Should I spray my tree with fungicide?

Fungicides are rarely practical for large trees. Good sanitation and proper spacing are much more effective.

Will the spots kill my tree?

Usually no. The tree will likely survive, though it may look unsightly for the remainder of the season.

Why are there spots on my horse chestnut leaves?

Check these first

Examine the underside of the leaves for fungal growth.
Check if the spots are spreading rapidly.
Look for fallen leaves around the base.

Likely causes

Leaf blotch fungus
Most likely
How to tell: Small reddish brown spots appear that eventually merge into large dead patches.
What to do: Rake up and destroy all fallen leaves in autumn to remove fungal spores. Prune away heavily infected branches to improve air circulation.
Anthracnose
Possible
How to tell: Dark spots appear along the leaf veins and can cause the leaves to curl or drop early.
What to do: Keep the area under the tree clean of debris. Ensure the tree is not overcrowded by other plants.

When to worry

Minor spotting is common in wet, humid summers and rarely kills a mature tree. Worry if the tree loses most of its leaves before September.

Stopping it coming back

Water at the base of the tree rather than overhead to keep the foliage dry.

Not sure which one it is? Photograph your horse chestnut.

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

Should I spray my tree with fungicide?: Fungicides are rarely practical for large trees. Good sanitation and proper spacing are much more effective.
Will the spots kill my tree?: Usually no. The tree will likely survive, though it may look unsightly for the remainder of the season.