Tree Health reports submitted by Observatree volunteers
2023 was another good year for the Observatree project, with our volunteers submitting just over 4000 tree health reports, including our first data from the Shetland Islands. It is important to note that approximately 25% of these relate to trees that show no signs of pest or disease and are believed to be healthy. Whilst the map below shows data submitted by Observatree volunteers, anyone can now submit data on heathy trees by registering on TreeAlert and following the steps for adding Healthy trees.

A further 2345 reports are of the 635 Sentinel trees that were monitored by the Observatree volunteers during 2023. And reassuringly, the majority of these Sentinel trees were also believed to be healthy. The healthy reports provide important baseline information on where pests and diseases are thought to be absent, allowing researchers to assess rates of pest or disease spread into new areas.

The Observatree volunteers submitted more than 600 reports on trees of concern. Of these, 240 related to pests or diseases on our Priority list. Oak processionary moth was reported the most (70) and we also had our highest annual number of Elm zigzag sawfly reports (30). In Scotland, the Observatree volunteers continue to track the progress of chalara dieback of ash and the horse chestnut leaf miner as they move north. Outside of our Priority list, the Observatree volunteers also report other suspected pests, pathogens, or unknown signs or symptoms of ill health. This wider surveillance provides valuable information on other pests or pathogens and has the potential to highlight something unexpected.

Increased networking

During 2023, we relaunched our Host of the Month initiative, designed to help new Observatree volunteers to ease into the project by focussing on one species of tree each month and its associated pests and diseases. As part of this relaunch, we are making the Host of the Month resources available to everyone via the Observatree website. Each month, my colleague Matt Parratt posts a Host of the Month blog on our website with all of the information that you need to know. We are keen to share the Observatree resources with other groups, working with them to raise awareness of tree health and promote reporting through TreeAlert.

Towards the end of 2023, we put a new collaborative agreement in place with PlantNetwork and the Botanic Gardens Conservation International (BGCI), to raise awareness of tree health across new garden audiences both across the UK and beyond. Those of us in the Observatree project look forward to developing this new collaboration during 2024 and creating further agreements with others as we continue to expand our networking.


Enhancements to TreeAlert

2023 also saw a significant redevelopment of TreeAlert, the tool for reporting tree pests and diseases in Britain. Whilst the tool remains a web-based system, it now has an adaptable display that will allow it to work on different screen sizes and many mobile devices. Users are able to see more information about the trees that they have reported and mechanisms were added to allow trees that appear to be free of pests or diseases to be recorded. Further enhancements are being investigated that are intended to provide wider feedback on the data previously submitted to TreeAlert.



Observatree has grown over the past ten years. We have many experienced tree health volunteers within our network and this experience continues to develop in others. We continue to expand our reach, working with many groups and organisations. And we review our list of Priority pests and diseases, developing and updating training resources on a regular basis. These activities will continue throughout 2024, but we are also looking into other possible mechanisms to share more tree health training with wider audiences. We are excited by the opportunity that working with will bring and look forward to sharing the next phase of TreeAlert developments with the Observatree volunteers.