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Horse chestnut leaf miner

The horse chestnut leaf miner is a butterfly of the leafminer family and lives mainly on horse chestnut trees.

recognize Horse chestnut leafminer
Horse chestnut leafminer, photo: Bj. schoenmakers - CC Public Domain
recognize larvae Horse chestnut leafminer
Larva (caterpillar) Horse chestnut leafminer, photo: Beentree - CC BY-SA 3.0

Horse chestnut leafminer (Cameraria ohridella) is a butterfly of the leafminer family (Gracillariidae) and lives mainly on  the common horse chestnut (Aesculus hippocastanum).
The butterfly is about five mm in size, is from China and was first observed in Europe (Macedonia) in 1985. The butterfly has since spread throughout Europe.
The somewhat yellowish larva (caterpillar) is a few mm in size feeds on the mesophyll in the leaves of the tree, damaging the leaves and inhibiting growth. Infected leaves are covered in small brown spots that quickly spread all over the tree and give the tree an autumnal appearance. The damage caused by Horse chestnut leaf miner consists of the leaves turning brown (autumn colour) and is mainly aesthetic: the tree does not die.
The butterfly tolerates severe frosts and has few natural enemies in Europe. Tits eat the larvae, but cannot prevent large-scale damage (autumn colors in August) caused by an infestation.

Where to find

Control

Remove infested leaves.

Prevention

Provide a tit-friendly environment: great and blue tits eat the larvae of the Horse chestnut leaf miner.
Wind a sticky strap around the trunk of the horse chestnut: it forms a natural barrier to stop females of the Horse chestnut leaf miner, among others, from crawling up the trunk.
Hang a pheromone trap in the horse chestnut tree. This trap catches the males of the Horse chestnut leaf miner. As a result, fewer females are fertilized so fewer harmful larvae (caterpillars) are formed.