Walks | Environment | Schools | Local notes | Links | Supporters | Wednesday Volunteers
Events | News | Newsletter | Downloads | Contacts | Members| Archive| EASI
Trees |
Horse Chestnut Leaf MinerMany of you will have noticed that our horse chestnut trees are looking decidedly sick these days. By late summer the leaves are covered in whitish then brown blotches. These are the leaf mines of the caterpillars of an alien moth species – the horse chestnut leaf miner (Cameraria ohridella). The following information is from Forest Research and Butterfly Conservation.
Sick looking trees can be caused by other problems. Damage by the fungus Guignardia aesculi can give rise to a superficially similar blotch to the mine of the moth but these are not translucent when held up to the light. Significant dieback of branches in the canopy, or death of horse-chestnut trees, is caused by other factors, e.g. bleeding canker of horse chestnut, or a combination of factors. Trees showing these symptoms need to be checked by a qualified arboriculturist so that appropriate management can be undertaken. Where the moth is established, the safest and most practical means of control is to remove fallen leaves during the autumn and winter. C. ohridella over-winters as a pupa in the fallen leaves, and commercial composting of leaves or burning them (if local regulations allow) destroys the pupae and reduces the moth population in the following spring. Composting is less effective when leaves are collected into smaller heaps, as in gardens, because temperatures in small heaps are too low to kill the pupae. More information can be found at Forest Research and Butterfly Conservation, and the UK Moths website. |