Conker Tree Science

Researchers at Newcastle University and the Centre for Ecology & Hydrology, who have been studying the spread of the leaf miner moth (Cameraria ohridella) moth, are turning their attention to what can be done to limit the damage it is causing across the UK.

Through the UK-wide citizen science project Conker Tree Science, they are asking the public to help record where damage caused by the leaf miner moth has occurred and if they can find evidence of birds feeding on infected trees since there is some evidence that garden birds such as blue tits have developed a taste for the caterpillar.

Since 2002, the number of horse chestnut trees affected by the leaf miner moth, has increased significantly across the UK. The highly invasive moth was first recorded in London in 2002 and quickly spread. It is now present in the majority of the trees throughout England and Wales, and the first observation of it in Scotland was recorded in 2015.

Its caterpillars mine within the leaves and destroy most of the leaf tissues, turning the foliage brown and causing leaves fall prematurely. There can be hundreds of thousands of caterpillars in a single infested tree.

While the leaf miner caterpillar does not kill the tree, it weakens it and makes it vulnerable to other diseases in particular bleeding canker, which can be fatal. It can also cause a significant reduction in the size of conkers.

Birds as natural pest controllers

Dr Darren Evans, Reader in Ecology and Conservation, Newcastle University, explains: “The leaf miner moth is really damaging to horse chestnut trees. We know that they can result in trees producing much smaller conkers, and many horse chestnut trees are being cut down and not replaced due to the scale of the threat from insect pests and disease.

“Conker Tree Science has helped to show that the moth has spread very quickly and until now, natural predators such as parasitoid wasps and birds have been slow to respond.

 “Through the Conker Tree Science website, people can record where they’ve seen an infected tree, the amount of damage caused and how many leaf mining caterpillars have been attacked by birds.

 “If we find evidence that birds can be effective natural pest controllers, we might be able to limit horse chestnut leaf miner damage by installing nest boxes on or close to horse chestnut trees.”

Part of our culture

Dr Evans co-founded the Conker Science website with Dr Michael Pocock, researcher at the Centre for Ecology & Hydrology. Set up in 2010 to help track the spread of the leaf miner moth, the aim of the project now is to undertake longer-term monitoring of the damage caused and to analyse the significant amount of data generated by citizen scientists.

Dr Pocock added: “Although it’s not native to the UK, horse chestnuts are now a distinctive and much-loved part of our culture. And while we can’t stop the leaf miner moth we might be able to limit the damage it causes.

“In addition to encouraging natural predators, one of the other ways to limit the spread of the moth is for gardeners and local councils to clear the fallen leaves away in the autumn and dispose of them since this is where the moths over-winter. As part of Conker Tree Science, we are asking members of the public to record what is under the trees so that we can examine the rate of damage the following year.”

As well as the website, there is also a smartphone app that can be used to upload records of damage caused by the leaf miner moth.