Cercospora Leaf Spot
Small round spots with a pale tan or grey centre ringed by a distinct purple, red or dark brown border, often so many that the leaf looks freckled. On beet and chard the thin centres eventually fall out and leave holes, and the purple rim is what tells it apart from the plain brown spots of other leaf blights.
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.
1Pick off and bin spotted leaves
Remove the worst lower leaves early so there is less spore source to splash upward.
Try this first2Water the soil, not the leaves
Switch from a sprinkler to a soaker hose and water in the morning.
soaker hose 50 ft3Space and thin for airflow
Thin beet and chard rows and prune crowded hydrangea stems so the leaves dry quickly after rain.
4Autumn cleanup and rotation
Clear all leaf debris in fall and keep beets, chard and spinach out of that bed for two years, because the fungus overwinters on the residue.
5Protectant fungicide if it is severe
Chlorothalonil, copper or mancozeb applied preventively on the labelled interval, mainly worth it on a beet or chard crop rather than a shrub.
garden fungicide chlorothalonil
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Which plants get cercospora leaf spot
Every plant we cover that gets cercospora 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.
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 Amaranthaceae, with 3 of the 7 affected plants.
- Amaranthaceae3 plants
- Apiaceae2 plants
When to treat
Act when the first spots appear on the older leaves in warm humid weather, roughly July onward here; it rarely kills a plant, so on hydrangea and crape myrtle it is fair to do nothing but clean up.
Timing only — the label is the law
This page tells you when to watch for cercospora 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 cercospora 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.