Horse Chestnut Leaf Miner (Moth: Cameraria ohridella)
The caterpillars enter the leaves and eat the internal tissue, which from mid-June shows as white or brown elongated blotches on the leaves, with extensive damage to the foliage becoming apparent by August. However, there is no evidence that even a heavy infestation causes a decline in the tree’s health as trees re-flush as normal the following spring. As the pupae over winter on the fallen leaves, the only practical way to reduce the infestation is, in Autumn, to collect and burn the fallen leaves.
Horse Chestnut Leaf Blotch (fungus: Guignardia aesculi)
Irregular brown blotches develop on the leaf tips and edges from mid-summer. There are often yellow margins to the blotches. As with the leaf miner the attack is unsightly, but has little affect on the tree’s overall health. The fungus over-winters on the fallen leaves. As with the Leaf Miner, the only practical control is, in Autumn, to collect and burn the fallen leaves.