Conker Tree Science

For the past decade, Conker Tree Science has mobilised citizen scientists across the UK to not only map the spread of the highly-invasive horse chestnut leaf-mining moth (Cameraria ohridella), but to try to find out why they are spreading using imaginative ‘missions’. We call this ‘hypothesis-led citizen science’ and it’s an exciting and engaging way of including people in live science experiments, moving beyond simply adding to national datasets.

With initial support from the BES and then the Natural Environment Research Council, we set up the Conker Tree Science website and trained enthusiastic volunteers across the country to go into schools to run ‘Mission: Pest Controllers’ with about 2000 school children. Our hypothesis was that one of the reasons why the leaf-mining moths were spreading so rapidly was due to a lag in the response of natural enemies, in this case tiny parasitoid wasps. These sorts of questions are difficult to test without lots of people power. So the school children were asked to pick a horse chestnut leaf, bag it and record the number of adult moths and/or parasitoid wasps that emerged after a little while. Based on the success of this simple task, we then rolled out ‘Mission: Alien Moths’ which anyone could take part in.

By pooling the data collected by over 3,500 people, we were able to show that within 3 years of the moth arriving in a given area the damage to horse chestnut leaves was high. We discovered one reason why the moth appears to be spreading so well is because the natural pest-controlling wasps are just not occurring in large enough numbers. The work was published in a freely-accessibly journal that has been read by more than 14,000 people to date. Since then, we pioneered a smartphone app for more people to track the spread and have run further ‘missions’. The project is still live, with data collected and stored at the UK’s Biological Records Centre. Conker Tree Science was a finalist in the National Coordinating Centre for Public Engagement 2014 ‘Engage Competition’ and highlighted by UKRI as an example of research impact.



Pocock, M. & Evans, D. (2013) Conker Tree Science: Public Engagement and Real Research. In: Bowater, L. & Yeoman, K. Eds. Science communication: A practical guide for scientists. Chichester: Wiley-Blackwell publishing pp 254-256.

Pocock, M.J.O. & Evans, D.M. (2014) The Success of the Horse-Chestnut Leaf-Miner, Cameraria ohridella, in the UK Revealed with Hypothesis-Led Citizen Science. PLoS ONE 9(1): e86226

Other publications

Pocock, M., Evans, D., Straw, N., & Polaszek (2011) The Horse-chestnut Leaf-miner and its parasitoids. British Wildlife, 22: 305-313.