A description of the symptoms of Acute Oak Decline in Britain and a comparative review on causes of similar disorders on oak in Europe

Acute Oak Decline (AOD) is a relatively new decline-disease affecting both native oak species (Quercus robur and Q. petraea) in Britain. The key aim of this study was to describe the symptoms, and signs of AOD, to set a baseline. The second aim was to compare and review the European literature on what appear to be similar disorders on oak. AOD is characterized by four key features: weeping patches more-or-less vertically aligned on oak tree trunks; cracks between bark plates from which dark fluid seeps; inner bark necrosis and the presence (in >90 per cent of cases) of larval galleries of the oak buprestid, Agrilus biguttatus, on the phloem–sapwood interface. In this study, it was noted that although larval galleries were present in the inner bark in 19 of 21 trees, the ‘D-shaped’ exit holes of the adult beetles were seen less frequently on bark plates of affected trees (33 per cent of cases). Similar disorders reported in Europe are compared with AOD in Britain and potential causes of the condition discussed. Based on the unmistakable symptoms, it is hypothesized that AOD is a distinctive, identifiable condition within the broader oak decline syndrome.