Acute oak decline

Identification and taxonomy of bacteria associated with the acute oak decline (AOD).

Native oak species in Britain are being attacked by a disorder known as Acute Oak Decline (AOD). UWE Bristol scientists, Dr Carrie Brady and Professor Dawn Arnold, are now working in collaboration with Dr Sandra Denman of the Centre for Forestry and Climate Change and the charity Woodland Heritage to investigate the causes of this devastating disease.

AOD is characterised by stem bleeding from vertical cracks between the bark plates, and tissues underlying the bleeding patches are stained and necrotic leading to the formation of cavities in the inner bark. Larval galleries of the bark boring buprestid Agrilus biguttatus are frequently found in close proximity to the necrotic tissue.

Over the past three years, numerous Gram-negative bacterial strains have been isolated from necrotic lesions on symptomatic oaks at a number of sites in Britain. Many of these strains have been identified as belonging to the family Enterobacteriaceae, and have been classified as novel species or subspecies in the novel genera Gibbsiella and Lonsdalea, respectively. A number of bacterial strains still require formal identification and a few which do not belong to any validly described genus or species must be characterised and correctly classified.

Additionally, pathogenicity trials are in progress to try to identify which of these bacteria are responsible for causing AOD with the long term aim of developing treatments and stopping the spread of this disease.

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