The science behind Observatree

Observatree is a tree health citizen science project, and science is a vital part of what we do. Our volunteers submit tree health data that contributes to our understanding of the changing distribution patterns and impacts of tree pests and diseases. As well as knowing where they are found, it’s equally important to understand where they’re not found, as this also helps us to understand how quickly they’re spreading. In some cases we keen to learn where they may be disappearing from to support ongoing work by colleagues from Fera Science Ltd investigating the effects of a biological control on the Oriental chestnut gall wasp.

Individual trees can also be impacted by climatic events such as drought or flooding, perhaps influencing their susceptibility to pests or diseases, which may themselves be impacted by the weather. Regular information on the distribution of tree pests and diseases therefore helps to inform our understanding of the dynamic relationships between the tree host, the pest or disease and the surrounding environment.

Citizens supporting tree health science
Observatree volunteers have also supported tree health research more directly, for example when colleagues at Forest Research and at Fera wanted to know whether any oak or plane lacebugs or a nematode that has been associated with Beech leaf disease were present in the UK. In both cases volunteers collected samples for analyses by FR and Fera scientists respectively, supporting their ongoing research. I’m pleased to say that neither the nematode nor either of the lacebugs were found.

Exchanging information about the latest tree health science or discoveries is a two-way process and our scientific colleagues regularly update our volunteers on tree health news, research findings and discuss to what extent Observatree could / should support surveillance activities. Within Observatree, we review our list of Priority pests and diseases on an annual basis in consultation with a number of tree and plant health professionals to help ensure that the project is supporting their needs. But not all new pests or diseases of concern are well-suited to citizen science. For example, discoveries in recent years of the eight-toothed spruce bark beetle Ips typographus and the disease Phytophthora pluvialis led to targeted surveillance activities by tree and plant health professionals. Both can be difficult to correctly identify without detailed microscopic or laboratory analysis, so they were not considered to be appropriate Priority pests or diseases for Observatree volunteers to identify. Instead, we asked our volunteers to focus on the host tree species and to submit reports via TreeAlert of both healthy tree locations and areas where trees were looking unhealthy. In the latter cases, volunteers would describe the symptoms and experts would review the finding and then decide if follow-up surveillance is required or not. Our volunteers are keen to help and make a difference, and being able to draw upon the skills of the network is a significant strength of the project.

Science supporting tree health citizens
Our scientific team also lead on the delivery of pest and disease training for our volunteers. Working closely with tree health scientists within Forest Research and plant health scientists at Fera, Observatree’s Scientific co-ordinator (Matt and his predecessor Suzy) pull together the latest pest and disease information and use it to produce our training resources. This is partly why our resources such as the pest and disease identification guides are so popular, not only with our volunteers, but with foresters, arboriculturists, tree and woodland owners and managers. These freely available, highly illustrated resources have become a trusted go-to source of information for many. Our volunteers have access to an online Forum where they can post tree health-related questions. Many are answered by volunteers within the network, but the Forum is also monitored by scientists from both Forest Research and Fera Science, allowing specialist contributions pathologists, entomologists, virologists, bacteriologists, nematologists and others as necessary.
Tree health reports where pests, diseases or an unknown agent that are submitted through TreeAlert are reviewed by many of those same scientists who go on to diagnose the problem. In many cases, this can be done from the information and photographs supplied. Sometimes, a volunteer is contacted and asked if they could collect a sample from the tree or its surrounding soil, allowing further laboratory testing to identify the issue. Our diagnosticians work with our volunteers to get to the cause of the problem, increasing the experience and confidence of the volunteer. The diagnosticians regularly feedback to Observatree colleagues on what is being reported, how frequently, and how accurately thereby informing future training needs for our volunteers.

Tree Health science investment
In recent years, Defra has invested in a new tree health laboratory at Forest Research, designed to allow scientists to research regulated pests and diseases in a controlled way. In addition the creation of a mobile laboratory that can be taken to different parts of Britain where pests and diseases can be examined on-site allows a more rapid analysis. Most recently, there was a significant redevelopment of TreeAlert to facilitate the capture of tree health information from more people. Observatree volunteers played (and continue to play) a significant role in the redevelopment of the system, drawing upon their user experience to guide some of the design aspects of TreeAlert. Citizen science is not new. And the role that society can play in helping to protect trees and other plants was also acknowledged this year in Defra’s Plant Biosecurity Strategy for Great Britain. But perhaps Observatree, with its science-focused training and dedicated volunteer network is exploring new methods of co-design and collaboration between project staff and our volunteers, who are an important and valued part of the tree health team, consolidating the link between citizens and science.