Horse chestnut trees being damaged by moth

A moth which damages horse chestnut trees is on the advance across Ireland and Britain, scientists have said.

The leaf-mining moth, Cameraria orhidella — whose larvae eat into leaves producing brown blotches and can be so numerous that the tree’s leaves turn brown so it looks like autumn has come early — first arrived in London in 2002.

It had reached Newcastle by 2010, where it temporarily stopped, but it was recorded in Dublin in 2013 and in Belfast last year.

The first and only recording so far in Scotland was also made last year near Loch Tay in September.

Scientists have launched a mobile app called LeafWatch, and are asking for members of the public to contribute sightings of leaf-mining moth infestations in horse chestnut trees to help map its spread.

Despite being only the size of a grain of rice, the horse chestnut leaf-mining moth has a significant impact, affecting the vigour of trees which produce smaller conkers, although there is no clear evidence it affects the overall health of the tree.

Michael Pocock, organiser of the Conker Tree Science project and an ecologist at the UK’s Centre for Ecology & Hydrology, said: “New records of damage caused by the leaf-mining moth are really valuable to help us understand the way it is spreading.

“We are interested to know where it is, and where it isn’t. We need people to get involved right across the country and so created this citizen science app so that anyone can contribute to science.”

Darren Evans, co-organiser of the Conker Tree Science project and a reader in conservation biology at the University of Hull, said: “All records are valuable, however take care not to confuse the damage caused by the leaf-mining moth with a fungal leaf blotch.

“The irregular brown blotches of the fungal leaf blotch are always ringed with yellow, something that is never seen on the leaf-miner blotches.”

Horse chestnuts are a popular tree in the UK, despite not being native to Ireland or Britain, and have been widely planted in parks and gardens since Victorian times, providing generations of children — and adults — the chance to play conkers.

People can submit records of the presence or absence of leaf-mining moths via the LeafWatch app or online at


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