TreeAlert Demystified: What happens when you submit a report?

A variety of insect pests and pathogenic fungi, bacteria and viruses pose an increasing threat to UK trees and associated ecosystems and monitoring them has never been more important. In the UK TreeAlert is the tailor-made online reporting system and puts users in direct contact with the Tree Health Diagnostic Advisory Service (THDAS) at Forest Research.

A question the THDAS team are often asked is, ‘What happens when I send in a TreeAlert enquiry, how does it all work?’ Here, we pull back the curtain on what goes on behind the scenes!

Submitting an enquiry to TreeAlert:

When you see an unhealthy tree there are a few important things to do before submitting an enquiry to TreeAlert; first take clear pictures, showing the tree in context, the symptoms in context and symptoms in detail (fig. 1). Next make a note of the location of the tree (an OS grid reference), and finally add any contextual comments about your concerns. You’re then ready to submit your enquiry via TreeAlert.

Triage and enquiry allocation

When the enquiry arrives at Forest Research the symptoms in the images and described in the comments are used to allocate the report to the appropriate pathology or entomology diagnostician.  Enquiries north of the River Humber are allocated to the Northern Research Station near Edinburgh, enquiries to the south go to Alice Holt Lodge in southern England.

Initial digital inspection

The diagnostician reviews visible symptoms in the images and considers any additional information provided. If the diagnosis is relatively obvious (with the use of experience and literature resources), a response is emailed to the enquirer with their diagnosis, general facts about the pest or disease and links to additional resources.

If an enquiry is more complex, ambiguous, or potentially a UK priority pest or disease we will often ask for further images and/or a sample of the organism or affected area. However, if the potential diagnosis is particularly concerning (e.g. a quarantine level pest) we may contact the enquirer to arrange a field visit as soon as possible.

Sample processing - entomology

Whether this is foliage, bark or wood, the sample is carefully examined for creatures, evidence of feeding, or their excrement (fig. 2). Once we have our suspect(s), we can attempt to identify them to species level, inspecting its key features and often using taxonomic keys to help identify the species. If the sample is of the insect itself, we can go straight to an identification. If we are not able to reach a conclusive diagnosis, the last resort may be to send the insect or associated larva or excretions for molecular analysis where hopefully the species is identifiable from the DNA sequences.

This whole process from start to finish can be completed within one week, if all goes smoothly, but can take longer if molecular analysis is required.

Sample processing – pathology

The four main sample types that path receive are foliage, bark panels, soil, and large fungal fruit bodies. Foliage it is initially scrutinized under the microscope for fungal fruiting bodies and if present they are extracted, stained, and their structures inspected. In some cases, this is enough to identify to species level using identification keys. However, some cases may require a little more work!

Samples like bark, lesions on foliage, and some fruiting bodies require culturing to get a species level identification. Pices of material from where the pathogen is most active, known as the ‘live-dead junction’ are placed onto a nutrient rich media for the fungi to grow and are checked after three days. If the fungal growth resembles the suspected pathogen, a section of the fungus is chopped out and grown in isolation (fig. 3).

The final stages of processing involve molecular identification, using DNA sequencing to identify the fungal culture to species level.

This whole process can take around 2 weeks from when the sample arrives, although it should be noted that some fungal species are easier to grow than others.

Concluding response

Once a diagnosis is reached, the diagnostician sends a concluding email to the enquirer and the identified pest or disease is added to the TreeAlert database. The email will usually include their diagnosis of the species, background information on its biology and status in the enquirer’s area, as well as helpful resources with further information.

The importance of the growing volume of data added to the database should not be underestimated. Not only is it useful to inform monitoring, management and policies surrounding pests and diseases, TreeAlert also fosters public interest in tree health and the natural environment. The effectiveness of TreeAlert depends entirely on people who care about Britain’s trees and woodlands and who want to help protect our habitats from damaging pests and diseases. Every enquiry counts!