HORSE chestnut trees in the Farnham area have been blighted by the same micro-moth that turned their leaves brown last year before autumn had even arrived.

The culprit is the horse chestnut leaf miner. Each year there are three generations of this tiny brilliantly coloured moth, which lays its eggs on the leaves. After the eggs hatch, the caterpillars bore into the leaf and feed on the soft tissue, the sandwich filling between the upper and lower layers, creating brown leaf mines.

“Virtually every leaf on our local trees is now discoloured and crops of conkers are reduced in both number and size, but even so, the trees suffer no long-term damage,” Bourne Conservation Group member David Todd said. “The group is interested in all changes to our biodiversity and has observed the progress of this recent invader.

“The horse chestnut is of course also an invader. It originates from the Balkans and was introduced to Britain in the 1600s. The little moth also comes from the Balkans, where it was first collected in Macedonia in northern Greece in 1984. It was only described scientifically in 1986, being named for Lake Ohrid where it was first discovered.

“Two years later it made a sudden appearance in Austria, and it was first noted in Britain at Wimbledon in 2002. Since then it has been spreading at a rate of 30 to 40 miles a year so that it now occurs throughout England and has just arrived in Scotland.

“Already Nature is balancing these infestations. Birds, such as blue tits, have learnt how to peck holes in the leaves to reach the tiny caterpillars and tiny wasps are beginning to parasitize the caterpillars in large numbers. ”

New members are welcomed to enable the group to keep up with the many community tasks it is undertaking. For more information e-mail [email protected].