Should I use a fungicide?

Usually, you do not need one. Removing the infected leaves and fixing your watering habits is almost always enough to stop the problem.

Can I save a leaf with spots?

It is better to remove it. Once a leaf is damaged by fungus, it will not heal, and removing it helps protect the rest of the plant.

China aster: spots, causes and fixes

Check these first

Inspect the undersides of leaves for tiny insects.
Check if the soil is staying wet for too long.
Look for fuzzy growth on the spots.

Likely causes

Fungal leaf spot
Possible
How to tell: You will see dark, irregular patches that may have a yellow halo around them. These spots often appear after periods of heavy rain or overhead watering.
What to do: Remove the affected leaves immediately to stop the spread. Water only at the base of the plant to keep the foliage dry and improve air circulation by spacing your plants 12 to 18 inches apart.
Aphid damage
Possible
How to tell: Tiny yellow or pale spots appear where aphids have been feeding on the sap. You might see the insects themselves or a sticky residue called honeydew on the leaves.
What to do: Spray the plant with a strong stream of water to knock the aphids off. If they persist, apply insecticidal soap once every 5 to 7 days until they are gone.

Find out what's wrong with your china aster

The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

When to worry

Worry if the spots are spreading rapidly across the entire plant or causing leaves to drop. A few small spots on older lower leaves are usually just a sign of aging.

Stopping it coming back

Keep the foliage dry by watering at the soil level and ensure your plants have plenty of space for air to move between them.

Keep your china aster healthy from here

Save your plant in Pocket Botanist and you get care reminders timed for this plant, plus a care history that shows what worked. Identification and a health check are free.

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Questions people ask

Should I use a fungicide?: Usually, you do not need one. Removing the infected leaves and fixing your watering habits is almost always enough to stop the problem.
Can I save a leaf with spots?: It is better to remove it. Once a leaf is damaged by fungus, it will not heal, and removing it helps protect the rest of the plant.

Why are there spots on my China aster leaves?