On the 1st of October 2013, a new tree health citizen science project was launched under the name of Observatree. In the wake of concerns over ash dieback, a number of government tree and plant health scientists and inspectors joined with two charitable Trusts to create a partnership designed to increase our capacity for tree health surveillance by working with volunteers. And here we are, 10 years later.

Protecting our nations trees from harmful pests and diseases is all about early detection which allows swift and targeted action. As Defra’s Chief Plant Health Officer, I take great comfort from the fact that we have a well-trained and highly capable network of eagle-eyed volunteers who are out and about looking out for signs of tree health problems. The volunteers are a highly valued asset, and I’m grateful to each and every one of them, for all their work in protecting our trees. Defra have invested significantly in the Observatree project over the last 10 years, and I am very proud of the project’s many achievements.

To put this work into context citizen science has been an integral part of our approach to Tree health policy over the last 10 years. Earlier this year Defra published The Plant Biosecurity Strategy for Great Britain (2023-2028) which sets out the joint approach that Defra, the Scottish and Welsh Governments and the Forestry Commission will take to plant biosecurity for the next five years. In the strategy we outline our work and activity on citizen science and how valuable this is in helping us to fight pests and diseases. Our extensive UK surveillance programme on Tree Health involves government, industry, conservation groups and the public, and the specialised ‘Observatree’ network are a vital part of this work.

Where it all began

To support official surveillance activities, Observatree was established to determine whether a network of specialist volunteers could be trained in the identification and reporting of pests and diseases of concern. And in the summer of 2015, an Observatree volunteer reported Oriental chestnut gall wasp to the north of London when it was believed to only be present in Kent, thereby altering our understanding of the distribution of the pest and how long it had probably been in the UK.


Nine project partners are at the heart of Observatree and our shared visions for the project has helped to ensure its continuation. In recent years, we have expanded our networks, to collaborate with other organisations that are helping to raise awareness of tree health. Observatree is not the only citizen science project with an interest in tree health and we are working with the Tree Health Citizen Science Network to share news, results, updates and guidance with others, seeking opportunities to collaborate, support and promote the important role that everyone can play in tree health monitoring.

Our Priority Pests and Diseases

There are many tree pests and diseases with the potential to cause harm to the UK’s trees, but some can only be identified through careful analytical methods. It is therefore necessary to identify a short-list of Priority pests or diseases that were both of concern and could potentially be identified on site by members of the public. Each year, Observatree works with tree and plant health scientists and inspectors to review this Priority list. We now have 24 pests and diseases to our Priority list.


Training and managing our volunteers

We offer a lot of training for our volunteers in how to survey for, and identify the Priority pests and diseases, how to report them. And how to do so in a bio-secure way that doesn’t help to spread any pests or diseases further. We proactively manage and engage with our volunteer network, encouraging the reporting of tree pests or diseases throughout the calendar year. But this does mean that we are only able to support a small network with a maximum capacity of 200. Some have been with the project since it began and are well-known to project staff, adding to the sense of the Observatree ‘family’.

The science behind Observatree

The latest scientific information about tree pests and diseases of interest is at the heart of Observatree’s activities. Some of the UK’s leading tree and plant health experts are also those who help to train our volunteers and produce our educational resources. Observatree works in close collaboration with our scientific colleagues, often supporting their tree health research by participating in additional surveillance or associated tasks. Ensuring that the Observatree resources are underpinned by the latest information and their free availability on the Observatree website makes them a valued and trusted resource that are used by many people.


Addition of Sentinel trees and Host of the Month

In 2017, we introduced the concept of Sentinel trees to the project. These are individual trees chosen by our volunteers to represent common tree species of interest to the project. Our volunteers regularly check on the health status of these trees and provide regular updates on changes in their condition. The Host of the Month initiative focuses on a specific species of tree, encouraging our volunteers and others to report any associated pests or diseases, or trees of that species that appear to be healthy.


Our dedicated volunteers – The heart of Observatree

We are very lucky within Observatree, as we have some very dedicated volunteers. Observatree is a collaboration between our volunteers and project staff. Many project developments or tasks are undertaken with input from the volunteers, some of whom have written blogs for our website, presented at internal webinars, and spoken about their role at conferences. They have access to an online discussion area where they can share knowledge, experience, answer questions and support each other. This mentoring aspect prompted us to create a Lead Volunteer role for some of our more experienced members of the team.

Volunteers on a mission – individuals can make a difference

We appreciate all the reports submitted by our volunteers. But some have ‘gone the extra mile’, often becoming specialists in a particular pest or disease or submitting large numbers of reports. For example, one volunteer submitted more than 130 reports of ash dieback in many in parts of Wales, making a significant difference to our understanding of its distribution. We have nine volunteers who have been with us since the first days of the project. And 64 who have been with us for at least four years. Thank you to all our volunteers, past and present who have, and continue to support our work.


Diagnosing the problem

Tree Alert is the online mechanism by which our volunteers and members of the public submit information about an unhealthy-looking tree. When Tree Alert reports of suspected pests or diseases are submitted, the information is passed to scientists at Forest Research for confirmation or an alternative diagnosis. During the first six months of 2023, 28% of the TreeAlert reports received by Forest Research were submitted by Observatree volunteers, with Oak processionary moth being reported the most.  


Making a difference – 20,000 reports and still counting

Since it began, Observatree volunteers have submitted more than 20,000 tree health reports. Roughly 75% of these relate to healthy trees. Observatree has become an important part of Britain’s approach to tree health and this is reflected in the 2023 Plant Health Biosecurity Strategy for Great Britain where there is an aim to have a society that can help to reduce the risks for plant pests and diseases. Whilst the Observatree volunteer network continue to do their routine monitoring and surveillance, the network can also be called upon to support official activities, helping to increase the eyes on the ground and potentially preventing the next pest or disease from becoming established.