Can I spray the caterpillars myself?

No, you should never handle oak processionary moth nests because the hairs are toxic and cause severe skin irritation. Always hire a professional.

Will my tree die if the leaves curl?

Not necessarily, as curling is often a temporary defense mechanism against heat. If the cause is pests, the tree can recover if the infestation is treated quickly.

Why are my sessile oak leaves curling? Causes and fixes

Check these first

Inspect the undersides of leaves and branches for caterpillars or webbing.
Check the soil moisture level at a depth of 3 inches.
Observe if the leaves flatten out when the temperature drops in the evening.

Likely causes

Oak processionary moth
Most likely
How to tell: You will see clusters of caterpillars or silken nests on the branches and trunk. The leaves often look ragged or curled where they have been feeding.
What to do: Contact a professional arborist immediately to handle removal as these caterpillars are hazardous to human health. Do not attempt to touch or remove the nests yourself.
Heat stress
Most likely
How to tell: The leaves curl inward during the hottest part of the day to conserve moisture. If they flatten out at night, the tree is just reacting to the sun.
What to do: Ensure the tree receives deep watering every 7 to 14 days during dry spells. Apply a layer of mulch around the base to keep the roots cool and moist.

Curling leaves on other plants

Find out what's wrong with your sessile oak

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

Be concerned if you see active caterpillars or if the leaves remain curled and brittle even when the soil is moist. It is normal for leaves to curl slightly during intense afternoon heat.

Stopping it coming back

Keep the tree healthy with consistent watering and monitor for early signs of pest infestations.

Sessile oak: curling leaves? Check yours with a photo

Every plant is a little different. Take a photo of your sessile oak 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.

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Questions people ask

Can I spray the caterpillars myself?: No, you should never handle oak processionary moth nests because the hairs are toxic and cause severe skin irritation. Always hire a professional.
Will my tree die if the leaves curl?: Not necessarily, as curling is often a temporary defense mechanism against heat. If the cause is pests, the tree can recover if the infestation is treated quickly.

Guides to these causes

Oak Moth

Why are my sessile oak leaves curling?

Check these first

Not sure what's wrong with your sessile oak?