Climate change and the international plant trade have meant that tree health monitoring and surveillance have become increasingly important issues in the UK. In October 2012, it was announced that Chalara dieback of ash was affecting UK ash trees. In the same month, I started a 3 year project to investigate the role of citizen science in tree health monitoring and the potential of citizens as early-warning systems - examining what motivates people to participate in citizen science and the ways in which their data contribute to the resultant science. 

In this paper, I consider what it means to be ‘in touch’ (Haraway 2008), in a contact zone, with trees, pests and pathogens, specifically how care and response-ability work to turn matters of fact into matters of care and concern. How being in touch with trees might mean that professional and citizen scientists come to care for these nonhumans through first-hand experience. Extending my earlier work on enthusiasm (Geoghegan 2013) as an emotional affiliation,  here scientific facts are regarded no longer as soulless but embodied socialities – revealing the care, love, passion and enthusiasm of scientific endeavor – ‘transforming things into a matter of care is a way of relating to them, of inevitably becoming affected by them, and by modifying their potential to affect others’ (Puig de la Bellacasa 2011, p99).