Observatree, is a collaborative project led by Forest Research, and partner organisations including the Forestry Commission and the Woodland Trust. Using citizen science it aims to help spot new pest and disease threats to UK trees. A set of 20 booklets is now available in printed ringbound A5 format, making them particularly useful in the field. These were designed for volunteers monitoring priority pest and diseases. Whilst not intended as complete descriptions, they are nevertheless useful to both tree workers and more generally for those wishing to improve their knowledge of particular diseases and to recognise associated symptoms. The high resolution colour photos accompanying the descriptions are well chosen, showing both macro features and more detailed aspects of pathology.