block splash
Cover bare soil around the plants with straw or shredded leaves so rain cannot fling spores upward.
straw mulch for garden bedsTry this first2Remove the spotted lower leaves
Snap off and bin affected leaves as soon as you see them, and work only when the foliage is dry.
3Water low and early
Use a soaker hose at the soil surface in the morning so leaves are never wet overnight.
drip irrigation kit for garden4Protectant fungicide
Chlorothalonil, copper or mancozeb applied preventively and renewed after rain, per the label.
garden fungicide chlorothalonil5Clean up and rotate
Clear all plant debris at the end of the season and move tomatoes to a different bed for two years, since the fungus overwinters on old stems and stakes.
6Disinfect stakes and cages
Wipe or soak metal stakes and cages before reuse, and replace old wooden stakes that hold the fungus.
isopropyl alcohol spray bottle
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Which plants get septoria leaf spot
Every plant we cover that gets septoria leaf spot, 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
biennial1
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 Asteraceae, with 3 of the 9 affected plants.
- Asteraceae3 plants
- Apiaceae2 plants
- Cornaceae2 plants
When to treat
Start protecting when the first fruit sets or when you find spots on the lowest leaves, because sprays guard clean foliage only and a leaf that is already speckled will not recover.
Timing only — the label is the law
This page tells you when to watch for septoria leaf spot 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 septoria leaf spot, 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.