Horse Chestnut Leaf Miner
In the garden: Horse chestnut trees
Throughout England, but spreading north and west. Also in Europe.
The horse chestnut leaf miner is a small moth, dark reddish brown in colour, with white fronds. It has an 8mm wingspan and lays its eggs on the leaves of the white flowered horse chestnut tree. The eggs hatch into larvae that burrow into the leaves and feed on the cells within. This causes characteristic ‘mines’ across the leaves. Heavy infestations will cause the leaves to turn brown and give the appearance of the tree in autumn.
The cells within the leaves are destroyed and the leaves are unable to photosynthesize. Trees are not killed by these unsightly infestations although heavy infestations will result in smaller conkers being produced.
Damage caused to horse chestnut trees is mainly cosmetic although it will lead to smaller conkers being produced. Some amenity areas are having their horse chestnut trees replaced with species that are not affected by these types of pests.
Affected leaves can be removed and incinerated when they are easily accessible.
Horse chestnut trees have been shown to adapt to heavy infestations by increasing the hydraulic efficiency of their wood.