Horse Chestnut Leaf Miner and Conkers
Introduced Asian Moth Damaging Horse-chestnut Trees.
Feb 12, 2007
The horse-chestnut leaf miner (Cameraria ohridella) is a moth which was accidentally introduced into Europe from Asia in 1985. In England it was first found on Wimbledon Common in 2002.
The larvae burrow into the leaves of the Common Horse-chestnut (Aesculus hippocastanum), causing serious damage. Infected leaves are covered in small brown patches which spread rapidly across the entire tree.
In Asia the moth is naturally controlled by several species of parasitic wasp, but these are not found in Europe. This lack of natural enemies means that the moth can spread without check and it is expected to destroy many Horse-chestnut trees.
Conkers
- Many parts of Europe would miss the Horse-chestnut if the moth ever managed to kill it off. Horse-chestnuts were introduced from their native Greece into Britain back in the sixteenth century, largely for their spectacular flowers and ornamental value.
- Small boys soon realised that the nuts were useful too! These ‘conkers’ soon replaced snail shells in the game of the same name which is played every autumn throughout the British Isles. (Check out the rules, and remember to say ‘obly, obly, onker – my first conker’ as you collect your first one!)
Conkers, Spiders and Medical Folklore
Conkers have several other uses. They are supposed to frighten spiders away. Put a few in the corner of each room your house will remain spider-free for the year, maybe because of the chemicals in the conkers? These same chemicals (saponins, especially aescin) are also reputed to have medicinal properties. They are thought to be effective against piles, rheumatism and varicose veins. Maybe this is why carrying a conker in your pocket is supposed to be lucky?
Sap Run and Beetles
When the bark of the Horse-chestnut is damaged the sap will run out. Fungal infections can interfere with the natural healing process, and when this happens there will be a permanent leakage of sap.
- This is known as a ‘sap run’ and it attracts a number of specialist beetles and other insects who feed on it.
- Some of these beetles even carry their own yeast in little pouches on their legs to help convert the sap into tasty things!
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