Horse Chestnut Leaf Miner
This was the first survey undertaken in a pilot of TreeWatch during 2010.
This is a straightforward survey - we ask volunteers to record simply whether the leaf miner is present or absent just once during the year.
about the survey
pest - horse chestnut leaf miner Cameraria ohridella
The horse chestnut leaf miner Cameraria ohridella is a leaf mining moth. The moth grows up to 5 mm long and flies in the Spring. Its larvae (caterpillars) feed on the leaves and cause the brown blotches seen on leaves from the Summer onwards. Infected leaves become covered in small brown patches which will spread rapidly across the whole tree. Infected trees can look autumnal in appearance.Cameraria ohridella was first found in the UK on Wimbledon Common in July 2002. The rate of spread since seen in the UK is about 40-60 km (24-37 miles) a year. Its main impact is a visual one, causing infected trees to look in poor health and to prematurely loose their leaves.
There is no evidence from the European mainland that the leaf miner causes a decline in tree health but it is possible that differences in our climate or interactions with other pests and diseases might lead to greater impact in the UK. It is important that we monitor the effects of the moth and its interaction with other pests and diseases, especially bleeding canker of horse chestnut.
read more on the Forest Research website...
how you can help
We want your help in surveying horse chestnut trees for the leaf miner parasite.
Please complete the box(es) below once that you have checked your tree(s) to see if the parasite is present or absent.
Details and indications of the leaf miner are described below.
host tree - horse chestnut Aesculus hippocastanumThe main host of the horse chestnut leaf miner in Europe is the white-flowering horse-chestnut Aesculus hippocastanum. This species is heavily damaged in areas where the moth is present. Other species of Aesculus can be affected although some are resistant.
The horse chestnut grows to 25m (82 feet) tall and its large white flowers in May are the showiest of any large tree in Britain. It produces the conkers that children play with in the Autumn.
The horse chestnut belongs to a family of some 14 different species. About half of the 14 species have white flowers, just like the horse chestnut we are surveying, although these are less common in Britain and mostly confined to collections in arboretums and parks.
The easiest way to identify a horse chestnut is if you have known the tree for some time and have seen it produce conkers. You may find the old husks lying on the ground from the previous Autumn. The husks around the conkers of horse chestnut are spiny, whilst for the Japanese and Indian horse chestnuts they are smooth.