Horse chestnut leaf miner was first discovered in Wimbledon (London) in 2002 and has since spread throughout the country. Although not detrimental to the trees health they can (at high population) destroy most of the leaves causing discolouration and defoliation before the usual fall of autumn and in some cases make them more susceptible to other infections such as bleeding canker. Trees will usually flush as normal the following spring. The appearance can cause alarm to the public.
Larvae from the moth Cameraria ohridella feed from inside the leaves.
Leaves will appear white at first but will soon turn brown and shrivelled, usually from around June onwards.
Caterpillars may be visible within the mined areas especially if the leaf is held to the light.
Trees that are heavily infected may lose all of their leaves prior to autumn.
Burning any fallen leaves in autumn will help reduce any pupae. Alternatively you may wish to bag the leaves for compost but these should be kept closed until July, by this time the adult moths should have died. Pheromone traps for the moths may be used, this may reduce mating and help control levels.
Some Chestnuts such as Aesculus indica or Aesculus x neglecta seem to suffer only minor damage if any at all.
Although there are no requirements to report Horse Chestnut leaf miner, monitoring its spread can certanily help with research
For more information on Horse Chestnut leaf miner please visit forestry.gov