Will powdery mildew kill my astilbe?

It rarely kills the plant, but it can weaken it and make it look unsightly. Treat it early to keep the plant healthy.

Should I throw away infected leaves?

Yes, dispose of them in the trash rather than the compost pile to prevent the fungus from spreading.

Why are there white spots on my garden astilbe?

Check these first

Look closely at the leaves for a white, dusty texture.
Check if the plant is crowded by other foliage.
Inspect the undersides of leaves for other signs of distress.

Likely causes

Powdery Mildew
Most likely
How to tell: White, flour like patches appear on the surface of the leaves and stems.
What to do: Remove the most affected leaves to improve airflow. Apply a neem oil spray or a fungicide labeled for powdery mildew in the evening.
Poor Air Circulation
Possible
How to tell: The plant is crowded by other shrubs or planted in a stagnant, humid corner.
What to do: Prune back neighboring plants to allow better airflow. Avoid overhead watering that keeps the foliage wet for long periods.

When to worry

Worry if the mildew covers most of the foliage, as this prevents the plant from photosynthesizing. Minor spots are manageable.

Stopping it coming back

Space your plants properly to ensure good airflow and water at the base rather than over the leaves.

Not sure which one it is? Photograph your astilbe.

This page lists the usual causes. Pocket Botanist looks at your actual leaf and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

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Questions people ask

Will powdery mildew kill my astilbe?: It rarely kills the plant, but it can weaken it and make it look unsightly. Treat it early to keep the plant healthy.
Should I throw away infected leaves?: Yes, dispose of them in the trash rather than the compost pile to prevent the fungus from spreading.