Observatree 2022 breaks all records!

What happened in 2022?

Post pandemic, we opened volunteer recruitment for the first time since 2019. We recruited 100 new volunteers who received induction training from Woodland Trust, and pest and disease training from Forest Research tree health scientists. The volunteers joined us in March and hit the ground running!

Throughout the year, Observatree volunteers submitted 4899 tree health reports. Our best year to date. Not only that, volunteers also submitted the most pest and disease reports, they surveyed the most tree species in a single year and monitored the most sentinel trees. Sentinel trees are individual trees that the volunteers visit regularly to track their health.

What do the data tell us?

The data are used to monitor for new pest and disease introductions as an early warning system. They are also used to monitor distribution, spread, hosts, and symptoms of existing introduced pests and diseases.

Chalara ash dieback was the most reported priority pest and disease during 2022 – and has been for since 2016! Phytophthora lateralis and Phytophthora austrocedri were not reported at all last year, which is often the case as they are less common and can be difficult to spot.

A total of 675 individual sentinel trees were monitored across the UK by Observatree volunteers. Again, our largest annual figure to date! Within this network, 61% of the monitored ash, and 59% of the horse chestnut, have been reported with a pest or disease. This is maybe unsurprising due to the widespread distributions of ash dieback and horse chestnut leaf miner. However, 36% of pines were also reported displaying symptoms of ill health – perhaps due to the dry weather we experienced last year. It will be interesting to see how the health of these trees compare this year as we may start to see the impacts from the drought in 2022.

As usual, our most recorded trees were oak, ash, beech, and birch. Additionally, hawthorn was a popular tree this year, with 106 records, the highest to date. Oak takes the crown once again for all surveys and for registered sentinel trees, as our most recorded species, perhaps reflecting its iconic and treasured status.

Reports of trees with Observatree Priority pests or diseases are also submitted through TreeAlert where tree health colleagues at Forest Research diagnose the case based upon the information provided.

What did volunteers submit to TreeAlert and Forest Research?

Ana Perez-Sierra, Forest Research

Observatree volunteers submitted a total of 270 reports to the Tree Health Diagnostic and Advisory Service (THDAS) in 2022 and on 35% of the samples provided we diagnosed and confirmed the presence of pests and diseases that are a priority for Observatree. Most of the reports were submitted via TreeAlert (98%), with the majority from England (72%) followed by Scotland (17%) and then Wales (11%).

Observatree volunteers submitted the highest number of reports during the months of May (41), June (44) and July (61). Different pests and pathogens were reported on 27 different host tree species. The top ten reported hosts were oak (54), ash (36), sweet chestnut (24), pine (21), elm (21), beech (17), horse chestnut (13), rowan (10), spruce (10) and cedar (7).

Five priority pests were encountered: Elm zig-zag sawfly (19), Oriental chestnut gall wasp (18), OPM (6), horse chestnut leaf miner (4) and great spruce bark beetle (1).

Five priority pathogens were reported: Chalara ash dieback (25), European mountain ash ringspot-associated virus (9), AOD (7), Sirococcus blight of cedar (3) and Dothistroma needle blight (2).

Thank you!

Our volunteer network has had such a fantastic year, I’m so excited to see what we do next. This just leaves me to say, thank you. Thank you to all our wonderful volunteers who survey our trees, woods and forests for pests and diseases. Without you, Observatree would not exist.

Read more about this record-breaking year in our annual review available below.