Is powdery mildew contagious to other plants?

Yes, it can spread through the air to other susceptible plants nearby. Isolate the affected plant until it clears up.

Should I cut off the spotted leaves?

If the infection is severe, removing the worst leaves can help stop the spread. Make sure to dispose of them in the trash, not the compost.

What are these spots on my spotted spurge?

Check these first

Look closely at the white spots to see if they rub off like dust.
Check the humidity levels in your growing area.
Inspect the leaves for signs of moisture sitting on them.

Likely causes

Powdery mildew
Most likely
How to tell: You will see a white, dusty substance on the surface of the leaves. It looks like someone sprinkled flour over the plant.
What to do: Improve air circulation around the plant immediately. You can treat it by wiping the leaves with a mixture of one teaspoon of baking soda in a quart of water.
Water splashing
Possible
How to tell: Small brown or yellow spots appear on the leaves after watering. This happens when soil particles splash onto the foliage.
What to do: Water the soil directly at the base of the plant rather than overhead. Use a watering can with a narrow spout to keep the leaves dry.

When to worry

Worry if the white spots cover the entire plant and cause the leaves to shrivel. Small, isolated spots are usually manageable with better airflow.

Stopping it coming back

Ensure the plant has plenty of space and keep the leaves dry during watering.

Not sure which one it is? Photograph your spotted spurge.

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

Is powdery mildew contagious to other plants?: Yes, it can spread through the air to other susceptible plants nearby. Isolate the affected plant until it clears up.
Should I cut off the spotted leaves?: If the infection is severe, removing the worst leaves can help stop the spread. Make sure to dispose of them in the trash, not the compost.