Bacteria: Advancement of Control and Knowledge to Save Threatened Oak and Protect them for Future Generations

Iconic British oak are under threat from Acute Oak Decline (AOD) typified by stem bleeds, bacterial lesions and larval Agrilus biguttatus. The beetle-bacteria relationship is unclear and controversial, and until resolved beetle trapping as a control cannot be implemented. 1. The role of Agrilus in introducing and transmitting bacteria, and adult and larval beetle chemical interactions with bacterial metabolites, and underlying genetic mechanisms, will be assessed. 2. Data on drought impacts will guide stress management. 3. Public/stakeholder perceptions to management will inform policy and uptake of practical management. 4. Other broadleaf host susceptibility to AOD will be tested. Transmission microcosm experiments will detect presence of bacteria from adult beetles, eggs and larvae using metabarcoding, RT-PCR and culturing methods. Introduction and spread in stems will assess larval chemotaxis to bacterial semiochemicals, and lab and field behavioural assays and coupled gas chromatography-electrophysiology (GC-EAG) will assess adult beetle responses. Transcriptomics will evaluate Agrilus x bacterial tests for gene upregulation linkages between Agrilus and bacteria. Druoght effects will be tested in a field trial where drought and wounding by ring-barking (as a proxy for nutrient and water stress) and host & microbiome responses (metabolomics and RNA-seq) determined. High-resolution metabolomics (LC-MS/MS and GC-to-MS profiling) and Random Forest machine learning modelling will identify metabolites. Values and attitudes of a diverse group will be examined in relation to oak engaging with citizen scientists and land managers to gather data for evidence base for decision making. Finally, we will assess cross infectivity potential of AOD bacteria and investigate other bacterial species in unresolved tree cankers. Results will guide future management practices in terms of beetle control, tree stress management and cross infectivity of bacteria.