Horse Chestnut Leaf-miner Cameraria ohridella
on infested Horse Chestnut leaf, October 2010
It would seem that the health and safety wallahs are getting a helping hand in their crusade to ban conkers from the nation's playgrounds in the form of a tiny moth with a big name, the Horse Chestnut Leaf-miner. This moth was unknown in Britain prior to 2002 when the first examples were found in Wimbledon, since then it has expanded alarmingly and is now found commonly all over south-east England. It lays its eggs on Horse Chestnut trees and the larvae burrow into the leaves, hence the name, and eat them from within. The damaged leaves cannot photosynthesise the photons from sunlight which they need to grow and if a particular tree is heavily infected, as several of the 30 or so Horse Chestnuts in the Lower Lea are, then it will ultimately die. At the moment the moths have no known predators to keep them in check , obviously opportunistic birds will pick them off but a single large tree could probably produce several thousand moths, so this problem could prove very difficult to resolve unless nature comes up with its own solution, perhaps in the form of a parasite to keep the numbers down. The worse case scenario is that the Horse Chestnut could go the same way as the English Elm, decimated by two species of 0phiostoma fungi spread by the Elm Bark Beetle. A mature Horse Chestnut in full flower is a wonderful sight and a quintessential part of the English spring it would be such a tragedy to lose it.