Is this fungus harmful to me?

Powdery mildew is not toxic to humans, but it makes the plant look unsightly. It is best to wash any leaves well if you plan to handle them.

Should I cut the whole plant down?

Only if the infection is severe and the plant is failing. Usually, removing the worst leaves is enough.

Prickly lettuce: spots, causes and fixes

Check these first

Rub the white spot to see if it wipes off like dust.
Check if the plant is crowded by other vegetation.
Observe if the spots appear after a period of high humidity.

Likely causes

Powdery Mildew
Most likely
How to tell: You will see a white or gray powdery coating on the surface of the leaves. It often starts as small spots and spreads to cover the entire leaf.
What to do: Improve airflow by thinning out nearby plants or moving your lettuce to a sunnier spot. You can spray the leaves with a mixture of one tablespoon of baking soda in a gallon of water.
Fungal infection
Possible
How to tell: The leaves may turn yellow or brown and eventually drop off if the infection is severe. The plant will look generally unhealthy and weak.
What to do: Remove and dispose of the most infected leaves to stop the fungus from spreading. Avoid watering from overhead to keep the foliage dry.

Leaf spots on other plants

Find out what's wrong with your prickly lettuce

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

Small amounts of mildew are common in late summer, but you should worry if it covers most of the plant. If the leaves are turning brown and brittle, the damage is likely permanent.

Stopping it coming back

Ensure your plant gets plenty of direct sunlight and avoid wetting the leaves when you water.

Prickly lettuce: spots? Check yours with a photo

Every plant is a little different. Take a photo of your prickly lettuce and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.

Get the app · Or check it from a photo now, free

Questions people ask

Is this fungus harmful to me?: Powdery mildew is not toxic to humans, but it makes the plant look unsightly. It is best to wash any leaves well if you plan to handle them.
Should I cut the whole plant down?: Only if the infection is severe and the plant is failing. Usually, removing the worst leaves is enough.

Guides to these causes

Powdery Mildew

Why does my prickly lettuce have white spots?